The Encyclopedia Of Nutrition And Good Health - V docx

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valerian root
(Valerian officinalis; garden helio-
trope; setwall) The root of a perennial herb native
to Europe, North America, and northern Asia that
has been used as a sleep aid and antianxiety treat-
ment for more than 1,000 years. The plant is
inconspicuous except for its small white or pink
flowers and an unusual odor that some have
described as reminiscent of aged cheese. According
to legend, the Pied Piper used valerian to lure rats
from the village of Hamelin.
Valerian is a popular dietary supplement in the
United States and in Europe whose supporters
claim it has a calming effect and can induce sleep.
Reliable research to support these claims does
not yet exist, but the herb does appear to have
some effect on the neurotransmitter gamma-
aminobutyric acid (GABA). Small studies suggest
effectiveness in promoting sleep compared to
placebo. People with nerve disorders that causes
uncontrollable spasms or who suffer from
TARDIVE
DYSKINESIA
have been found to have low levels of
GABA in their brains. Because of the herb’s repu-
tation as an antispasmodic, it has been used for
centuries by women seeking relief from menstrual
cramps. As a food, valerian is classified “generally
recognized as safe.”

Because valerian root is available in the United
States as an herb, its safety and efficacy have not
been tested by the U.S. Food and Drug Administra-
tion (
FDA). However, in high doses valerian root
rarely can cause liver damage with long-term use
or high doses. Some patients who have taken the
supplements have suffered chest pain, heart
arrhythmia, tremors, insomnia, headache, and
blurred vision. With long-term high doses, sud-
denly stopping valerian may be associated with a
withdrawal syndrome. A few reports suggest possi-
ble decreased alertness after valerian use. Women
who are pregnant or nursing should not take this
supplement due to inadequate safety data.
Garges, P. et al. “Cardiac Complications and Delirium
Associated with Valerian Root Withdrawal,” Journal of
the American Medical Association 280 (November 1998):
1,566–1,567.
valine (Val, L-valine) A dietary essential AMINO
ACID
that serves as an important protein building
block. Valine is classified as a
BRANCHED CHAIN
AMINO ACID
, along with ISOLEUCINE and LEUCINE.
The daily requirement for valine is estimated to be
10 mg per kilograms of body weight, similar to the
other branched chain amino acids. Infused
branched chain amino acids are selectively used for

energy by skeletal muscle rather than by the
LIVER.
Branched chain amino acids may help restore mus-
cles in patients with liver disease or in patients who
have undergone physical trauma such as surgery.
However, it is not established that these amino
acids have an anabolic (muscle enhancing) effect
when used as supplements for healthy people.
Valine and other branched chain amino acids
are useful in treating liver damage associated with
ALCOHOLISM (hepatic encephalopathy). They seem
to limit muscle wasting and reduce some of the
neurologic effects related to this disease. Valine and
branched chain amino acids may be useful in treat-
ing amyotrophic lateral sclerosis (Lou Gehrig’s dis-
ease). Levels of these amino acids are low in these
patients. On the other hand, animal studies indi-
cate that an excess of one branched chain amino
acid antagonizes the other two. (See also
AMINO
ACID METABOLISM
.)
vanadium A TRACE MINERAL required by animals
for normal growth and development. Deprivation
of this element causes slowed growth, reproductive
problems and blood abnormalities in rats and
chicks. Vanadium in the form of vanadate and
vanadyl sulfate improves the effect of insulin in
diabetic animals; and artificially induced diabetes
in rats can be reversed by vanadate. Large doses

also affect serum
FAT and CHOLESTEROL levels,
although more research in this area is needed.
There is no
RECOMMENDED DIETARY ALLOWANCE
for vanadium, and the amounts required for opti-
mal health are unknown. Nutritional requirements
would likely be met by levels present in food. Black
pepper and dill seeds are the richest sources. Whole
grains, seafood, milk products, and meat are fair
sources, while beverages, vegetables, and fruits
contain the lowest amounts. The average daily
intake in the United States is about 20 mcg, quite
low in comparison to known essential trace ele-
ments. Elevated vanadium is associated with bipo-
lar disorder, and high levels of vanadium may be
toxic.
vanilla (Vanilla planifolia) A tropical plant that
produces pods containing vanilla, an aromatic
ingredient used as a food flavoring. Vanilla is a
member of a group of tropical orchids, native to
Central America and Mexico. The active ingredi-
ent, ethyl vanillin, is chemically synthesized and
marketed as “vanillin.” Ethyl vanillin has 3.5 times
the flavor intensity of vanilla bean extract. Because
it lacks minor ingredients found in the extract, the
taste is not identical. Vanilla is used to flavor ice
cream, beverages, chocolate, candy, and gelatin.
Vanilla is considered a safe additive. (See also
FLA-

VORS
; FOOD ADDITIVES.)
variant Creutzfeldt-Jakob disease
(vCJD) See
BEEF.
varicose veins Bulging, sinuous veins that are
close to the surface of the skin. Usually the term
varicose veins refers to distended leg veins in which
blood vessels become weakened, permitting blood
to flow backward instead of forward to the heart.
This condition affects an estimated 25 percent of
American women, 10 percent of men, and 50 per-
cent of people over the age of 50. Often, varicose
veins are only a cosmetic issue with no symptoms.
However, symptoms like aching legs can develop
after a person has been standing for a long time.
Leg cramps, swollen ankles, intense pain or tender-
ness along the vein at the end of the day can occur.
Occupations that require extended periods of
standing increase the risk of varicose leg veins.
Pregnancy also increases venous pressure in the
legs and may lead to the development of varicose
veins. Standing places heavy pressure against leg
veins, and the extra weight of the blood stretches
the walls of the vessels, which pulls apart vessel
valves, causing blood to pool in the veins. This
pressure can cause surface vein walls to bulge out
into varicose veins.
Varicose veins can occur anywhere in the body.
Hemorrhoids are a common example; they can be

aggravated in straining during bowel movements
because intense abdominal pressure is transmitted
to all veins, even leg veins. Defective, deeper veins
can become inflamed (phlebitis) and create a blood
clot, resulting in a more serious condition. If the
clot dislodges, it can cause blockage in vessels of the
lung, the heart (
HEART ATTACK or myocardial infarc-
tion), or the brain (
STROKE).
In addition to inheritance, lifestyle and diet are
believed to be predominant factors in the develop-
ment of varicose veins. They seldom occur in pop-
ulations relying on a diet high in unrefined,
fiber-rich foods.
EXERCISE such as walking and bike
riding contract leg muscles that push blood along
the venous system. Increasing the strength of ves-
sel walls may minimize the risk of varicose veins.
Blue-red berry pigments called anthocyanidins and
proanthocyanins can strengthen vessel walls,
reduce capillary fragility and help protect the
venous connective tissue.
BLACKBERRIES, CHERRIES,
and
BLUEBERRIES are rich sources. People who have
varicose veins may also be less able to break down
FIBRIN, a clotting protein that is often deposited
near varicose veins and increases the risk of clot
formation.

CAPSICUM (cayenne pepper), GINGER,
GARLIC, and ONIONS increase fibrin breakdown. (See
also
CIRCULATORY SYSTEM; DIET, HIGH COMPLEX CAR-
BOHYDRATE; FIBER.)
vasoconstriction Reducing the diameter of
blood vessels. Both environmental and physio-
640 vanilla
logic factors can constrict vessels. For example, a
drop in temperature causes vasoconstriction, an
adaptation that helps conserve body heat. All
blood vessels except capillaries and venules are
regulated by the
NERVOUS SYSTEM. Thus fear and
other emotions can reduce blood flow. At wound
sites,
SEROTONIN and other products are liberated
by blood
PLATELETS, cells that stick to the walls of
damaged vessels to form clots. Serotonin helps
reduce blood loss by acting as a vasoconstrictor.
Certain hormones act as vasoconstrictors:
EPINEPH-
RINE
and norepinephrine (released by the ADRENAL
GLANDS
in response to stress) and ANGIOTENSIN II
(formed in the
KIDNEYS in response to a drop in
blood pressure).

vasodilation Increasing the diameter of blood
vessels. Vasodilation increases blood flow and
removes waste products while replenishing oxygen
and nutrients. Decreased oxygen concentration
and the accumulation of metabolic waste products
help expand blood vessel walls. The accumulation
of
LACTIC ACID, decreased pH (more acidic blood),
the buildup of carbon dioxide, and increased blood
ion concentration (osmolarity) dilate blood vessels.
Increased body temperature exerts a vasodilator
effect to help cool the body. During inflammation,
HISTAMINE is released from damaged cells and from
immune cells called mast cells. Histamine is known
to increase capillary leakiness, and fluid leakage
out of capillaries accounts for swelling in areas of
inflammation.
An important family of vasodilators is the
kinins, which represent peptides, whose parents
occur in the blood and in tissues. Kinins resemble
histamine: They relax the smooth muscles around
vessels and increase capillary leakiness and blood
flow through the kidneys. Kinins occur in sweat
glands, salivary glands, and the
PANCREAS. Kinin
release is inhibited by
GLUCOCORTICOIDS, hormones
produced by the adrenal glands. A high protein diet
also increases blood flow in the kidneys.
PROS-

TAGLANDINS, hormone-like substances made from
essential fatty acids, can have similar effects. (See
also
EDEMA; NITRIC OXIDE.)
vasopressin See ANTIDIURETIC HORMONE.
veal BEEF from male dairy calves, ranging in age
from four to 18 weeks. Subtherapeutic doses of
drugs may be used when veal calves are very young;
this treatment is discontinued as the animal’s
immune system matures. Veal, like most red
MEAT,
is a good source of
ZINC and other trace minerals.
The nutrient content of a 3-oz. (85 g) braised veal
cutlet is: 185 calories; protein, 23 g; fat, 9.4 g; cho-
lesterol, 109 mg; calcium, 9 mg; iron, 0.8 mg; thi-
amin, 0.06 mg; riboflavin, 0.21 mg; niacin, 4.6 mg.
vegan See VEGETARIAN.
vegetable oil Edible oil extracted from seeds or
nuts. Plant oils provide
ENERGY, VITAMIN E, and
polyunsaturated
FATTY ACIDS. No vegetable oil con-
tains
CHOLESTEROL because plants do not synthesize
it. Vegetable oils classified as
TRIGLYCERIDES; like
animal
FAT, they contain three fatty acids and GLYC-
EROL (glycerin) and contain just as many calories as

animal fat (nine calories per gram).
Vegetable oils fall into three classes: saturated,
monounsaturated, and polyunsaturated:
1. Saturated vegetable oils are solid at room tem-
perature. The so-called
TROPICAL OILS, palm ker-
nel oil and
COCONUT OIL
, and VEGETABLE
SHORTENING
, a chemically hardened vegetable
fat, are saturated and are solids at room temper-
atures. These saturated fats resemble saturated
animal fat, as in
LARD, BUTTERFAT, and beef TAL-
LOW
. The excessive consumption of SATURATED
FAT
regardless of its source is believed to increase
the risk of
CARDIOVASCULAR DISEASE.
2. Monounsaturated oils including
OLIVE OIL are
rich in a fatty acid called
OLEIC ACID, which lacks
two hydrogen atoms and contains a single dou-
ble bond. Olive oil apparently lowers blood
LOW-DENSITY LIPOPROTEIN (LDL) cholesterol, the
less desirable form, without lowering the “good”
kind of cholesterol

HIGH-DENSITY LIPOPROTEIN
(HDL), and probably lowers the risk of cardio-
vascular disease.
3. Polyunsaturated oils such as
CORN OIL, SAF-
FLOWER oil, SUNFLOWER oil, and SOYBEAN oil con-
tain a preponderance of polyunsaturated fatty
acids. These fat building blocks lack many
hydrogen atoms and contain two or more dou-
vegetable oil 641
ble bonds. High consumption of polyunsatu-
rated vegetables oils apparently lowers LDL cho-
lesterol levels, a desirable result, but also lowers
HDL levels, which is undesirable. High con-
sumption of polyunsaturated oils increases the
need for the antioxidant vitamin E.
Extraction of Oils
The first step in oil extraction involves crushing or
grinding oil-bearing tissue to release oil from cells.
The second step involves pressing to squeeze oil
from crushed tissue. Residues from pressing are
usually extracted with solvents such as hexane to
remove the remaining oil. The solvent is then
removed. To purify these oils, they are further
extracted with alkali and heated, degummed,
deodorized by steam treatment, and decolorized by
treatment with charcoal or clay. Since these proce-
dures remove or destroy vitamin E, synthetic
antioxidants like
BHT, BHA, and PROPYL GALLATE are

often added to retard
RANCIDITY. Oils may be “win-
terized” by removing particulate matter that form
upon chilling.
The assumption that cold-pressed oils have been
extracted from the seeds under mild conditions and
contain more vitamin E and polyunsaturated fatty
acids may not be valid. Cold-pressed oils are often
heated between 120° F and 150° F, then refined,
bleached, and deodorized, processes that can
involve further heating, possibly at temperatures as
high as 450° F.
Certain “unrefined oils” are available. In the
preparation of these oils, processors do nothing to
the oils after heating ground seeds and pressing
them to extract the oils. Because such oils are less
pure, they have distinctive flavors and colors.
Hydrogenation
Unsaturated vegetable oils can be hardened and
stabilized by chemically adding hydrogen atoms to
reduce the degree of polyunsaturation. Hydrogena-
tion increases the shelf-life of an oil by making it
more resistant to rancidity. Heating vegetable oils
at high temperatures does not hydrogenate oils,
nor does it convert them to saturated fat. “Partially
hydrogenated” vegetable oils retain some of their
polyunsaturated fatty acids and remain oils at room
temperature, while completely hydrogenated (sat-
urated) oils are solid at room temperature (veg-
etable shortening). Hydrogenated vegetable oils as

well as partially hydrogenated oils contain chemi-
cally altered fatty acids called
TRANS-FATTY ACIDS;
their long-term safety has been questioned.
Americans generally consume too much fat and
oil, which increases the risk of
HEART ATTACK
,
STROKE
, OBESITY, and certain forms of CANCER.A
person with high blood cholesterol may be advised
to reduce saturated fat intake. Total fat should
account for less than 30 percent of daily calories,
perhaps as low as 20 percent of calories according
to some authorities. To reduce the decomposition
and rancidity of vegetable oils, store oils in the
refrigerator in sealed dark containers. Do not heat
oils any more than is necessary and limit cooking
with oils at high temperatures. Discard cooking oils
after use.
vegetables Cultivated plants that generally pro-
vide leaves, stems, roots, and flowers used as foods.
Leafy vegetables include
SPINACH, CHARD, CABBAGE,
and
LETTUCE. Stem vegetables are CELERY and
ASPARAGUS; BEETS, TURNIPS, YAMS, POTATOES, and
CARROTS are roots and tubers as opposed to stems.
Vegetables like pumpkin, squash,
BROCCOLI, and

CAULIFLOWER are flowers. GARLIC and ONIONS are
bulbs. Corn is a seed vegetable. Vegetables include
several botanical classes, including
TOMATOES
(fruit); PEAS and BEANS (legumes); and MUSHROOMS
(
FUNGI).
Most regions of the world have contributed veg-
etables, as indicated by the following examples:
• Europe, the origin of beets, broccoli,
BRUSSELS
SPROUTS
, cabbage, CHIVE, MUSTARD GREEN, pea,
and turnip; the Mediterranean region:
ARTI-
CHOKE
, asparagus, celery, chard, CHICKPEA,
ENDIVE, KALE, KOHLRABI, OLIVE, PARSLEY, PARSNIP.
• Africa: the
BROAD BEAN, CRESS, OKRA, yam; the
Middle East: broad bean, cabbage, carrot, cauli-
flower,
CUCUMBER, LENTIL, lettuce, mustard
green,
RADISH, SPINACH
• India: EGGPLANT, MUNG BEAN; China: Chinese
cabbage,
SOYBEAN, water chestnut
• Central Asia: beet, chive, carrot,
DANDELION, gar-

lic,
LEEK, onion, pea, shallot, turnip
• Central America: bean, corn, jicama, green
PEP-
PER, PUMPKIN, SQUASH, SWEET POTATO, tomato
642 vegetables
• South America: cassava, corn, lima bean, pepper
potato, sweet potato, tomato
Root vegetables and tubers like yams, sweet
potatoes, carrots, and potatoes are by far the lead-
ing vegetable crops. They provide starch, fiber,
minerals, and some vitamins. Orange-colored veg-
etables like sweet potato and carrot provide
BETA-
CAROTENE. Several of the most popular vegetables
in the United States provide minimal nutrient con-
tent: celery, lettuce, cucumbers. The greener the
vegetable, the more the beta-carotene (provitamin
A) and
CAROTENOIDS it contains. Spinach, collard
greens, dandelion greens, kale, and Swiss chard are
excellent sources and they provide vitamin C, iron,
and calcium.
The consumption of fresh vegetables in the
United States has steadily increased since 1980
from about 115 lb. per person per year to over 190
lb. per year (1990). Nonetheless, fewer than 10
percent to 20 percent of U.S. citizens report eating
the minimum recommended five daily servings of
vegetables and fruits. Potatoes represent nearly 37

percent of all fresh vegetables, and their popularity
accounts in part for this increased vegetable con-
sumption. Much of this increase represents french
fries and baked potatoes eaten away from home;
french fries and baked potatoes with fatty sauces
are high-fat foods, in comparison with baked pota-
toes without toppings. Lettuce, broccoli, tomatoes,
carrots, and cauliflower show increased popularity,
probably a reflection of the increased availability of
salad bars in fast-food restaurants.
There is a growing awareness that vegetables
provide materials besides vitamins and minerals
that are important for long-term health. Some
plant substances (
PHYTOCHEMICALS) are not consid-
ered essential nutrients, yet their consumption can
have long-term effects on reducing the risk of
CAR-
DIOVASCULAR DISEASES, CANCER, CATARACTS, AUTOIM-
MUNE DISEASES like rheumatoid arthritis, premature
senility, and other chronic problems associated
with
AGING. Plants of the cabbage family, including
broccoli, cabbage, and brussels sprouts, produce
materials called
ISOTHIOCYNATES and indoles, which
seem to lower the risk of cancer. Sulfur compounds
of onions, garlic, leeks, and chives seem to boost
the immune system and inhibit tumors. Many
plants including vegetables produce

FLAVONOIDS,a
broad family of substances that can function as
antioxidants to block the oxidative damage to cells
due to free radicals. Free radical-induced damage is
now believed to be a factor in some degenerative
diseases, like heart disease, associated with aging.
For example, dark green leafy and orange vege-
tables and some fruits are a rich source of
CAROTENOIDS
, including beta-carotene. These phy-
tochemicals function as antioxidants and they
enhance the immune system. As a group they
reduce the risk of some forms of cancer.
Rather than a simple ingredient, vegetables pro-
vide a wide array of known phytochemicals;
undoubtedly, many more remain to be discovered.
Phytochemicals appear to be most effective when
supplied in combination with a range of substances
as found in minimally processed foods, including
vegetables. Their effects are often synergistic, that
is, the overall effect of a combination is more ben-
eficial than any one isolated ingredient.
Vegetable Processing
Although fresh vegetables are available year round
due to large refrigerated warehouses and fast trans-
portation systems, processed vegetables remain an
important part of the American diet. A variety of
methods are used to prepare or to preserve vegeta-
bles. Several of the more common methods
include:

Canning Developed in the 19th century in
France, canning remains a major food preservation
strategy. This process involves heating vegetables in
metal or glass containers to a sufficiently high tem-
perature to destroy microorganisms that cause
spoilage or disease. Heat-treated contents are
sealed against air to prevent oxidation.
Drying Drying food in the sun for preservation
has been carried out for thousands of years. Drying
must be carried out rapidly to avoid changes in
nutrients, flavor, or texture. The action of plant
enzymes that darken produce, destroy nutrients
and alter flavor can be limited by blanching (a brief
heat treatment) or by treatment with preservatives
like sulfites or antioxidants such as
VITAMIN C.
Freezing Commercial techniques for rapid
cooling and freezing allow many vegetables to
retain most qualities of fresh vegetables for periods
vegetables 643
lasting up to eight to 12 months. Blanching slows
alterations in flavor, color, and texture of frozen
vegetables.
Pickling Vegetables can be preserved in a salt
solution (brine) or in
VINEGAR, or a combination of
the two. Pickled cucumber and relishes are common
food items. Commercially pickled products require
heating to destroy microorganisms and to inactivate
plant enzymes that alter vegetables properties.

Raw or Cooked Vegetables?
There are certain advantages to eating cooked veg-
etables. Cooking a vegetable can increase the avail-
ability of beta-carotene because it is released from
storage sites in plant cells. Cooking starchy vegeta-
bles breaks down starch granules so they can be
digested. On the other hand there are advantages
to eating vegetables raw. Raw vegetables may con-
tain higher levels of heat-sensitive nutrients
because cooking decreases the content of water-
soluble vitamins. For example, baked potatoes and
sweet potatoes lose about 20 percent of the B vita-
mins and vitamin C. Boiling causes lower losses.
Boiling leaches B vitamins and minerals out of veg-
etables. Losses may be as high as 80 percent.
Steaming and microwave cooking of vegetables
greatly reduces this loss. Boiling also removes vita-
mins and minerals. Note that keeping foods warm
on a steam table increases the loss of vitamins such
as vitamin C, thiamin, and riboflavin.
On the other hand, vegetables that have not
been stored properly, or have been handled care-
lessly, can suffer similar nutrient losses. Slicing,
mashing, dicing, mincing, and grating break veg-
etable cells and expose vitamins to oxygen and
degradative enzymes. Vitamin C is especially sensi-
tive to oxygen exposure. The longer the storage
period for sliced vegetables, the greater the loss of
vitamin C. (See also
BALANCED DIET; DIETARY GUIDE-

LINES FOR AMERICANS; FOOD PRESERVATION; FOOD
PROCESSING
; FOOD GUIDE PYRAMID; ORGANIC FOODS.)
Graziano, J. M. et al. “A Prospective Study of Consump-
tion of Carotenoids in Fruits and Vegetables and
Decreased Cardiovascular Mortality in the Elderly,”
Annals of Epidemiology 5 (1995): 225–260.
vegetable shortening A form of saturated fat,
prepared from vegetable oil, that resembles animal
fat. A major advantage of vegetable shortening is
that, unlike lard, butter, or beef fat, it does not con-
tain
CHOLESTEROL. Vegetable shortening does con-
tain the same high calories as butter or lard,
however. Vegetable shortening is a product of the
chemical processing called hydrogenation. This
process adds hydrogen atoms to unsaturated
FATTY
ACIDS
, thereby converting naturally liquid fat (oils)
to materials with varying degrees of stiffness. Usu-
ally several different fats are blended to achieve the
desired consistency of a shortening.
CORN OIL,
COT-
TONSEED OIL
, SOYBEAN oil, OLIVE OIL
, PALM OIL,
PEANUT oil, SAFFLOWER oil, and SESAME oil may be
combined. Shortening, like other hydrogenated

vegetable oils, contains
TRANS-FATTY ACIDS as a by-
product of manufacture. The long-term safety of
trans-fatty acids has been questioned. A diet high
in saturated fat is linked to an increased risk of
HEART DISEASE and CANCER. (See also HYDROGENATED
VEGETABLE OIL
; VEGETABLE OIL.)
vegetarian One who eats predominantly VEGETA-
BLES, FRUITS, GRAINS, and NUTS and either limits or
excludes animal products, including
MEAT, FISH,
SEAFOOD, and dairy products from the diet. With a
thoughtful selection of a variety of foods, vegetari-
ans can easily meet all their nutrient needs. People
choose vegetarianism for a variety of reasons.
Vegetarianism may be related to religious or philo-
sophical beliefs. Ecologically, vegetarianism repre-
sents a more efficient use of energy than relying on
meat and meat products. From a health perspec-
tive, plant products do not contain the growth pro-
moters and antibiotics used in poultry and meat
production nor do they contain cholesterol. Plants
are excellent sources of
FIBER and ESSENTIAL FATTY
ACIDS
.
There are varying degrees of vegetarianism:
• Vegans rely on foods of plant origin and omit all
meat, poultry, fish, and eggs, as well as milk and

meat products.
• Fruitarians rely on dry or raw fruits, together
with nuts, honey, grains,
LEGUMES, and OLIVE OIL
while excluding animal products.
• Semivegetarians occasionally eat some meat,
fish, or poultry, eggs and milk or cheese while
relying on cereals, grains, fruit, and vegetables.
644 vegetable shortening
Most “heart healthy” diets are semivegetarian
diets. There are a variety of such diets.
• Ovo-vegetarians include eggs with foods of plant
origin in the diet.
• Lactovegetarians include milk and milk prod-
ucts, together with foods of plant origin.
• Lacto-ovo-vegetarians include both milk prod-
ucts and eggs with grains, fruits, and vegetables.
Vegetarians who eat dairy products tend to have
higher blood cholesterol levels than those who
do not.
• Pescovegetarians include fish and seafood,
together with foods derived from plants.
Vegetarians may have a reduced risk of obesity,
type II (adult onset) diabetes,
GALLSTONES, and
CORONARY ARTERY DISEASE. There is evidence that
vegetarian diets reduce the risk of breast
CANCER,
DIVERTICULOSIS, colonic cancer, hemorrhoids,
OSTEOPOROSIS, and dental caries.

Nutrient Needs
Vegans who are pregnant or lactating, children of
vegans, and people who are ill run the greatest risk
for certain nutrient deficiencies because these indi-
viduals have high nutrient needs that may not be
readily met by eating a limited variety of plant
foods.
Minerals The amounts of many
TRACE MINER-
ALS are low in plant products, and the body’s abil-
ity to absorb them from plant sources is often low.
Milk and milk products provides the most of the
calcium and meat provides the most iron and zinc
in the usual diet. Vegans may have difficulties in
obtaining minerals such as:
•
CALCIUM. Major plant sources are: BROCCOLI,
KALE, COLLARD greens, kelp, PARSLEY, prunes, SE-
SAME seeds, fortified TOFU, and fortified soymilk.
•
ZINC. Sources are: whole grains, BREWER’S YEAST,
LIMA BEANS, SOYBEANS, sunflower seeds, PEAS,
LENTILS, and wheat germ.
•
IRON. This nutrient occurs in dried beans and
peas, dried fruit, fortified cereals, and bread.
Iron uptake can be significantly increased by
eating iron-rich vegetable foods with vitamin C-
rich foods (citrus fruit, berries, dark green leafy
vegetables).

•
COPPER. Copper occurs in AVOCADOS, BARLEY,
BEANS, broccoli, BEETS, PECANS, RAISINS, and soy-
beans.
•
MANGANESE. This nutrient occurs in avocados,
NUTS, seeds, whole grains, legumes, dried peas,
and dark green leafy vegetables.
Energy The energy demands of infants and
growing children are quite relative to their body
size. Fat is a calorie-dense food that is an important
part of a child’s diet. Often vegetarian foods offer
high fiber but low energy (fat) content. When the
diet provides inadequate calories, a muscle protein
is degraded for energy, not a desirable situation in
a young, growing body.
Protein Dietary protein must supply adequate
essential
AMINO ACIDS (the amino acids that cannot
be fabricated in amounts to meet the body’s
requirements). Plant proteins may be less easily
digested depending on the meal preparation. Their
amino acid compositions are usually not as well
balanced as animal protein. Consequently, vegetar-
ian diets based on a single grain like corn can con-
tribute to
MALNUTRITION. Plant proteins from
different sources can complement each other, so
that the net amino acid intake of a mixture of plant
protein can adequately meet the daily requirement

for essential amino acids. For example, combining
whole grain foods with legumes is a traditional
practice (rice and beans, corn and beans, wheat
and lentils, for example).
Vitamin D The best sources of this vitamin are
fatty fish, egg yolk, liver, and milk and milk prod-
ucts—all of which are eliminated from a strictly
vegetarian diet. Exposure to sunlight may meet
individual needs; however, supplementation may
be necessary for people living in northern regions
of the United States during the winter months, as
well as for institutionalized people.
B Vitamins A number of cereal grain products
are enriched with
RIBOFLAVIN, THIAMIN, and NIACIN.
Legumes and whole grains can provide significant
riboflavin.
VITAMIN B
12
deficiency is a major con-
cern for strict vegetarians. There is probably no
very good plant source, other than nutritional
YEAST. The amounts provided in sea vegetables, fer-
mented soy, and algae may be inadequate. The best
sources are animal products such as meat; thus a
vegetarian 645
strict vegetarian may need a supplement, fortified
soy milk, or fortified meat analog. Once vitamin
B
12

deficiency has occurred, the resulting nerve
degeneration may not be reversible.
Strict vegetarian diets are not recommended for
infants or children. Pregnant women should plan
their diet very carefully to maximize nutrient-
dense foods and:
1. emphasize unrefined, whole foods;
2. use protein-rich sources like legumes, seeds,
and nuts;
3. eat a variety of fruits, vegetables, legumes, and
whole grains to assure adequate protein com-
plementation;
4. eat fruit and vitamin C-rich foods with each
meal to enhance iron uptake;
5. consider supplemental sources of vitamin B
12
,
vitamin D, calcium, and trace minerals or prop-
erly fortified sources;
6. eat enough food to provide adequate protein
and energy.
(See also
CHOLESTEROL-LOWERING DRUGS; COM-
PLETE PROTEIN.)
Appleby, P. N. et al. “The Oxford Vegetarian Study: An
Overview,” American Journal of Clinical Nutrition 70,
suppl. (1999): 525S–531S.
Key, T. J. et al. “Health Benefits of a Vegetarian Diet,” Pro-
ceedings of the Nutrition Society 58 (1999): 271–275.
very low-density lipoprotein

(VLDL) A lipid-
protein particle that transports
FAT from the LIVER
to other tissues via the bloodstream. After a carbo-
hydrate meal, the liver absorbs glucose from the
blood and converts it to fat (
TRIGLYCERIDES). The
liver packages fat to export it to other parts of the
body via the bloodstream in the form of VLDL. In
composition, VLDL resembles chylomicrons, the
fat transport vesicles from the intestine. VLDL
contains triglycerides, a low amount of
CHOLES-
TEROL, and two types of protein designated B-100
and C-II.
When VLDL reaches the capillaries, its triglyc-
erides are broken down by an enzyme in the walls
of the capillaries called lipoprotein lipase. Tissues
then absorb the released fatty acids. After releasing
their fat, VLDL remnants follow an unusual path-
way: They become enriched in cholesterol as they
are transformed in the blood to
LOW-DENSITY
LIPOPROTEIN
(LDL)—the particle that carries choles-
terol to tissues.
The blood levels of both chylomicrons and VLDL
increase for several hours after eating. Therefore,
lab tests that measure triglycerides in serum, the
clear cell-free fluid remaining after blood clots, are

usually performed after an overnight fast when
levels have stabilized. Middle-aged white males
with high levels of serum triglycerides (essentially
VLDL) and high LDL appear to be more likely to
have heart attacks than men with normal levels,
even in the people with somewhat elevated serum
cholesterol levels. The risk of heart attack may
decrease by lowering serum triglycerides and rais-
ing
HIGH-DENSITY LIPOPROTEIN (HDL), the “desirable
cholesterol.” (See also
CARDIOVASCULAR DISEASE; FAT
METABOLISM
.)
villi Microscopic, fuzzy layer coating the inner
side of the wall of the
SMALL INTESTINE like a shag
carpet. Cells that line the surface of villi possess
numerous, tiny projections called
MICROVILLI.If all
of the intestinal folds, villi, and microvilli were flat-
tened out, the total surface area would be about
the size of a tennis court. Thus villi dramatically
increase the absorptive area of the intestinal sur-
face and facilitate efficient nutrient uptake.
CELIAC
DISEASE
, CROHN’S DISEASE, and intestinal parasitic
diseases (like
GIARDIASIS) can lead to a loss of the

villi and subsequent
MALABSORPTION and maldiges-
tion syndromes. With appropriate treatment and
dietary modification, the villi can grow back and
digestion can improve. (See also
DIGESTION; DIGES-
TIVE TRACK.)
villikinin A hormone produced by the SMALL
INTESTINE
that stimulates the movement of VILLI,
microscopic hair-like projections that coat the
inner surface of the small intestine. This action
serves to mix chewed food and digestive juice
(
CHYME) and to increase nutrient absorption by the
intestine. (See also
DIGESTION; ENDOCRINE SYSTEM.)
vinegar A dilute solution of ACETIC ACID. The
term is derived from the French vinaigre, which
646 very low-density lipoprotein
means sour wine. Vinegar has been used in food
preservation and medicine for thousands of years.
Typically vinegar contains 4 percent to 12 percent
acetic
ACID, which is produced by the bacterial
oxidation of alcohol formed by the fermentation of
sugars and fruits. Apples yield cider vinegar;
grapes, wine vinegar; and sugar and hydrolyzed
starches from corn and wheat, white vinegar.
Depending upon the nature of the fruit fermented,

the resulting vinegar will have a unique flavor
without adding significant calories. Vinegar pro-
vides only two calories per teaspoon. Because it
is so acidic, vinegar is used to preserve foods in
pickling. In salad dressing,
MAYONNAISE, MUSTARD
,
and tomato sauce, vinegar helps retard spoil-
age. Vinegar contains traces of minerals but it is
not a significant food source. (See also
FOOD PRO-
CESSING.)
vitamin An essential organic nutrient. Minute
amounts of vitamins participate in three general
functions of the body: growth, protection, and
energy regulation. There are a total of 13 vitamins.
Four are fat-soluble vitamins A, D, E, and K. The
rest are water-soluble. Eight vitamins are in the B
complex:
RIBOFLAVIN (B
1
),
THIAMIN (B
2
),
NIACIN
(B
3
), VITAMIN B
6

, vitamin B
12
, FOLIC ACID
, PAN-
TOTHENIC ACID, and biotin. VITAMIN C is also water-
soluble but is not considered a B vitamin, which
function as enzyme helpers (coenzymes).
Vitamins either cannot be synthesized by the
body or they cannot be made in adequate amounts,
so they must be supplied by the diet. As examples
of the latter, vitamin D can be made in the skin
when exposed to sunlight, while some niacin can
be made from the amino acid tryptophan. The
intestine is a source of
BIOTIN, pantothenic acid, and
VITAMIN K; these are supplied by “friendly” intesti-
nal bacteria, though the exact amounts supplied
are difficult to assess.
The term vitamin dates from 1912, and the first
vitamin to be isolated was vitamin A in 1913. Thi-
amin was discovered in 1926, vitamin K in 1929,
and vitamin C in 1932. Vitamin B
12
was the most
recent vitamin to be discovered (1948). Before a
compound can be classified as a vitamin, it must be
proven that animals must obtain the compound
from their diet. Typically, scientists test lab animals
such as mice with a diet free of the test substance,
together with a dose of antibiotics to eliminate

intestinal bacteria.
Vitamins originate chiefly from plant sources.
Except for vitamin D and vitamin C, vitamins are
present in animal tissue only if the animal con-
sumes foods containing them or harbors microor-
ganisms capable of synthesizing them. B vitamins
are universally distributed; fat-soluble vitamins
may be absent from some types of organisms. Each
of the vitamins plays a specific role in the body; a
deficiency of one vitamin cannot be eliminated by
consuming an excess of another.
Fat-Soluble Vitamins
VITAMIN A, VITAMIN D, VITAMIN E, and vitamin K are
oily materials and dissolve in fats and oils, not in
water. Unlike the B complex, these vitamins gener-
ally do not serve as enzyme helpers, nor are they
involved in energy production; each has an
entirely different function, ranging from acting as
an
ANTIOXIDANT (E), to producing a visual pigment
for night vision (A), to blood clothing (K), and to
bone formation (D).
Fat-soluble vitamins are absorbed best when
they are eaten with fats and oils. These vitamins
are stored in the body, so they do not need to be
consumed daily. Because they are stored, excessive
consumption can lead to high tissue levels resulting
in toxic side effects, especially for vitamins A and
D. For example, 50,000 international units of vita-
min A over several months can cause toxic symp-

toms in adults. Symptoms of toxicity, such as achy
joints, fatigue, headaches, and nausea, disappear
when the high intake stops. What represents an
excessive intake depends on many factors, includ-
ing the type of vitamin, individual tolerance, which
varies with age, and the length of time for which
the supplement is taken.
Water-Soluble Vitamins
B complex vitamins help convert food into energy;
they include
THIAMIN (B
1
), RIBOFLAVIN (B
2
), NIACIN
(B
3
), VITAMIN B
6
, pantothenic acid, and biotin.
FOLIC ACID and vitamin B
12
are involved in build-
ing new cells, while vitamin C serves as an antiox-
idant and helps build healthy capillaries, gums, and
joints. Except for vitamin B
12
, water-soluble vita-
mins are not stored well in the body and must be
vitamin 647

replenished daily. Excesses are generally excreted
in the urine.
Vitamin Deficiencies
Long-term vitamin deficiencies often lead to seri-
ous illness. Deficiencies can be due to an inade-
quate diet (
MALNUTRITION); inability to digest food
(maldigestion); inability to absorb vitamins due to
damage to the intestine or to competition with
another material such as a drug (
MALABSORPTION);
increased physiological need as during pregnancy;
growth, injury, choice of lifestyle, or other envi-
ronmental factors.
Physicians may use lab tests to diagnose vitamin
deficiencies. Most tests involve blood analyses,
even though these are not always reliable. For
example, a common antibody test for serum vita-
min B
12
detects both vitamin B
12
together with
inactive derivatives. Measurement of enzyme lev-
els or levels of metabolic products can provide use-
ful information. Dietary analysis can reveal levels
of nutrients in the diet and guide a nutritional eval-
uation and assessment of individual needs comple-
menting the physical examination and health
history.

Natural vs. Synthetic Vitamins
Natural vitamins are those occurring in food. All
substances classified as vitamins have been isolated
from animal or plant sources, and most have been
chemically synthesized in the lab to establish their
structures. In other words, synthetic vitamins are
usually identical to the product in cells. As an exam-
ple, vitamin C in cells is defined chemically as L-
ascorbic acid, identical to synthetic L-ascorbic acid.
Most vitamins found in supplements are chemically
synthesized, because there simply is not enough of
most vitamins extracted from plant materials to
meet world demand. Most vitamin C comes from a
few major commercial sources worldwide.
A few synthetic vitamins differ from the natural
forms. Synthetic vitamin E, called d, 1-alpha-
tocopherol, is a mixture of both left- and right-
handed molecules, while the natural alpha toco-
pherol is a single form called d-tocopherol. The
synthetic product is adjusted to provide the same
biological activity as the natural form. Certain vita-
mins like vitamin B
12
possess structures that are
too complex for a convenient lab synthesis. Micro-
bial sources have been selected to produce large
amounts.
Vitamin Supplements
Nutritionists often recommend obtaining vitamins
from foods for several reasons.

Foods supply mixtures of vitamins, minerals,
and other materials that may have beneficial
effects. Mixtures are what the body uses. Foods
supply materials that are not vitamins, yet are
important. In this class are
FLAVONOIDS, which work
together with vitamin C to build strong capillaries
and serve as antioxidants and as anti-inflammatory
agents. Substances with anticancer properties have
recently been isolated from vegetables of the cab-
bage family; they include isothiocyanates and
indoles, in addition to the flavonoids.
Recent surveys show that about 158 million
consumers take supplements and spend about $8.5
billion yearly on vitamins, minerals, and other sup-
plements. One explanation for this widespread
practice is that many people have subclinical defi-
ciencies. They are not sick, but they are not well,
either. They may want to feel more energetic and
to have more stable moods. Others want to take
supplements as insurance in preventing certain dis-
eases if they live in a polluted environment or if
their genetic makeup, medical history, and lifestyle
choices warrant it. A growing number of con-
sumers want to promote optimal health. Although
there is a natural tendency to search for an easy
solution to health problems, there are limits
regarding what vitamins can do for health. No sin-
gle supplement can compensate for overindul-
gence, physical inactivity, or genetic predisposition.

Deciding who needs vitamin supplements and
how much should be taken is a controversial area.
Conventional wisdom says that by following
DIETARY GUIDELINES FOR AMERICANS and using a rec-
ommended plan such as the
FOOD PYRAMID, an indi-
vidual should be assured of an adequate supply of
nutrients. Thus, if an individual is healthy and is
eating a
BALANCED DIET, vitamin supplements
would not be needed. There is general agreement
that individuals with well recognized needs may
require supplements. These people include:
• women with heavy menstrual bleeding (extra
IRON)
648 vitamin
• women taking oral contraceptives (may need
extra vitamin B
6
)
• pregnant women (extra iron, folic acid, and
CAL-
CIUM
)
• malnourished individuals, including dieters,
elderly people with a low caloric intake, chronic
alcoholics, and those with other chemical
dependencies
• strict vegetarians (many need extra iron, zinc,
calcium, and vitamin B

12
)
• newborn infants (may be deficient in vitamin E
and vitamin K)
• individuals with chronic disorders, such as
patients with
OSTEOPOROSIS (may need extra
vitamin D, calcium, magnesium, and trace
minerals)
• hospitalized patients. Patients in hospitals and
institutionalized people may become deficient in
one or more vitamin.
• people who smoke (extra vitamin C)
Another viewpoint is that many people who live
in modern industrial societies and are exposed to
environmental stressors and rely on refined foods,
often can benefit from supplements for optimal
health and maximal longevity. However, the opti-
mal amounts for any vitamin are merely estimates.
Other individuals may benefit from supplements
when their nutrient consumption is below normal
although they lack symptoms of serious deficiency
diseases. It has been proposed that nutrient needs
increase with:
• exposure to pollution
• physical and mental stress
• frequent skipping of meals
• increased reliance on highly processed foods
• inadequate exercise and rest
• use of recreational drugs and alcohol

• widespread chemical and food sensitivities
• increased prevalence of conditions characterized
by suppressed immunity, including
AIDS
• dieting
There are many advantages in obtaining nutri-
ents from food: It is practically impossible to get an
overdose. Food supplies mixtures of nutrients and
mixtures are what the body needs; food supplies
other substances that may have beneficial effects
and are not found in a pill or capsule. But supple-
ments can be used as part of a wellness program to
prevent illness and promote well-being. Such a
program should include physical exercise, eating
wholesome meals, maintaining psychological fit-
ness and emotional stability.
Any patient who is considering taking dietary
supplements should:
• Consult with a knowledgeable health profes-
sional about possible contraindications, adverse
side effects, or interference with other medica-
tions or treatments the patient is receiving.
• Avoid taking any supplements while pregnant
or nursing unless under the advice or supervi-
sion of a doctor.
• Focus on individual needs—more does not nec-
essarily mean better.
• Tell their doctors what supplements they are
taking, especially before submitting to a blood or
urine test, as the results can be affected by some

supplements.
• Be aware of sensitivities to wheat, soy, yeast,
corn, milk, artificial coloring, starch, or preserv-
atives—many supplements contain these prod-
ucts.
• Select supplements with multiple nutrients—
many nutrients work best in tandem with others.
• Test supplements for their ability to dissolve (a
sign that they will be effective) by placing them
in a cup of warm water with a teaspoon of vine-
gar to see if they disintegrate within 45 minutes.
• Keep vitamins and minerals out of children’s
reach.
• Monitor the effect of the supplement to ensure
it is providing a health benefit.
(See also
ORTHOMOLECULAR MEDICINE; SUBCLINI-
CAL NUTRIENT DEFICIENCY.)
Hathcock, J. N. “Vitamins and Minerals: Efficacy and
Safety,” American Journal of Clinical Nutrition 66, no. 2
(1997): 427–437.
vitamin A (retinol) A fat-soluble vitamin and
one of the first vitamins to be discovered. Vitamin
A is required for a healthy immune system, vision,
vitamin A 649
growth, and reproduction. Vitamin A supports nor-
mal tissue development, which accounts for its
influence on taste and hearing. The liver stores 90
percent or more of this vitamin. Many plants pro-
duce a parent compound of vitamin A called

BETA-
CAROTENE
, also called “provitamin A.” This
orange-yellow pigment is stored in fat tissue and
other tissues, but comparatively little is stored in
the liver, unlike vitamin A. Beta-carotene is
cleaved to form retinol and an inactive molecule
called retinoic acid, which lacks vitamin A activity.
Vitamin A and Vision Perhaps the best known
role for vitamin A is its effect on vision. Vitamin A
forms a pigment in the eye called visual purple,
required for night vision, and outright deficiency
causes
NIGHT BLINDNESS. Large amounts of vitamin
A taken daily can delay blindness caused by retini-
tis pigmentosa, an inherited disease that leads to
degeneration of the retina. It is worth noting that
vitamin A has no effect on defective vision from
other causes, and most vision problems do not
involve vitamin A.
Wound Healing Both vitamin A and beta-
carotene speed wound healing in lab animals. The
effect is quite pronounced when the animals are
vitamin-A deficient.
Resistance to Infection Population studies in
developing nations have demonstrated that vitamin
A reduces death by increasing resistance to infec-
tions, such as measles. This is not surprising because
vitamin A supports a healthy
IMMUNE SYSTEM,

including increased production of antibodies and
various lymphocytes (disease-fighting cells). Beta-
carotene, which is nontoxic, increases T-helper cells
even in normal people. Lowered immunity due to
surgery has been blocked in patients given large
amounts of vitamin A, and it increases the resistance
of the digestive system and the respiratory tract to
infection. Vitamin A can minimize decreased immu-
nity due to radiation and chemotherapy.
Cancer Vitamin A and beta-carotene possess
anticancer properties. Vitamin A can block cancer
cells in cultures, and even block malignancy in ani-
mals exposed to cancer-causing agents (
CARCINO-
GENS). A diet rich in beta-carotene and other
carotenoids may lower the risk of lung, bladder,
larynx, esophagus, stomach, prostate, and colon
cancer.
Vitamin A, a product of vitamin A called
retinoic acid, and beta-carotene may be able to
prevent or eliminate precancerous sores (leuko-
plakia) in the mouths of smokers. Retinoic acid
may also prevent recurring tumors of the head and
neck. Another derivative of vitamin A, tretinoin
(retin A), may be able to combat precancerous cer-
vical conditions.
Skin Conditions Vitamin A can clear up
ACNE
but extremely large doses are required to do so,
increasing the risk of toxicity. Derivatives are

more effective; for example, tretinoin clears up
the most common form of acne, acne vulgaris,
and another derivative (etretinate) may be useful
for psoriasis. Tretinoin helps with sun-damaged
skin, although long-term effects on aging skin are
not clear.
Other Conditions Vitamin A supports the
maintenance and healing of lung tissue and the
intestine, and it has been used to treat peptic ulcers
and inflammatory bowel disease. Vitamin A defi-
ciency associated with AIDS is linked to decreased
T-helper lymphocytes and a higher rate of mortal-
ity due to HIV. Because retinoic acid may increase
HIV replication, beta-carotene could be the pre-
ferred form for supplementation.
Sources
Vitamin A is either supplied as such in food, or it is
formed from beta-carotene in the body. Fish liver
oil and liver are rich in vitamin A. Milk is fortified
with vitamin A. Vitamin A palmitate is often the
form of the vitamin found in supplements. Its
advantage is that it is easily suspended in water,
therefore it is easily absorbed by the body. Beta-
carotene occurs in yams, winter
SQUASH, carrots,
and
CANTALOUPE, as well as in dark green leafy veg-
etables like
KALE and SPINACH.
Requirements

The amount of vitamin A in a food can be given in
terms of retinol equivalents (RE). One RE is
defined as 1 mcg of retinol or 6 mcg of beta-
carotene. The uptake of beta-carotene is less than
retinol and its conversion to retinol is incomplete.
Vitamin A activity may also be expressed in inter-
national units (IU). One IU of vitamin A activity
equals 0.3 mcg of retinol or 0.6 mcg of beta-
carotene. Put another way, 1 retinol equivalent
650 vitamin A
equals 3.33 IU of retinol (preformed vitamin A
from animal sources) or 10 IU of beta-carotene
(plant sources).
The
RECOMMENDED DIETARY ALLOWANCE (RDA)
for vitamin A for men (25 to 50 years) is 1,000 mcg
of retinol or retinol equivalents and 800 mcg (RE)
for nonpregnant women. In pregnancy, the
requirement increases to 1,300 mcg. Vitamin A
deficiency is common in nonindustrialized soci-
eties, but a significant number of Americans might
also be deficient in vitamin A, particularly young
children and others consuming highly processed
foods. Factors that increase the need for vitamin A
include a high-fiber diet, chronic fat
MALABSORP-
TION, stress, and high alcohol consumption. Symp-
toms of deficiency include coarse dry skin, slow
growth, night blindness, frequent infections, and
anemia.

Safety
Women who are pregnant should not take vitamin
A supplements. Amounts greater than 10,000 IU
(3,000 RE) increase the risk of birth defects. On the
other hand, there is no evidence that beta-carotene
produces birth defects. Vitamin A is stored by the
body and it is possible to accumulate too much,
leading to toxicity (
HYPERVITAMINOSIS
). The re-
sponse to high doses of vitamin A is quite variable.
A high intake of 50,000 IU daily (15,000 RE) may
be tolerated by some; others may have a reaction
with 20,000 IU (6,000 RE). Symptoms of vitamin A
overdose include headache, fatigue, dry skin,
weakness, nausea, hair loss, blurred vision, bone
aches, and loss of appetite. Jaundice and liver dam-
age are possible. These symptoms usually disappear
rapidly when vitamin A supplementation is
stopped. In contrast, beta-carotene is relatively safe
because it is converted to vitamin A only as
needed.
Tretinoin, accutane, and etretinate should not
be taken by pregnant women or by women who do
not use birth control because of the high risk of
BIRTH DEFECTS. Vitamin A may cause bone disease
in individuals with chronic kidney problems.
Bates, C. J. “Vitamin A,” Lancet 345 (January 7, 1995):
31–35.
vitamin B

1
See THIAMIN.
vitamin B
2
See RIBOFLAVIN.
vitamin B
3
See
NIACIN.
vitamin B
6
(pyridoxine) An essential water-solu-
ble nutrient and a member of the
B COMPLEX. The
term “vitamin B
6
” pertains to two forms, pyridox-
ine and pyridoxamine, which can be converted
back and forth. Vitamin B
6
is required by the body
to produce nonessential
AMINO ACIDS, to break
down most amino acids, and to support healthy
immune systems, normal immunity, and nerve
function. However, before it can help enzymes, vit-
amin B
6
like other B complex vitamins must be
activated. The enzyme helper (

COENZYME) in this
case is pyridoxal phosphate, employed by a family
of enzymes called transaminases required in the
first stage of amino acid utilization by the body.
Chemicals known as hydrazides and hydrazines
interfere with the functions of vitamin B
6
. These
chemicals are widely used in industry and conta-
minate the food supply. Derivatives of hydrazines
appear in cigarette smoke and food additives, thus,
the environmental burden could deplete this
nutrient.
Possible Roles in Maintaining Health
Red Blood Cells Vitamin B
6
is essential for the
production of
RED BLOOD CELLS. Vitamin B
6
plays a
role in protein synthesis as well as in the synthesis of
DNA and RNA, and it is required to make HEME, the
red pigment of the oxygen transport protein of blood
(
HEMOGLOBIN). A deficiency can cause anemia.
Nervous System The formation of certain brain
chemicals (
NEUROTRANSMITTERS) from amino acids
requires this vitamin, hence it affects the

NERVOUS
SYSTEM
. Certain inherited metabolic disorders lead
to convulsions in infants, and B
6
supplementation
usually abolishes their seizures.
Immune System Vitamin B
6
is one of the most
important B vitamins in maintaining a robust
IMMUNE SYSTEM. Vitamin B
6
supplements can boost
immunity in older people who may not consume
enough of this important vitamin. Vitamin B
6
defi-
ciency decreases immune function in humans and
lab animals, and low vitamin B
6
levels are com-
mon in people with weakened immunity, includ-
ing people with
CANCER and AIDS. Vitamin B
6
also
vitamin B
6
651

protects against certain types of cancer in lab
animals.
Premenstrual Syndrome (PMS) Vitamin B
6
has
long been claimed to relieve an array of symptoms
occurring in the week to 10 days prior to menstru-
ation. PMS affects the synthesis of several hor-
mones believed to be involved in the cycle. Vitamin
B
6
has been used to correct for some of the imbal-
ances caused by estrogen-type birth control pills.
Some clinical studies suggest that vitamin B
6
can
improve certain symptoms of PMS, such as breast
tenderness and PMS-related depression. Lower
doses, 50–100mg/day are apparently as effective as
large amounts.
Carpal Tunnel Syndrome Vitamin B
6
supple-
mentation is apparently ineffective in providing
short-term relief of symptoms, based on evaluation
of randomized, controlled clinical trials.
High Blood Sugar Vitamin B
6
has been
used to help treat diabetic patients whose condi-

tion can be attributed in part to a deficiency of this
vitamin.
Cardiovascular Disease Vitamin B
6
may
decrease the stickiness of platelets, cell fragments
in the blood needed for clot formation, and thus
the tendency to form blood clots. A deficiency of
this vitamin has been linked to
ATHEROSCLEROSIS
in some instances, due to an accumulation of
excessive amounts of an amino acid breakdown
product homocysteine. Vitamin B
6
combined with
folic acid and vitamin B
12
can reduce blood levels
of homocysteine, a potential risk factor for cardio-
vascular disease. It is uncertain whether reducing
homocysteine prevents death from heart disease,
however.
Senility Vitamin B
6
deficiency is linked to
long-term memory loss in some elderly patients.
Other Conditions Some forms of arthritis and
joint pain respond to extra vitamin B
6
. In combi-

nation with magnesium this vitamin can lower the
risk of calcium oxalate kidney stones, the most
common kind. Vitamin B
6
deficiency is common
among patients with asthma.
Sources
Vitamin B
6
occurs in FISH; MEAT, including liver and
kidneys;
BLACKSTRAP MOLASSES; NUTS and whole
GRAINS; BREWER’S YEAST; and many VEGETABLES.
Requirements
The Recommended Dietary Allowances (RDA) for
adults (25 to 50 years) is 2.0 mg for men and 1.6
mg for women. Many people do not obtain ade-
quate amounts of this vitamin and it is one of the
most common deficiencies. Those most at risk are
older persons; it has been found that 61- to 71-
year-olds need more vitamin B
6
than the RDA.
Others who may not consume enough vitamin B
6
include adolescent women and pregnant and lac-
tating women, alcoholics, and those with other
chemical dependencies.
Factors that may increase the need for vitamin B
6

include alcohol consumption, several medications
(L-dopa, penicillamine, hydralazine isoniazid),
smoking, a high protein diet, deficiencies of magne-
sium,
ZINC,and RIBOFLAVIN. A mild deficiency is
sometimes associated with lowered immunity and
nervous disorders. Severe deficiency causes depres-
sion, confusion, convulsions, inflamed mouth, and
tongue, and skin disorders. The optimal amount for
maximal health and longevity is not known.
Safety
There is general agreement that amounts up to 50
mg per day are relatively safe. Higher levels should
be taken only with professional advice. Excessive
consumption of vitamin B
6
can damage the ner-
vous system and lead to numbness of hands and
feet (peripheral neuropathy). Insomnia and anxi-
ety are possible symptoms of excessive intake. Vit-
amin B
6
reduces the effectiveness of levodopa, a
drug used to treat
PARKINSON’S DISEASE. (See also
AMINO ACID METABOLISM; DIABETES MELLITUS;
TRANSAMINATION.)
Siri, P. W. “Vitamins B
6
, B

12
, and Folate: Association
with Plasma Total Homocysteine and Risk of Coronary
Atherosclerosis,” Journal of the American College of
Nutrition 17 (1998): 435–441.
vitamin B
12
(cyanocobalamin) An essential
water-soluble nutrient belonging to the
B COMPLEX
that is required in extremely minute amounts for
cell division and growth. Vitamin B
12
is unique in
several respects: It is the only B vitamin stored in
the body and the only known nutrient to contain
the trace mineral
COBALT. Like all B vitamins, vita-
652 vitamin B
12
min B
12
must be chemically modified to form a
coenzyme (enzyme helper) before it can participate
in metabolism. Vitamin B
12
has important, though
very limited, roles in metabolism. It assists in the
utilization of single carbon (methyl) groups trans-
fer from the amino acid, methionine, to donors,

including thymin, a building block for DNA. Vita-
min B
12
also helps to oxidize certain fatty acids and
it supports the maintenance of healthy nerves.
With deficiencies, irreversible brain damage and
nervous disorders can occur.
The body has evolved an efficient mechanism to
absorb this vitamin. To begin the process, the stom-
ach normally secretes
INTRINSIC FACTOR
, a protein
that binds vitamin B
12
and carries it to the INTES-
TINE where it aids B
12
absorption. An estimated 20
percent of people in their 60s and 40 percent of
people in their 80s develop atrophic gastritis, in
which the stomach does not produce enough acid
and intrinsic factor. With inadequate stomach acid
to sterilize the stomach, certain bacteria can grow,
consuming the vitamin that otherwise would be
absorbed by the intestine. Vitamin B
12
, together
with another B vitamin,
FOLIC ACID, functions in
DNA

synthesis and cell division, and supports red
blood cell production. A large dose of folic acid to
treat anemia can mask a vitamin B
12
deficiency;
folic acid often is administered with B
12
.
Possible Roles in Maintaining Health
Anemia A deficiency of intrinsic factor causes
PERNICIOUS ANEMIA
, a disease caused by inadequate
B
12
absorption despite adequate dietary supplies.
B
12
injections clear up the problem.
Vitamin B
12
Deficiency Signs of B
12
deficiency
include weakness in arms and legs, walking prob-
lems and paralysis, and irreversible nerve damage.
Prolonged deficiency causes anemia and neurolog-
ical symptoms. Vitamin B
12
deficiency is particu-
larly a concern for strict vegetarians; older adults;

pregnant women; patients with bleeding, cancer,
kidney or liver disease; alcoholics; patients with
malabsorption syndromes, such as Crohn’s disease;
people with severe food sensitivities; those with a
family history of anemia, or who have undergone
stomach surgery.
Nervous Disorders An estimated 10 percent of
elderly persons have marked vitamin B
12
deficien-
cies, and many patients with senile dementia are
B
12
-deficient. Mental deterioration, SENILITY, and
neuropsychiatric disorders—including dementia,
DEPRESSION
, and loss of balance—may respond to
extra vitamin B
12
. About 5 percent of adults over
the age of 50 have low vitamin B
12
levels. Half of
these may have difficulty in absorbing the vitamin
from food.
Cigarette Smoking Smokers have low vitamin
B
12
and folic acid levels. Preliminary clinical stud-
ies suggest that supplementation with both vita-

mins may reduce the amount of precancerous
bronchial tissue.
Chronic Pain Vitamin B
12
has been used to
treat bronchial spasm (
ASTHMA), bursitis, and bone
spur pain. Neuralgia pain radiating along nerves
may respond to intramuscular infections of vitamin
B
12
.
Sources
Vitamin B
12
occurs mainly in animal products—
MEAT, POULTRY, FISH, EGGS, and SHELLFISH. Some for-
tified foods like nutritional yeast contain vitamin
B
12
. Tamari, tempeh, and miso were found to be
essentially lacking in this vitamin, although some-
times these foods are claimed to be rich sources of
the vitamin.
SPIRULINA contains fewer usable vita-
mins than formerly believed; the amount in sea-
weed is variable. Part of the problem seems to be
that seaweed contains B
12
analogs that do not form

coenzymes in the body. Therefore, strict vegetarians
(those who eat no animal products) may need to
support their diet with vitamin B
12
supplements.
Requirements
The
RECOMMENDED DIETARY ALLOWANCE (RDA) for
vitamin B
12
for normal adults is 2 mcg daily.
Severe vitamin B
12
deficiency is rare. Newer, more
sensitive laboratory blood tests and metabolic indi-
cators have turned up low-level B
12
deficiencies
with surprising frequency. Low folic acid intake
and some antibiotics interfere with Vitamin B
12
uptake. People suffering from anxiety or depres-
sion who take antidepressants (tricyclics and chlo-
romazine) may block vitamin B
12
uptake.
Vitamin B
12
is not toxic when taken orally.
Nasal or sublingual (under the tongue) vitamin B

12
gels or vitamin injections are effective for vegetari-
vitamin B
12
653
ans and for those with malabsorption problems.
There is no known toxicity associated with this vit-
amin when taken orally. Often, elevated vitamin
B
12
in the blood is most readily obtained through
B
12
injections. Some people are allergic to injec-
tions. (See also
ACHLORHYDRIA; AGING; DIGESTION
;
MALABSORPTION
.)
Naurath, Hans J. et al. “Effects of Vitamin B
12
, Folate and
Vitamin B
6
Supplements in Elderly People with Nor-
mal Serum Vitamin Concentrations,” Lancet 346 (July
8, 1995): 85–89.
vitamin C
(ascorbic acid, sodium ascorbate, cal-
cium ascorbate) A water-soluble vitamin that

promotes wound healing and healthy blood ves-
sels, joints, gums, and connective tissue. Vitamin C
helps in the synthesis of
COLLAGEN, a structural pro-
tein that provides strength to bones and tissues.
Most animals make ample vitamin C; exceptions
include guinea pigs, humans and other primates,
and certain bats.
Vitamin C occurs in high levels in endocrine
(hormone-secreting) glands. It is needed by the
ADRENAL GLANDS to make hormones: EPINEPHRINE
(adrenaline), a stress hormone, plus the steroids
regulating
BLOOD SUGAR and the hormones regulat-
ing blood minerals, and assists in the activation of
other hormones. Vitamin C also occurs in high lev-
els in the brain, and it plays a role in nerve trans-
mission through the production of
SEROTONIN and
norepinephrine, brain chemicals called
NEURO-
TRANSMITTERS. Neurotransmitters are chemicals
synthesized by nerve cells to conduct impulses
between cells. Vitamin C is involved in the metab-
olism of folic acid.
Vitamin C serves as a powerful antioxidant and
helps to prevent oxidative damage in the body. It
can block many types of highly reactive chemical
species called
FREE RADICALS, including superoxide

and hydroxyl radicals in blood and body fluids, as
well as regenerating
VITAMIN E, the free radical
scavenger of cell membranes and lipids. As a versa-
tile antioxidant, vitamin C offers protection against
airborne pollutants and supports drug detoxication
by the liver. Dietary vitamin C can increase the
absorption of heme iron (the form in meat) two- to
fourfold. Vitamin C suppresses the formation of
NITROSOAMINES and quinones, known to cause can-
cer (carcinogens). On the other hand, it is possible
that vitamin C can participate in the BHA-induced
tissue growth in the stomach of rats, thus enhanc-
ing carcinogenesis. However, a higher consump-
tion of vitamin C contributes to higher plasma
levels of other antioxidants, including vitamin E.
Possible Role of Vitamin C in Disease
The functions of vitamin C in the body and the
amounts required for optimal health remain one of
the most controversial areas in nutrition. The fol-
lowing topics have been the focus of recent
research.
Scurvy This full-blown vitamin C deficiency
disease is characterized by swollen joints, poor
wound healing, muscle wasting, bleeding gums
and susceptibility to infection. In scurvy, defective
COLLAGEN is formed, leading to diseased connective
tissue. Vitamin C is required to synthesize collagen
building blocks, hydroxylysine and hydroxypro-
line, for normal collagen formation. Scurvy has

largely been eradicated from industrialized nations,
though it continues to affect certain populations:
the elderly, alcoholics, and chronically ill people.
When large amounts of vitamin C are consumed,
the body adapts by accelerating excretion and
metabolism. When consumption suddenly drops, a
person may experience a short-term vitamin C
deficiency until the body readapts (“rebound
scurvy”). Infants born to mothers who have taken
large amounts of vitamin C may experience
rebound scurvy after birth unless they are supple-
mented.
Infection and Colds Whether vitamin C can
cure the common cold has remained a controver-
sial issue since Dr. Linus Pauling first suggested it in
1970. The research that has been conducted since
that time has yielded mixed results, possibly
reflecting flaws in experiment design. There is gen-
eral agreement that vitamin C can decrease the
duration and severity of colds. The vitamin can
affect the outcome by blocking viruses, as well as
by helping the
IMMUNE SYSTEM. White cells that
devour bacteria and abnormal cells require vitamin
C for normal functioning; vitamin C levels decline
in these cells during infection and exposure to
drugs, medications, alcohol, and cigarette smoking.
Cancer A variety of population studies suggest
that a low vitamin C intake correlates with a higher
654 vitamin C

rate of CANCER and that vitamin C from dietary
sources has a protective effect for cancer of the oral
cavity, larynx, esophagus, colon, lung, and stom-
ach. Data supporting a beneficial relationship
between vitamin C and bladder, cervix, endo-
metrium, and breast cancer are not as convincing,
although suggestive. Vitamin C supplementation
reduces the rate of precancerous changes in the
stomach. It protects against cervical dysplasia, a
predisposing condition to cervical cancer, and it
inhibits human leukemia cells in culture. Vitamin
C can block the formation of cancer-causing agents
like
NITROSOAMINES, and it is a powerful blocker of
free radicals, which can be carcinogenic. Whether
vitamin C does more than prevent certain cancers,
and whether it can extend the lives of terminally ill
cancer patients, remains controversial. More
research is needed to resolve these issues.
Cardiovascular Disease A popular hypothesis
for the origin of atherosclerosis (cholesterol
clogged arteries) states that the oxidation of LDL
promotes the disease process. Vitamin C may help
prevent oxidative damage to
LOW-DENSITY LIPOPRO-
TEIN (LDL), lipid-transport particles implicated in
clogging arteries. Vitamin C can increase
HIGH-
DENSITY LIPOPROTEIN (HDL), the beneficial form of
cholesterol, and it may lower total cholesterol val-

ues. However, epidemiologic studies did not detect
a correlation between vitamin C intake and the
risk of cardiovascular disease, and there as yet
have not been randomized clinical studies of
vitamin C supplements in reducing cardiovascular
risk.
The Physicians Health Study found that taking
vitamin C or multivitamins was not associated
with a significant decrease in death rates from car-
diovascular disease. The study included 83,639
male physicians in the United States who had no
history of heart disease at baseline and were fol-
lowed for an average of 5.5 years. Population stud-
ies have found an increased risk of elevated blood
pressure with low vitamin C intake or low vitamin
C plasma levels. Vitamin C together with usual
antihypertensive drugs may decrease high blood
pressure. Increased consumption of foods rich in
vitamin C may decrease the risk of stroke. In com-
bination with vitamin E, vitamin C may also slow
the progression of atherosclerosis in men. Studies
of treatment of hypertension with vitamin C have
not been conclusive. Mortality from all causes of
death was strongly inversely related to vitamin C
intake, but other studies of vitamin C in prevent-
ing cardiovascular disease have yielded negative
results.
Aging Free radical damage is implicated in
aging, which can be viewed as the result of accu-
mulated damaged protein and DNA and of dam-

aged repair mechanisms. Population studies
suggest that the consumption of ample fruits and
vegetables, including those that are rich sources of
vitamin C, decrease the risks of degenerative dis-
eases associated with aging. Of the multitude of
beneficial substances in these foods with antioxi-
dant activity, vitamin C appears likely to play a cen-
tral role.
Allergies Vitamin C can help reduce asthma in
certain asthmatics, and it may reduce the severity
of allergy symptoms by alleviating stuffy sinuses,
achy joints and puffy eyes. Vitamin C helps detox-
ify
HISTAMINE
, which promotes these inflammation
symptoms.
Eye Disease Free radicals probably promote
cataracts and macular degeneration with aging.
Thus, animals fed vitamin E-deficient diets develop
macular degeneration and people with low-levels
of antioxidants in their blood have a higher risk of
cataracts. Adequate vitamin C, carotenoids, and
vitamin E consumption are related to a decreased
risk of cataracts associated with aging. Several stud-
ies have suggested that antioxidant supplements,
including vitamin C, decrease the risk of cataract
formation. Vitamin C supplementation may halt or
retard cataract development. Together with zinc
and other antioxidants vitamin C may slow the
progression of intermediate and advanced stages of

age-related macular degeneration according to a
clinical trial.
Other Conditions A variety of studies suggest
that supplements of vitamin C can: decrease the
risk of
PERIODONTAL DISEASE, help diabetics main-
tain healthy gums; help overcome infertility in
male smokers; and ease muscle soreness in ath-
letes. Some clinical evidence suggests that vitamin
C from foods can slow the progression of
osteoarthritis. This vitamin may prevent nitrate tol-
erance in patients taking nitroglycerin. When used
vitamin C 655
with vitamin E, vitamin C may prevent pre-
eclampsia in high risk women.
Sources
Fresh vegetables and fresh food are the best sources
of vitamin C, including
CITRUS FRUIT, CANTALOUPE,
green
PEPPERS
, BROCCOLI,
PAPAYA, berries, and green
leafy vegetables. Grains lack vitamin C. Vitamin C
is the most unstable vitamin: In food it is destroyed
by heat and by exposure to air, and cooking and
processing of foods leads to extensive destruction.
Microwave cooking minimizes losses. Destruction
in fruit and vegetables is faster at room tempera-
ture than in the refrigerator, and is fastest if the

vegetable is chopped or peeled. Ascorbic acid pow-
der is stable indefinitely if kept dry.
Requirements
The
RECOMMENDED DIETARY ALLOWANCE (RDA) for
vitamin C is 75 mg for adult women and 90 mg for
adult men. Many nutritional scientists believe the
RDA should be 200 mg. In one study, state plasma
and tissue concentrations of vitamin C were mea-
sured at varying doses in healthy volunteers, after
first being depleted with a vitamin C-deficient diet.
Bioavailability was maximal at 200 mg of vitamin
C per day, higher levels of vitamin C did not appre-
ciably change tissue saturation. Vitamin C needs
are highly individualistic and exposure to pollu-
tants, drugs, medications, smoking, infections, re-
covery from injury or surgery, high stress levels
and heavy drinking often increase the need for
vitamin C above the usual intake. The elderly or
people who rely on medications like aspirin, barbi-
turates, L-dopa, phenacetin, and cortisone need
more vitamin C.
Safety
Vitamin C may have a dark side. Vitamin C
increases iron uptake and hypothetically this could
lead to iron accumulation in those with an inher-
ited tendency to store iron. Iron and vitamin C
spontaneously form free radicals (prooxidant
effect). Excessive vitamin C supplementation
together with excessive iron storage may be detri-

mental. However, under usual physiologic condi-
tions, the amount of free iron would likely be very
small; it would be stored in the iron binding protein
FERRITIN. With injury or inflammation some iron
could be released and could react with hydrogen
peroxide to produce damaging free radicals. In sus-
ceptible people, large amounts of vitamin C could
promote the appearance of oxalate in the urine,
thus increasing the risk of kidney stones. Supple-
menting with magnesium and extra vitamin B
6
can
diminish this risk.
The latest RDA, published in 2000, set a tolerable
upper intake level (UL) for the first time at 2 g. Most
patients who do not exceed this amount will avoid
diarrhea and other gastrointestinal problems associ-
ated with consuming excessive amounts of vitamin
C. Over time this could promote
MALABSORPTION.
Chewable vitamin C can erode tooth enamel, and
taking aspirin with vitamin C can aggravate gastric
bleeding caused by aspirin. Extremely high intakes
of vitamin C may increase the need for
COPPER, and
may increase the risk of
GOUT in individuals who are
genetically susceptible to those conditions. Patients
who are prone to gout or kidney stones or who are
pregnant, should not supplement with vitamin C

without first consulting a physician.
Vitamin C interferes with the effectiveness of
amphetamines, blood thinning drugs, and tricyclic
antidepressants like ritalin, and it can alter lab tests
like urinary glucose and occult blood for bowel
cancer. Patients should tell their doctors they are
taking vitamin C supplements before undergoing
diagnostic laboratory tests. They should also avoid
abruptly quitting daily supplementation of 500 mg
or more, as this can cause short-term scurvylike
symptoms and temporarily lowered resistance to
infections. (See also
DETOXICATION; MEGADOSE.)
Bendich, Adrianne, and Langseth, L. “The Health Effects
of Vitamin C Supplementation: a Review,” Journal of
the American College of Nutrition 14, no. 2 (1995):
124–136.
Carr, A. C. “Toward a New Recommended Dietary
Allowance for Vitamin C Based on Antioxidant and
Health Effects in Humans,” American Journal of Clinical
Nutrition 69, no. 6 (1999): 1,086–1,107.
Muntwyler, J. et al. “Vitamin Supplement Use in a Low-
Risk Population of US Male Physicians and Subse-
quent Cardiovascular Mortality,” Archives of Internal
Medicine 162 (2002): 1,472–1,476.
vitamin D A fat-soluble trace nutrient required
for healthy
BONES and teeth. Vitamin D
2
(ERGOCAL-

656 vitamin D
CIFEROL) occurs in plants, yeast, and fungi. Com-
mercially, vitamin D
2
is produced by exposing a
plant sterol, ergosterol, to UV light. Vitamin D
3
,
cholecalciferol (25-hydroxy cholecalciferol), is the
form found in animal tissue and in the oil of fatty
fish, and it is also synthesized in the skin from a cho-
lesterol derivative when exposed to sunlight (UV
light). Vitamin D is the only
VITAMIN to be formed in
this manner. This fat-soluble vitamin is stored in
fatty tissue as well as in the
LIVER, bones, skin, and
muscle. Vitamin D is required for calcium uptake,
and so is linked to the formation of bones and teeth.
Vitamin D is the only vitamin that is converted
to a
HORMONE. Vitamin D is transported to the
KID-
NEYS, where it is again oxidized, yielding calcitriol
(1,25 dihydroxy cholecalciferol), which is a hor-
mone. Calcitriol in the bloodstream travels to the
intestine where it stimulates the formation of cal-
cium transport proteins. In addition calcitriol can
increase bone rebuilding by working together with
parathyroid hormone. It also stimulates calcium

reabsorption by the kidney.
Vitamin D as calcitriol influences many glands
and tissues. This hormone affects the
PANCREAS
(insulin secretion), the
PARATHYROID GLANDS, PITU-
ITARY GLAND
, ovaries, testes, COLON
, placenta,
uterus, heart,
THYMUS, mammary tissue, and brain
(cerebellum). In a very real sense calcitriol is an
immune enhancer. Calcitriol stimulates
WHITE
BLOOD CELLS
, especially macrophages, and influ-
ences B and T lymphocytes—major classes of cells
responsible for antibody production and the sur-
veillance mechanism of the
IMMUNE SYSTEM.
Possible Roles in Maintaining Health
Chronic vitamin D deficiency in children leads to
RICKETS
, characterized by abnormal calcification of
bones. As a result, bones are soft and become de-
formed. Teeth do not develop normally and are
subject to decay. Rickets is rare in Western societies
owing to the prevalent practice of food
FORTIFICA-
TION with forms of vitamin D.

The adult equivalent of rickets is
OSTEOMALACIA.
In this disease bones become depleted of calcium
and phosphorus. Osteomalacia is more common
during pregnancy and lactation, as well as during
old age. Supplementation with vitamin D can
reduce the risk of osteomalacia. Although vitamin
D is necessary for normal calcium metabolism, it
does not seem to protect against
OSTEOPOROSIS in
postmenopausal women. Osteoporosis is mitigated
by
MAGNESIUM, CALCIUM, and possibly FLUORIDE,
BORON, MANGANESE, and VITAMIN K.
Population studies suggest that vitamin D and
calcium deficiencies account in part for the high
rate of colorectal cancer and breast cancer world-
wide.
CALCIFEROL inhibits cancer cells in the test
tube and inhibits chemically induced cancer in
mice. Vitamin D applied to the skin or taken orally
may clear up psoriasis, a condition characterized by
scaly, itchy red patches of skin.
Sources
There are few good food sources of vitamin D,
which is the least prevalent vitamin in the food
supply. Vitamin D occurs in fatty fish, fish liver oils,
egg yolk, and liver. Vitamin D is used to fortify
MILK, and either vitamin D
3

or vitamin D
2
are used.
Whole milk, low-fat milk, nonfat milk, and nonfat
dry milk are fortified with 400 IUs, equivalent to 10
mcg of vitamin D per quart, although spotchecks
have revealed variations in this level. Other foods
may be fortified with vitamin D: breakfast cereal,
infant cereal, bread, chocolate beverages, and mar-
garine.
Requirements
Human requirements are difficult to establish
because varying levels of this vitamin are synthe-
sized by the skin. The National Institutes of Health
have determined that there is insufficient evidence
to establish a RDA for vitamin D. Instead, scientists
have set an adequate intake (AI), a level of intake
sufficient to maintain healthy blood levels in
adults. For adults between 19 and 50 the AI is 5
mcg. For adults between the ages of 51 and 69 the
amount is 10 mcg, and for people over 70 the AI is
15 mcg. Factors that increase the risk of vitamin D
deficiency include: gallbladder removal, severe
food allergies, poor fat absorption (for instance,
due to
CELIAC DISEASE) and liver disease. Several
medications can interfere with vitamin D uptake:
certain anticonvulsant agents, barbiturates and cor-
tisone. Mineral oil blocks the uptake of this and
other fat-soluble vitamins. People with kidney dis-

ease or diabetes may not be able to activate vitamin
vitamin D 657
D. Institutionalized people who get little exposure
to sunlight, strict vegetarians, and elderly persons
are more at risk for vitamin D deficiency. The effi-
ciency of the skin’s production of this vitamin
declines with age.
Safety
Vitamin D can be toxic, due to high blood calcium
levels (hypercalcemia) and the calcification of soft
tissue. Symptoms include constipation, vomiting,
fatigue, drowsiness, lack of appetite, and, in severe
cases, high blood pressure, kidney stones, and even
kidney failure and coma. Doses at two or three
times the RDA seem unlikely to cause toxicity.
Young children are more susceptible, and as little as
1,800 IU of vitamin D per day may cause toxicity.
Moderately high consumption over a long period
of time may increase the risk of atherosclerosis.
Those with elevated blood calcium levels should
not supplement with vitamin D without medical
supervision. (See also
ENRICHMENT; HYPERVITA-
MINOSIS.)
Fraser, D. R. “Vitamin D,” Lancet 345 (January 14, 1995):
104–107.
vitamin E
(tocopherol) A fat-soluble essential
nutrient that stabilizes cell membranes. Naturally
occurring tocopherols are a mixture of closely re-

lated compounds (isomers) designated alpha-
tocopherol, beta-tocopherol, gamma-tocopherol,
and delta-tocopherol. Alpha-tocopherol has the
greatest vitamin E activity in the body. Synthetic
vitamin E, designated as dl-tocopherol or rac-toco-
pherol, is less active. Supplements usually incorpo-
rate vitamin E bound to simple acids to prevent its
oxidation. Alpha-tocopherol acetate and succinate
are common forms; the acetate and succinate are
forms broken down by intestinal enzymes to
release vitamin E.
Free Radicals Vitamin E is the major lipid
antioxidant in the body, the property for which it is
best known. It squelches free radicals, highly reac-
tive molecules that can attack neighboring mole-
cules and damage polyunsaturated fatty acids in
membrane lipids, proteins, and
DNA, damaging cells
and leading to disease. Free radical damage is
linked to
CANCER, HEART DISEASE, CATARACTS, and
aging. This vitamin plays important roles in the
immune system, the nervous system and the
endocrine (hormonal) system.
Possible Roles in Maintaining Health
Cancer Studies to determine whether vitamin
E is effective in the treatment or prevention of can-
cer have been inconclusive. Some studies have
shown that patients who take supplements of vita-
min E decrease their risk of colon cancer while in

others supplementation had no effect on this can-
cer. Population studies and a clinical trial con-
cluded that a high intake of vitamin E was related
to a decreased incidence of prostate cancer. Popula-
tion studies suggest that low blood levels of vitamin
E and
BETA-CAROTENE correlate with an increased
risk of lung cancer.
Cardiovascular Disease Population studies
suggest that increased vitamin E intake from foods
may reduce the risk of heart disease. Protection
against free radical damage by this vitamin is an
attractive hypothesis. For example, the Physicians
Health Study found that taking vitamin E, vitamin
C, or multivitamins was not associated with a sig-
nificant decrease in death rates from cardiovascular
disease. The study included 83,639 male physicians
in the United States who had no history of heart
disease at baseline and were followed for an aver-
age of 5.5 years. The Heart Outcomes Prevention
Evaluation (HOPE) Study followed almost 10,000
patients who were at high risk for heart attack or
stroke for more than fours years. Participants who
received a daily dose of 265 mg of vitamin E daily
experienced no fewer cardiovascular events or hos-
pitalizations for heart failure or chest pain than did
those participants who were given a sugar pill
(placebo). This study is ongoing, and with addi-
tional time researchers should have a better idea
whether vitamin E is helpful in preventing cardio-

vascular disease.
Gamma-tocopherol Alpha tocopherol is the
form of vitamin found in highest concentration in
blood and tissues due to selection by the intestines
and liver. However, gamma-tocopherol is the most
common form of vitamin E in the diet of typical
Americans. Some studies suggest that alpha-
tocopherol, the form of vitamin E prevalent in
SUP-
PLEMENTS, alone, may be ineffective in reducing the
risk of heart disease. However, according to one
study gamma-tocopherol alone does not seem to
658 vitamin E
protect against heart disease at all. Other studies
have shown that gamma-tocopherol is more bene-
ficial in slowing or stopping the growth of prostate
cancer cells than are other vitamin E compounds.
In the test tube, vitamin E is a potent inhibitor of
LDL oxidation. Oxidation of LDL by free radicals
and its uptake by cells in arterial walls may initiate
the development of
ATHEROSCLEROSIS. However,
most controlled clinical trials found that vitamin E
supplements do not protect against cardiovascular
disease.
Neurologic Disorders Vitamin E plays an
important role in maintaining normal nerve func-
tion. Vitamin E deficiency is usually associated with
symptoms of peripheral
NEUROPATHY. Some studies

suggest that low vitamin E content in nerves pre-
cedes nerve degeneration. Vitamin E has been
found to be beneficial in reducing the severity of
symptoms of
TARDIVE DYSKINESIA
, a side effect of
long-term use of tranquilizers (phenothiazines)
that produces involuntary movements.
Eye Diseases Population studies indicate that
cataract-free people consume more vitamin E and
vitamin C than those with cataracts. Premature
infants can develop vitamin E deficiencies because
they possess almost no
FAT, hence fat-soluble vita-
min stores are marginal. Premature infants receive
vitamin E to prevent anemia and retinopathy. In
another study cigarette smoking seemed to counter
any beneficial effects of taking vitamin E to prevent
cataracts. Together with vitamin C, zinc, and
beta-carotene, vitamin E can decrease the progres-
sion of moderate to severe age-related macular
degeneration.
Immune System Moderate amounts of vitamin
E seem to increase the ability of macrophages to
destroy bacteria and to boost activity of T lympho-
cytes, the foot-soldiers and generals of the
IMMUNE
SYSTEM
. Vitamin E may alter production of certain
PROSTAGLANDINS, hormone-like substances derived

from essential fatty acids that promote
INFLAMMA-
TION. It has been used to manage autoimmune con-
ditions like
LUPUS ERYTHEMATOSUS. Healthy elderly
men and women supplemented with moderate
amounts of vitamin E can show greater immune
responsiveness than those who do not supplement
with this vitamin. On the other hand, very high
levels of vitamin E may inhibit immune function.
Age-related Dementia Two studies showed that
vitamin E may play an important role in maintain-
ing mental function in the elderly. Participants in
one four-year study who took high amounts of vita-
min E had a 70 percent reduction in the risk of
developing
ALZHEIMER’
S DISEASE. In another study
researchers tracked 2,800 men and women between
the ages of 65 and 102 for an average of three years.
During that time 61 percent of the subjects showed
some decline in mental functioning. The rest either
showed no decline or improved. Those who had the
best results were taking the highest amounts of vit-
amin E, and those who showed the sharpest decline
were taking the lowest amounts of the vitamin.
Other Conditions Vitamin E has been used to
treat tardive dyskinesia. It seems to be more effec-
tive for people who have had this condition for less
than five years. The vitamin may normalize retinal

blood flow in type 1 diabetes, and it may control red
blood cell loss with some inherited diseases such as
glucose-6 phosphate dehydrogenase deficiency,
which produces fragile red blood cells. In combina-
tion with vitamin C, vitamin E seems to reduce the
risk of pre-eclampsia in high risk women. There is
some evidence that the vitamin can also reduce
some symptoms of PMS, including anxiety, crav-
ings, and PMS-related depression. Case studies sup-
port claims that vitamin E promotes wound healing
and minimizes scar tissue formation. Vitamin E sup-
plementation has been suggested to reduce symp-
toms of
PREMENSTRUAL SYNDROME. Most careful
studies on the effects of vitamin E supplementation
on muscular strength, maximum oxygen consump-
tion, or endurance have failed to demonstrate ben-
efits. It is possible vitamin E can reduce oxygen debt
and increase maximum oxygen consumption in
adapting to high elevations.
Diabetes Sometimes supplementation with
vitamins can improve glucose tolerance and insulin
sensitivity in diabetic patients, and reduce the level
of secondary damage due to the buildup of glucose-
bound proteins.
Osteoarthritis Vitamin E possesses mild and
inflammatory activity, which may explain why it
can help lessen pain associated with osteoarthritis.
Skin Conditions A variety of skin conditions
such as Raynaud’s phenomenon and polymitosis

have been treated with vitamin E.
vitamin E 659
Sources
The highest levels of vitamin E occur in
VEGETABLE
OILS
(safflower, soybean, and sunflower oils), BUTTER
and MARGARINE, NUTS, wheat germ, whole-grain
CEREALS
, EGGS, and green leafy vegetables. Most
fruits and white bread contain negligible vitamin E.
To obtain 100 IU of vitamin E, a level found to
reduce the risk of heart disease, a person would have
to eat six cups of kale, or 4.5 cups of sweet potatoes.
Vitamin E supplements should not be taken together
with iron because they interfere with each other.
Requirements
The
RECOMMENDED DIETARY ALLOWANCE (RDA) for
vitamin E is 15 mg of alpha tocopherol equivalents.
In a 2000 report the Institutes of Medicine con-
cluded that most adult Americans get enough vita-
min E from their diets to meet daily requirements.
Premature infants, individuals on very-low-
calorie/low-fat diets or who do not absorb fat very
well (including some elderly people) may be defi-
cient. Chronic malabsorption of fat and fat-soluble
vitamins, including vitamin E, can accompany cys-
tic fibrosis,
SPRUE and nontropical sprue, chronic

PANCREATITIS, CELIAC DISEASE, and bile duct inflam-
mation or blockage, among other conditions.
Symptoms of severe vitamin E deficiency in-
clude
ANEMIA and neurologic disorders. Newborn
infants, especially premature infants with vitamin
E deficiency, experience
EDEMA and blood abnor-
malities. The requirement for vitamin E increases
with increased consumption of polyunsaturated
oils due to the increased susceptibility to peroxida-
tion. However, the optimal ratio is unclear. In
extreme situations, the requirement may exceed
the RDA.
Safety
Vitamin E is one of the least toxic fat-soluble vita-
mins when administered orally, and most healthy
adults can tolerate 100 to 800 mg daily. Excessive
vitamin E may cause fatigue, muscle weakness,
stomach upset, headache, nausea, and skin disor-
ders. In certain patients with high blood pressure,
vitamin E may elevate blood pressure. Those with
HYPERTENSION, rheumatic heart disease, or diabetes
should seek medical advice before supplementing
with vitamin E. People taking anticoagulant med-
ications or who are deficient in
VITAMIN K, or who
have blood clots, should follow their physician’s
advice regarding vitamin E supplements to avoid
the potential problem with increased bleeding. Iron

and oral contraceptives can interfere with absorb-
ing vitamin E. (See also
AGING; DEGENERATIVE DIS
-
EASES
; TOCOTRIENOLS.)
Engelhart, M. J. et al. “Dietary Intake of Antioxidants
and the Risk of Alzheimer Disease,” JAMA 287 (2002):
3,223–3,229.
The Heart Outcomes Prevention Evaluation Study Inves-
tigators. “Vitamin E Supplementation and Cardiovas-
cular Events in High-risk Patients,” New England
Journal of Medicine 342 (2000): 154–160.
Meydani, Mohsen. “Vitamin E,” Lancet 345 (January 21,
1995): 170–175.
Morris, M. et al. “Dietary Intake of Antioxidant Nutrients
and the Risk of Incident Alzheimer Disease in a Bira-
cial Community,” Journal of the American Medical Asso-
ciation 287 (2002): 3,230–3,237.
Muntwyler, J. et al. “Vitamin Supplement Use in a Low-
Risk Population of US Male Physicians and Subse-
quent Cardiovascular Mortality,” Archives of Internal
Medicine 162 (2002): 1,472–1,476.
vitamin F See ESSENTIAL FATTY ACIDS.
vitamin H See BIOTIN.
vitamin K A fat-soluble vitamin required for nor-
mal
BLOOD CLOTTING. As with VITAMIN E and VITAMIN
B
6

, the term vitamin K represents several closely
related forms: the most prevalent, naturally occur-
ring forms are vitamin K
1
(philloquinone or
hytonadione) and vitamin K
2
(menaquinone). Vit-
amin K
3
is MENADIONE, a synthetic form that can be
activated in the
LIVER.
Vitamin K serves as a cofactor for the processing
of six proteins required in the complex chain of
reactions that regulates blood clotting. One of these
proteins is prothrombin, the inactive precursor of
the enzyme that creates fibrin clots from fibrino-
gen, and vitamin K has been used to treat clotting
disorders due to vitamin K deficiency. Vitamin K
also assists in the synthesis of osteocalcin, a bone
protein that forms the matrix for mineralization
and bone building.
660 vitamin F
Possible Roles in Maintaining Health
Vitamin K is required for healing fractured bone
and in the maintenance of normal bone. Elderly
patients with osteoporosis (thin bone disease) may
be low in vitamin K. Vitamin K supplementation
may decrease calcium excretion and help protect

against osteoporosis. A deficiency of vitamin K
causes hemorrhaging. Pediatricians administer vit-
amin K to newborn infants to reduce their risk of
spontaneous bleeding. Infants also run the risk of
being permanently brain damaged by vitamin K
deficiency in the first six months of life. There may
be other important functions of this vitamin; vita-
min K-dependent modified proteins occur in kid-
neys and other tissues as well, though their
function is unclear.
Sources
Vitamin K occurs in highest levels in green leafy
vegetables. Dairy products are good sources, and
small amounts occur in cereals, meats, and other
vegetables. Bacteria colonizing the mature small
intestine produce vitamin K;
LACTOBACILLUS ACI-
DOPHILUS is an example of such a beneficial gut bac-
teria. Vitamin K
3
is prescribed to treat vitamin K
deficiencies.
Requirements
The adequate intake for normal adults is 120
mcg/day for men and 90 mcg/day for women.
There are hints that optimal bone metabolism is
more sensitive to inadequate vitamin K and the
needs may be higher. Because vitamin K is widely
distributed in food and is formed by normal gut
flora, vitamin K deficiency is not believed to be

common. Deficiency could occur in people who
consume few vegetables, in people with lipid
MAL-
ABSORPTION
and in those with CELIAC DISEASE or
bile duct obstruction. The prolonged use of oral
antibiotics; certain medications like cholesterol
lowering drugs, mineral oil, anticonvulsants
(Dilantin), and some antibiotics (aphalosporins);
and
PARENTERAL NUTRITION (venous feeding)
increase the risk. Vitamin K status needs to be
monitored in patients being treated with anticoag-
ulants (like coumadin). Symptoms of severe defi-
ciency include a tendency to bleed and disturbed
bone formation.
Safety
Naturally occurring forms of vitamin K are rela-
tively nontoxic. The synthetic form may rarely
cause liver problems. An allergic-type reaction can
occur with high doses. A high intake of vitamin E
may cause bleeding similar to vitamin K deficiency.
Those who have a vitamin K deficiency need med-
ical supervision. Patients taking anticoagulants
should take vitamin K only with the advice of a
physician. (See also
VITAMIN A
; VITAMIN D
.)
vitamin P See FLAVONOIDS

.
VLDL See VERY LOW-DENSITY LIPOPROTEIN.
VLDL 661