The Encyclopedia Of Nutrition And Good Health - R pdf

R
549
radiation preservation of food
See
FOOD IRRADI-
ATION
.
radiation therapy
(radiotherapy) Using carefully
aimed doses of radiation to shrink or destroy cer-
tain types of
CANCER, especially tumors that cannot
be removed safely with surgery. During treatments
highly calibrated equipment bombards cancerous
tumors with high doses of radiation without expos-
ing neighboring healthy tissue. Typically a patient
undergoes daily treatments for two to nine weeks.
As with other cancer treatments such as che-
motherapy, radiation therapy can cause negative
and sometimes dangerous nutrition-related side
effects, including nausea, vomiting, mouth sores,
appetite loss, heartburn, difficulty swallowing,
bloating, and diarrhea. Inadequate nutrition during
radiation therapy can slow healing and recovery.
During this time most patients need to make
sure they eat enough and that they get the right
balance of nutrients to keep up their strength,
decrease the risk of infection, and promote healing.
Some helpful tips include eating a small meal about
an hour before each treatment; eating small, fre-
quent meals throughout the day; and supplement-

ing meals with liquid meal replacements to
increase caloric and protein intake. Patients should
consider seeking the support of a nutritionist to
ensure they are getting the right amount and com-
bination of nutrients during radiation therapy.
Chase, Daniella et al. What to Eat When You Have Cancer.
New York: Contemporary Books, 1996.
radioactivity See CARCINOGEN.
radish (Raphanus sativus) A root vegetable with
a distinctive sharp flavor; related to broccoli, kale,
and cabbage. These cruciferous vegetables possess
anticancer properties. The radish probably origi-
nated in western Asia and was used by Babylonians
and ancient Egyptians. It was introduced to China
around 500
B.C., where new varieties were devel-
oped with a tangy flavor. According to the variety,
radishes may be round, tapered, or oblong, and the
color can be white, red, yellow, purple, or black.
The Oriental radish, daikon, can weigh up to 5 lb.
(2.3 kg). The common radish (red globe) is usually
eaten raw as a condiment and as a salad vegetable.
Black radishes are the size of turnips; their flesh is
white and very pungent. Radishes can be cooked as
a vegetable, added to soups, or pickled. The nutri-
ent contents of 10 radishes (raw, 45 g) is 7 calories;
protein, 0.27 g; carbohydrate, 1.6 g; fiber, 0.24 g;
vitamin C, 10 mg; riboflavin, 0.02 mg; niacin,
0.135 mg.
radon See CARCINOGEN.

raisin A dried form of several varieties of grapes.
Half of the world’s supply of raisins comes from the
San Joaquin Valley of California. Muscat, Sultana,
Thompson Seedless, and Zante Currant represent
the principal varieties of grapes suitable for raisins.
Ripe grapes are dehydrated either mechanically or
are sun-dried so that raisins contain 17 percent
water, compared to about 80 percent for grapes.
Nutrients like sugar are much more concentrated
in raisins than in the fresh fruit, and raisins are a
good source of iron, potassium, B vitamins, dietary
fiber, and carbohydrate (calories). Golden raisins
are dried Thompson Seedless grapes that have been
treated with sulfur dioxide then dehydrated in
forced dry air. Other varieties include currants
(from Black Corinth grapes); Sultanas (from a large
green grape), popular in Europe; Muscat raisins
(from green Muscat grapes), which are fruity fla-
vored and often used in fruit cakes. Unopened
packages of raisins can be stored a year when
refrigerated, longer when frozen. The nutrient con-
tent of 1 cup (seedless, 145 g) is: 435 calories; pro-
tein, 4.7 g; carbohydrate, 115 g; fiber, 9.6 g; fat, 0.7
g; iron, 3.0 mg; potassium, 1,089 mg; vitamin C, 5
mg; thiamin, 0.23 mg; riboflavin, 0.13 mg; niacin,
1.29 mg.
rancidity The process by which fats and oils
become oxidized through exposure to air. Rancid
fat has an “off” flavor and a disagreeable odor. In
meat, iron-containing protein react with oxygen to

produce free radicals that cause loss of flavor
accompanying fat decomposition. The oxidation of
fats usually occurs spontaneously, though slowly,
at room temperature. Exposure to heat, light, and
trace metals like
IRON greatly speeds the reaction of
oxygen. Rancidity lowers the content of other
lipids, including
VITAMIN A and VITAMIN E. Thus, the
rancid foods are less wholesome and less nutritious
than fresh foods.
At a molecular level, oxygen and a reactive
chemical species called
FREE RADICALS, molecules
that are electron deficient, can attack unsaturated
FATTY ACIDS in fats and oils. Unsaturated fatty acids
contain double bonds that lack pairs of hydrogen
atoms. These bonds are fragile and susceptible to
chemical modification, leading to the formation of
PEROXIDES, which are potent intermediates in fat
oxidation. Lipid peroxides can trigger
INFLAMMA-
TION and spontaneously decompose into more free
radicals plus fragments that are both cytoxic (cell
killing) and mutagenic (causing mutations).
Most cells contain an antioxidant enzyme sys-
tem called
GLUTATHIONE PEROXIDASE that converts
unstable oxidized lipids (lipid peroxides) to harm-
less fatty acids that can be used for energy.

A growing family of
FOOD ADDITIVES called
ANTIOXIDANTS is used to control or prevent oxida-
tion of processed vegetable oils and processed foods
containing fats and oils in order to increase their
stability during storage. Ascorbic acid (
VITAMIN C)
and vitamin E prevent oxidative damage, and addi-
tives like
CITRIC ACID can bind metal ions that could
otherwise catalyze a reaction with oxygen. Syn-
thetic antioxidants, including BHA, BHT, and
PROPYL GALLATE, are designed to disarm free radicals
before they can cause damage. Because of the
safety concerns raised about synthetic antioxidants,
the food industry has studied naturally occurring
antioxidants that can be added to foods and fats
and oils to stabilize them. As an example, rosemary
extracts have proven effective in stabilizing veg-
etable oils. (See also
FOOD PRESERVATION.)
rapeseed
(Brassica napus; B. campestris) One of
the five most important oil-producing seed crops
and the only oil seed successfully grown world-
wide. The origins of rapeseed are obscure, although
reference to it is made in 3,000-year-old Sanskrit
writings. The seed contains 40 percent to 50 per-
cent oil. Rapeseed oil typically contains erucic acid,
a fatty acid analog that interferes with

FAT METABO-
LISM
in experimental animals when consumed in
large amounts. New strains of rapeseed that con-
tain little of this acid or another antinutrient, glu-
cosinolate, were developed in Canada and Europe.
The oil derived from the new strains of rapeseed,
CANOLA OIL, contains significantly more OLEIC ACID,
the monounsaturate of
OLIVE OIL. The fatty acid
composition of canola oil resembles olive oil and it
too is classified as a monounsaturate. Canola oil is
used in
SHORTENING, MARGARINE, salad oil, MAYON-
NAISE, and as a cooking oil. It contains 6.9 percent
saturated fatty acids; 34.6 percent polyunsaturated
fatty acids; and 58.5 percent monounsaturated
fatty acids. (See also
VEGETABLE OIL.)
raspberry (Rubus spp.) The FRUIT of a family of
brambles (Rosaceae) that includes
BLACKBERRY and
loganberry. Raspberries resemble blackberries,
except the berry core remains on the vine when
raspberries are picked. Each fruit is composed of
tiny drupes, each of which can be considered a
fruit. Raspberries apparently originated in eastern
Asia. They now grow wild from the Arctic Circle to
northern South America. Cultivation was probably
initiated in Europe in the 16th century. Red rasp-

berries are the most common variety in America,
but they may be yellow, black, or purple as well.
Oregon and Washington are major raspberry pro-
ducers. Ninety percent of the U.S. crop is processed,
and most is quick frozen because it has a short shelf
life. Most red or dark blue-purple berries contain
550 rancidity
pigments (ANTHOCYANINS) that have beneficial
effects on connective tissue and inflammation.
These and related berries contain ellagic acid, a
substance that may help prevent some forms of
cancer. Raspberries are good sources of
FIBER,
POTASSIUM
, and VITAMIN C
. The nutrient contents of
1 cup (raw, 123 g) are: 60 calories; protein, 1.1 g;
carbohydrate, 14.2 g; fiber, 9.1 g; fat, 0.7 g; potas-
sium, 187 mg; vitamin C, 31 mg; thiamin, 0.04 mg;
riboflavin, 0.11 mg; niacin, 1.11 mg. (See also
FLAVONOIDS
.)
raw fish See
SEAFOOD.
raw meat disease See TOXOPLASMOSIS.
raw milk See MILK.
raw shellfish See SHELLFISH.
raw sugar See SUCROSE.
RD See DIETITIAN.
RDA See USRDA.

recommended daily allowances See
USRDA.
Recommended Dietary Allowances
(RDA) The
Food and Nutrition Board of the U.S. National
Academy of Sciences has periodically published
recommended average daily intakes for several
nutrients selected as adequate to meet the dietary
needs of most healthy Americans. Generally, the
RDAs were reviewed every five years or so, the
most recent edition being 1989. RDAs were estab-
lished for the following categories:
•
ENERGY;
• fat-soluble
VITAMINS: VITAMINS A, VITAMIN D, VIT-
AMIN E, VITAMIN K (added in 1989);
• water-soluble
VITAMINS: VITAMIN C, FOLIC ACID,
NIACIN, RIBOFLAVIN, THIAMIN, VITAMIN B
6
, VITAMIN
B
12
;
• macrominerals:
CALCIUM, MAGNESIUM, PHOS-
PHORUS;
• trace minerals:
IODINE, IRON, ZINC, MAGNESIUM,

SELENIUM (added in 1989).
The RDAs have been replaced by a new set of
dietary recommendations called
DIETARY REFERENCE
INTAKES
(DRI). These are meant to shift nutritional
focus from deficiency to lowering the risk of dis-
ease. They reflect the latest research on what levels
of nutrition are best to combat diseases such as can-
cer, osteoporosis, and
CORONARY ARTERY DISEASE.
The DRIs incorporate the RDAs along with three
other nutrient-based reference values: the esti-
mated average requirement (the daily intake esti-
mated to meet the nutrient requirements of people
in a specific age or gender group); the adequate
intake (when an estimated average requirement is
not available, this intake level is determined based
on observing what amount of nutrients sustain
health in a specific group of people); and the toler-
able upper intake level (the daily nutrient intake
that is unlikely to pose risks of adverse health
effects to almost all healthy people of a specific age
or gender).
The RDAs are based on population needs. Groups
referred to in the RDA tables include: infants; chil-
dren between the ages of one and three; between
four and six; and between seven and ten; males or
females between the ages of 11 and 14; between 15
and 18, 19 and 22, 23 and 50; men and women over

50; pregnant women; and lactating women.
All recommendations except for energy intend
that nutrient intake will exceed the requirements
of most healthy people. This decision was made in
order to address the problem of variability in indi-
vidual nutrient needs. Mathematically, RDAs have
been chosen to cover 97.5 percent of a given group
of people by selecting values lying between two
standard deviations above the mean nutrient
requirement for a population.
The determination of the RDAs for energy dif-
fers significantly from other recommendations for
specific nutrients. The allowances for energy
employ the average (mean) requirement for each
population reported. The mean was chosen be-
cause a higher recommended energy allowance
would significantly increase the odds that many
people, who have average energy needs, would
become overweight.
Recommended Dietary Allowances 551
The RDAs were selected after evaluating evi-
dence that comes from animal as well as human
studies. Nutrient requirements are generally set
at levels that ensure that body stores are adequate
for normal functions, growth, and development. In
people, the nutrient turnover and rates of deple-
tion of nutrient body pools are most usually un-
known. Therefore experimental evidence for
setting the RDAs generally relies on the following:
intakes that maintain adequate blood levels; excre-

tion of surplus doses in urine or feces; maintenance
of a balance of intake and body losses; measure-
ment of body function or metabolic process;
knowledge of the amount of a nutrient needed to
prevent or even cure disease in humans and some-
times in experimental animals; and examination of
nutrient intakes of apparently healthy people. (See
also
FOOD GUIDE PYRAMID.)
King, J. “The Need to Consider Functional Endpoints in
Defining Nutrient Requirements,” American Journal of
Clinical Nutrition 63 (1996): 983S–984S.
Recommended Nutrient Intakes (for Canadians)
(RNI) The Canadian version of the U.S. Recom-
mended Dietary Allowances. The RNIs are being
replaced by the
DIETARY REFERENCE INTAKES, estab-
lished by Canadian and U.S. scientists according to
a review process overseen by the Food and Nutri-
tion Board of the U.S. National Academy of Sci-
ences.
red blood cells
(erythrocytes) The major type of
cells in blood. Red blood cells transport
OXYGEN to
all cells of the body, and their color reflects the high
content of
HEMOGLOBIN, the red oxygen transport
protein. The importance of red blood cells is indi-
cated by their numbers: The average person has 35

trillion red blood cells. Males have about 5 million
red blood cells per milliliter of blood and females
have about 4.5 million per milliliter. Each red blood
cell contains about 280 million hemoglobin (pro-
tein) molecules. The blood of the average adult
male contains 14 to 16.5 g of hemoglobin per 100
ml of blood; the average adult female has 12 to 14
g per 100 ml.
Inhalation brings fresh air into the lungs where
hemoglobin binds oxygen, which is then carried to
tissues via arteries. Oxygen binding is reversible so
552 Recommended Nutrient Intakes
COUNCIL FOR RESPONSIBLE NUTRITION
Minerals: Historical Comparison or RDIs, RDAs, and DRIs, 1968 to Present
NUTRIENT RDI* 1968 RDA** 1974 RDA** 1980 RDA** 1989 RDA** DRIs***
Calcium 1000 mg 1300 mg 1200 mg 1200 mg 1200 mg 1300 mg
Phosphorus 1000 mg 1300 mg 1200 mg 1200 mg 1200 mg 1250 mg
(700 adult)
Iron 18 mg 18 mg 18 mg 18 mg 15 mg 18 mg
Iodine 150 mcg 150 mcg 150 mcg 150 mcg 150 mcg 150 mcg
Magnesium 400 mg 400 mg 400 mg 400 mg 400 mg 420 mg
Zinc 15 mg 10-15 mg 15 mg 15 mg 15 mg 11 mg
Selenium 70 mcg – – 70 mcg 55 mcg
Copper 2 mg – – 2–3 mg 1.5–3 mg 0.9 mg
Manganese 2 mg – 2.5–7 mg 2.5–5 mg 2–5 mg 2.3 mg
Chromium 120 mcg – – 50–200 mcg 50–200 mcg 35 mcg
Molybdenum 75 mcg – 45–500 mcg 150–500 mcg 75–250 mcg 45 mcg
* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling. It was based
initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.
** The RDAs were established and periodically revised by the Food and Nutrition Board. Value shown is the highest RDA for each nutrient, in the

year indicated for each revision.
*** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the
Institute of Medicine, 1997–2001. They replace previous RDAs, and may be the basis for eventually updating the RDIs. The value shown here is
the highest DRI for each nutrient.
Council for Responsible Nutrition, 2001
1875 I Street N.W. Suite 400, Washington, D.C. 20006 • (202) 872-1488
red blood cells 553
COUNCIL FOR RESPONSIBLE NUTRITION
Minerals: Comparison of Current RDIs, New DRIs, and ULs
MINERAL CURRENT RDI* NEW DRI** UL***
Calcium 1000 mg 1300 mg 2500 mg
Iron 18 mg 18 mg 45 mg
Phosphorus 1000 mg 1250 mg 4000 mg
Iodine 150 mcg 150 mcg 1100 mcg
Magnesium 400 mg 420 mg 350 mg#
Zinc 15 mg 11 mg 40 mg
Selenium 70 mcg 55 mcg 400 mcg
Copper 2 mg 0.9 mg 10 mg
Manganese 2 mg 2.3 mg 11 mg
Chromium 120 mcg 35 mcg ND
Molybdenum 75 mcg 45 mcg 2000 mcg
* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling. It was based
initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.
** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the
Institute of Medicine, 1997–2001. They replace previous RDAs, and may be the basis for eventually updating the RDIs. The value shown here is
the highest DRI for each nutrient.
*** The Upper Limit (UL) is the upper level of intake considered to be safe for use by adults, incorporating a safety factor. In some cases, lower
ULs have been established for children.
# Upper limit for magnesium applies only to intakes from dietary supplements or pharmaceutical products, not including intakes from food and
water.

ND Upper Limit not determined. No adverse effects observed from high intakes of the nutrient.
Council for Responsible Nutrition, 2001
1875 I Street N.W. Suite 400, Washington, D.C. 20006 • (202) 872-1488
COUNCIL FOR RESPONSIBLE NUTRITION
Vitamins: Historical Comparison of RDIs, RDAs, and DRIs, 1968 to Present
NUTRIENT RDI* 1968 RDA** 1974 RDA** 1980 RDA** 1989 RDA** DRIs***
Vitamin A 5000 IU 5000 IU 1000 RE 1000 RE 1000 RE 900 mcg
(5000 IU) (3000 IU)
Vitamin C 60 mg 60 mg 45 mg 60 mg 60 mg 90 mg
Vitamin D 400 IU 400 IU 400 IU 10 mcg 10 mcg 15 mcg
(10 mcg) (10 mcg) (10 mcg) (400 IU) (400 IU) (600 IU)
Vitamin E 30 IU (20 mg) 30 IU (20 mg) 15 IU (10 mg) 10 mg (15 IU) 10 mg (15 IU) 15 mg #
Vitamin K 80 mcg – – 70–140 mcg 80 mcg 120 mcg
Thiamin 1.5 mg 1.5 mg 1.5 mg 1.5 mg 1.5 mg 1.2 mg
Riboflavin 1.7 mg 1.7 mg 1.8 mg 1.7 mg 1.8 mg 1.3 mg
Niacin 20 mg 20 mg 20 mg 19 mg 20 mg 16 mg
Vitamin B
6
2 mg 2 mg 2 mg 2.2 mg 2 mg 1.7 mg
Folate 0.4 mg 400 mcg 400 mcg 400 mcg 200 mcg 400 mcg food,
(400 mcg) 200 mcg
synthetic ##
Vitamin B
12
6 mcg 6 mcg 3 mcg 3 mcg 2 mcg 2.4 mcg ###
Biotin (300 mcg) 150–300 mcg 100–300 mcg 100–200 mcg 30–100 mcg 30 mcg
Pantothenic acid 10 mg 5–10 mg 5–10 mg 4–7 mg 4–7 mg 5 mg
Choline – – – – – 550 mg
* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling. It was based
initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.

** The RDAs were established and periodically revised by the Food and Nutrition Board. Value shown is the highest RDA for each nutrient, in the
year indicated for each revision.
*** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the
Institute of Medicine, 1997–2001. They replace previous RDAs, and may be the basis for eventually updating the RDIs. The value shown here is
the highest DRI for each nutrient.
(continues)
that hemoglobin releases oxygen in tissues where
there is a low concentration of oxygen. Elevated
CARBON DIOXIDE concentration and acid production
from actively metabolizing tissues also promote
oxygen release from red blood cells. Released oxy-
gen diffuses into cells where it oxidizes fuels to car-
bon dioxide. Red blood cells pick up carbon dioxide
for the return trip to the lungs via blood vessels.
Red blood cells transport about 23 percent of car-
bon dioxide in this manner. In the lungs red blood
cells release carbon dioxide and again bind incom-
ing oxygen.
Red blood cells are highly specialized. The disk
shape presents a larger surface area than a sphere,
which helps the diffusion of oxygen into the cells.
Red blood cells lack a nucleus and
MITOCHONDRIA
and therefore cannot divide, nor use oxygen to
derive energy from the oxidation of fuel molecules.
Instead they rely on
GLYCOLYSIS, an oxygen-inde-
pendent mechanism for oxidation of glucose
554 red blood cells
# Historical vitamin E conversion factors were amended in the DRI report, so that 15 mg is defined as the equivalent of 22 IU of natural vitamin E

or 33 IU of synthetic vitamin E.
## It is recommended that women of childbearing age obtain 400 mcg of synthetic folic acid from fortified breakfast cereals or dietary supple-
ments, in addition to dietary folate.
### It is recommended that people over 50 meet the B
12
recommendation through fortified foods or supplements, to improve bioavailability.
Council for Responsible Nutrition, 2001
1875 I Street N.W. Suite 400, Washington, D.C. 20006 • (202) 872-1488
COUNCIL FOR RESPONSIBLE NUTRITION
Vitamins: Comparison of Current RDIs, New DRIs, and ULs
VITAMIN CURRENT RDI* NEW DRI** UL***
Vitamin A 5000 IU 900 mcg (3000 IU) 3000 mcg (10,000 IU)
Vitamin C 60 mg 90 mg 2000 mg
Vitamin D 400 IU (10 mcg) 15 mcg (600 IU) 50 mcg (2000 IU)
Vitamin E 30 IU (20 mg) 15 mg # 1000 mg
Vitamin K 80 mcg 120 mcg ND
Thiamin 1.5 mg 1.2 mg ND
Riboflavin 1.7 mg 1.3 mg ND
Niacin 20 mg 16 mg 35 mg
Vitamin B
6
2 mg 1.7 mg 100 mg
Folate 400 mcg (0.4 mg) 400 mcg from food, 1000 mcg synthetic
200 mcg
synthetic ##
Vitamin B
12
6 mcg 2.4 mcg ### ND
Biotin 300 mcg 30 mcg ND
Pantothenic acid 10 mg 5 mg ND

Choline Not established 550 mg 3500 mg
* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling. It was based
initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.
** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the
Institute of Medicine, 1997–2001. They replace previous RDAs, and may be the basis for eventually updating the RDIs. The value shown here is
the highest DRI for each nutrient.
*** The Upper Limit (UL) is the upper level of intake considered to be safe for use by adults, incorporating a safety factor. In some cases, lower
ULs have been established for children.
# Historical vitamin E conversion factors were amended in the DRI report, so that 15 mg is defined as the equivalent of 22 IU of natural vitamin E
or 33 IU of synthetic vitamin E.
## It is recommended that women of childbearing age obtain 400 mcg of synthetic folic acid from fortified breakfast cereals or dietary supple-
ments, in addition to dietary folate.
### It is recommended that people over 50 meet the B
12
recommendation through fortified foods or supplements, to improve bioavailability.
ND Upper Limit not determined. No adverse effects observed from high intakes of the nutrient.
Council for Responsible Nutrition, 2001
1875 I Street N.W. Suite 400, Washington, D.C. 20006 • (202) 872-1488
COUNCIL FOR RESPONSIBLE NUTRITION (continued)
(BLOOD SUGAR) to LACTIC ACID. The surface of the
red blood cell possesses certain carbohydrate clus-
ters (blood group substances) that are the basis for
blood typing; for example, according to the ABO
blood groups and Rh blood groups.
Formation
ERYTHROPOIESIS
refers to the process of red blood
cell formation. During embryonic development,
red blood cells are produced by the yolk sac, liver,
spleen, thymus gland, lymph nodes, and bone

marrow, while in adults, red blood cells come
from the bone marrow of long bones like the
femur, and from the cranium, sternum, ribs, ver-
tebrae, pelvis, and lymphoid tissues. The initial
parent cells are called hemocytoblasts. These cells
differentiate into proerythroblasts, an intermedi-
ate stage that eventually differentiates into reticu-
locytes (immature red blood cells), and finally into
mature red blood cells (erythrocytes). The usual
fraction of reticulocytes in blood is between 0.5
percent and 1.5 percent. The percentage increases
with
ANEMIA, when the number of functional red
blood cells becomes inadequate; with bleeding;
hemolysis (rapid breakdown of red blood cells);
and in response to supplementation for
IRON
deficiency.
The kidney stimulates the production of the
hormone, erythropoietin, which stimulates the
production of red blood cells in response to low-
ered oxygen pressure, as experienced at high ele-
vations. When the body suddenly needs more red
blood cells, the kidneys become oxygen-deficient
and release an enzyme that converts a blood pro-
tein to erythropoietin.
The levels of red blood cells represent a balance
between the formation and destruction of red
blood cells. Aged red blood cells are destroyed by
the spleen and by the liver. The protein portion of

hemoglobin is degraded to
AMINO ACIDS; the red
pigment,
HEME, is degraded to BILE PIGMENT, biliru-
bin, which is excreted, and releases iron, which is
reused.
A number of nutrients besides iron support cell
division and protein synthesis in general, and red
blood cell formation in particular:
FOLIC ACID, PYRI-
DOXINE, VITAMIN B
12
, and amino acids. ANTIOXI-
DANTS like VITAMIN E help maintain the red blood
cell membrane and prevent fragility. Deficiencies
of any of these nutrients can cause anemia, a con-
dition resulting from an inadequate level of func-
tional red blood cells. Several inborn errors of
metabolism (mutations) cause abnormal hemo-
globins to be formed. These in turn can alter
the shape of red blood cells and shorten their life
span, resulting in anemia. Sickle-cell anemia and
glucose 6 phosphate dehydrogenase deficiency
are the most common. (See also
HEMATOCRIT; LEU
-
KOCYTES.)
red dye numbers 2, 3, 40 See
ARTIFICIAL FOOD
COLORS

.
red meat See MEAT.
red tide Refers to a plankton bloom often occur-
ring in marine waters during the late summer and
fall. The term red tide comes from the red-brown
color of plankton. The plankton produce a nerve
poison that can accumulate to dangerous levels in
shellfish such as
CLAMS and mussels although it
does not affect the shellfish. Eating contaminated
clams, mussels, and oysters causes paralytic shell-
fish poisoning. The adage of avoiding shellfish dur-
ing months that end in the letter “r”—September,
October, November, and December—is no longer
appropriate because red tide alerts now occur in
other months. Red tide warnings by county health
departments can be issued as early as April.
Symptoms of paralytic shellfish poisoning in-
cludes stomach cramps, dizziness, difficulty in
breathing, and tingling mouth. Symptoms can
appear up to two hours after eating contaminated
shellfish; in severe cases, poisoning can be fatal.
There is no antidote. Immediate medical attention
is mandated. (See also
SEAFOOD.)
Reference Daily Intake (RDI) A replacement
term for “USRDA” (Recommended Daily Allow-
ance), a set of reference values introduced in 1973
to be used for vitamins, minerals, and protein to
help consumers evaluate the nutritional content

for food labels. For the time being, RDIs are identi-
cal to the USRDAs except for protein, which is
adjusted to the specific needs of different age
groups.
Reference Daily Intake 555
NUTRIENT AMOUNT
Vitamin A 5,000 International Units (IU)
Vitamin C 60 milligrams (mg)
Thiamin 1.5 mg
Riboflavin 1.7 mg
Niacin 20 mg
Calcium 1.0 gram (g)
Iron 18 mg
Vitamin D 400 IU
Vitamin E 30 IU
Vitamin B
6
2.0 mg
Folic acid 0.4 mg
Vitamin B
12
6 micrograms (mcg)
Phosphorus 1.0 g
Iodine 150 mcg
Magnesium 400 mg
Zinc 15 mg
Copper 2 mg
Biotin 0.3 mg
Pantothenic acid 10 mg
(Based on National Academy of Sciences’ 1968 Recommended Diet-

ary Allowances.)
Additions Jan. 1, 1997
Vitamin K 80 mcg
Molybdenum 75 mcg
Chloride 3,400 mg
Manganese 2.0 mg
Selenium 70 mcg
Chromium 120 mcg
reference protein A source of PROTEIN used as a
basis for comparing food proteins according to their
amino acid compositions. Reference proteins pro-
vide all essential amino acids in sufficient quantity
to meet the needs of infants and children, who
require substantially more protein than adults,
based on their body weight, to support their higher
growth rates. Another property of reference pro-
teins is that they are highly digestible. High-quality
protein sources often used as reference proteins
include egg, human milk, meat, and fish. The
amino acid patterns for human milk and whole egg
protein are as follows:
Amino Acid Human Milk Whole Egg
mg/100 g mg/100g
Histidine 23 24
Isoleucine 56 63
Leucine 95 88
Lysine 68 68
Methionine and
cysteine 40 56
Phenylalanine and

tyrosine 99 98
Threonine 46 49
Tryptophan 17 16
Valine 63 72
The CHEMICAL SCORE
attempts to measure the
nutritive value of food protein in comparison with
a reference protein. In this case, the amount of the
least abundant limiting essential amino acid in the
test protein is expressed as a percentage of that
amino acid in the reference protein. Thus, a good-
quality protein source could have a chemical score
of 70 or above. Most meat and dairy protein fall
into this category. (See also
BIOLOGICAL VALUE; PRO-
TEIN COMPLEMENTATION; PROTEIN EFFICIENCY RATIO.)
refined carbohydrates Highly purified SUGARS
or
STARCHES. These substances occur in sweeteners
and in products that are mainly starch. Each type of
refined carbohydrate supplies the same four calo-
ries per gram. Purified simple sugars and starches
represent
EMPTY CALORIES, that is, calories lacking
in
VITAMINS, FIBER, PROTEIN, and MINERALS.
One of the most common refined carbohydrates
is table sugar (
SUCROSE), highly purified from sugar
beets or sugar cane by repeated crystallization. The

following sweeteners are only slightly less purified
forms of sucrose: brown sugar, caramelized sugar,
HONEY
, MOLASSES, and turbinado sugar.
Other refined sugars besides sucrose serve as
common
FOOD ADDITIVES:
• Dextrose (grape sugar) is another name for the
pure compound of
GLUCOSE, used by food man-
ufacturers. Dextrose occurs in corn syrup.
• Maltodextrins are starch fragments containing
several glucose units. They yield glucose when
digested and provide no other nutrients.
• Fructose (fruit sugar) occurs as high
FRUCTOSE
CORN SYRUP
. This sweetener also contains glu-
cose, but no other nutrient.
• Sugar alcohols function as sweeteners:
MANNI-
TOL
, SORBITOL, and XYLITOL. None provides any-
thing other than calories to overall nutrition.
Refined Starches
Purified starches are isolated from
WHEAT, CORN,
and
POTATOES, among other sources. Starch is used
556 reference protein

as a thickener in many foods. White flour is a sta-
ple of the American diet. Though not pure starch,
white flour and products prepared from white
bread—cold
BREAKFAST CEREALS, muffins, PASTRY,
pancake mix, pasta (spaghetti, noodles), and the
like—contain much less of the vitamins, minerals,
essential oils, and fiber than are found in the whole
grain from which they were derived. Milling wheat
separates the starchy endosperm from the highly
nutritious germ and bran (the hull of the seed or
kernel).
Recent dietary guidelines have consistently
emphasized minimally processed foods like
FRUIT
and
VEGETABLES. U.S. DIETARY GUIDELINES FOR AMER
-
ICANS (2000) recommend eating sweets sparingly
and suggest that whole grains, vegetables, and
fruits are the foundation of a healthy diet. The
1992
FOOD GUIDE PYRAMID of the USDA recom-
mends three to five servings of vegetables, two to
four servings of fruit and six to 11 servings of rice,
bread, cereal, and pasta daily, with the admonition
to use sweets and added sugar sparingly. (See also
CARBOHYDRATE METABOLISM; NATURAL SWEETENERS.)
reishi mushroom (Ganoderma lucidurn, ling-
zhi) A fungus native to East Asia, where it has

been used since ancient times to treat a variety of
ailments and diseases, including ulcers, cancer, and
insomnia. Its Chinese name, ling-zhi, means “herb
of spiritual potency.”
The fungus grows on rotting logs and stumps.
The fruiting part of the fungus is a mushroom,
which has been harvested by Chinese herbalists for
at least 4,000 years. The mushroom’s flesh can be
eaten whole, but because it is hard and bitter it is
more often cut up or dried for use in teas.
Few reliable studies have been done to support
reishi’s medicinal uses. However, researchers at a
Chinese university discovered that the fungus con-
tains a high level of polysaccharides, which are
known to stimulate the body’s immune system.
Safety data are inadequate for pregnant and
breast-feeding women.
renin An enzyme produced by the KIDNEYS that
helps increase blood pressure. In response to a drop
in
BLOOD PRESSURE, renin activates the HORMONE,
ANGIOTENSIN, which in turn stimulates the ADRENAL
GLANDS
to produce ALDOSTERONE, the hormone that
directs the kidneys to retain
SODIUM and water. Ele-
vated levels of renin correlate with increased risk of
heart attack among people with moderate high
blood pressure (
HYPERTENSION). Possibly too much

angiotensin can trigger reduced blood flow to the
heart. (See also
CARDIOVASCULAR DISEASE; PROTEASE.)
rennet An extract from the stomach of rumi-
nants, such as calves, that contains the enzyme
rennin. Cheese production relies on the action of
rennin that coagulate the proteins in milk, forming
solid curds (from which cheese is made) and liquid
whey. (See also
DENATURED PROTEIN.)
respiration, cellular The use of oxygen by cells to
burn fuel nutrients for energy.
OXYGEN delivered by
the blood is taken up by
MITOCHONDRIA, particles in
the cytoplasm that function as the cell’s power-
houses. Mitochondrial enzymes completely oxidize
FAT, CARBOHYDRATE, and AMINO ACIDS to CARBON
DIOXIDE
and chemical energy released by this
process is trapped as
ATP. ATP is the energy cur-
rency of cells; it provides the necessary energy for
the synthesis of cellular components—proteins,
RNA, DNA—as well as for transmission of nerve
impulses, muscle contraction and the transport of
nutrients across cell membranes. Carbon dioxide
diffuses out of cells into the bloodstream, which
transports it to the lungs to be expired. Respiration
requires specialized enzyme machinery called the

terminal
ELECTRON TRANSPORT CHAIN. This sequence
of linked oxidation-reduction enzymes receives
electrons from individual oxidation reactions of the
cell and passes them on to oxygen, which is con-
verted to water. The sequential transfer of electrons
to oxygen is coupled with the generation of ATP, a
process called
OXIDATIVE PHOSPHORYLATION.
Certain toxins and poisons like cyanide inhibit
cellular respiration, limit ATP production and may
ultimately cause death. Nutrients required to
support respiration include B vitamins
NIACIN, RIBO-
FLAVIN, THIAMIN, PANTOTHENIC ACID, and trace miner-
als like
COPPER and IRON. Another nutrient that may
be required in the diet under certain conditions is
COENZYME Q. This lipid helps funnel electrons into
the system. (See also
CARBOHYDRATE METABOLISM; FAT
METABOLISM
; RESPIRATORY QUOTIENT.)
respiration, cellular 557
respiratory chain See ELECTRON TRANSPORT
CHAIN
.
respiratory quotient (RQ) The ratio of the vol-
ume of expired
CARBON DIOXIDE to the volume of

OXYGEN consumed. This measurement can be used
to determine whether
PROTEIN, CARBOHYDRATE
, and
FAT
represent the major energy sources of the body.
Carbohydrate and protein are more oxidized
(contain more oxygen), and less oxygen is required
to oxidize them completely to carbon dioxide.
Therefore, their RQ values are higher than that of
fat: carbohydrate, 1.0; protein, 0.80; fat, 0.71;
mixed diet, 0.82. The RQ may exceed 1.0 if large
amounts of carbohydrate are being converted to
fat. (See also
METABOLISM.)
resveratrol A substance found in the skin of red
GRAPEs frequently used to make red WINE and grape
juice. Resveratrol is a chemical that acts as an
antibiotic in the plants that produce it. Although it
is found in the components of other plants, includ-
ing peanuts and eucalyptus, it appears in red grape
skin in high concentrations.
Resveratrol is responsible in part for the
CHOLES-
TEROL
-lowering effect of red wine as determined by
animal studies. It has also been suggested as the
possible explanation for the “French Paradox,” the
low incidence of heart disease among French citi-
zens who regularly eat high-fat foods and drink red

wine. Additional research on humans is needed to
determine whether supplementation with resvera-
trol would benefit patients at risk of cholesterol-
related heart disease, and to establish the safety of
this supplement. Several studies have confirmed
that resveratrol is an effective and powerful
ANTIOXIDANT. Consequently, researchers are investi-
gating its possible role in preventing or inhibiting
the growth of
CANCER cells.
Kopp, P. “Resveratrol, a Phytoestrogen Found in Red
Wine. A Possible Explanation for the Conundrum of
the ‘French Paradox’?” European Journal of Endocrinol-
ogy 138 (1998): 619–620.
retinal The biologically activated form of VITAMIN
A
required to form visual purple (rhodopsin), the
pigment in the retina responsible for night vision.
The enzymatic conversion of vitamin A to retinal
requires the trace mineral
ZINC. (See also NIGHT
BLINDNESS
.)
retinoic acid
(9-cis retinoic acid) An oxidized
form of
VITAMIN A, believed to be a new, fat-soluble
HORMONE
. Cis retinoic acid may guide normal
embryonic development and regulate normal cell

division and may be involved in regulating blood
CHOLESTEROL
levels. CANCER is characterized by
uncontrolled cell division; some patients with cer-
tain kinds of cancer, such as leukemia, respond to
treatments with retinoic acid. In 2002 Dartmouth
Medical School researchers reported a significant
discovery related to retinoic acid that may be an
important step in eventually finding a cure for can-
cer. By studying how retinoic acid works to cause
remission of acute promylocytic leukemia, a deadly
blood cancer, researchers discovered that when the
gene UBE1L was introduced into leukemic cells, it
killed them in the same way that retinoic acid does.
(See also
ENDOCRINE SYSTEM.)
retinoid See BETA-CAROTENE; VITAMIN A.
retinol See VITAMIN A
.
retinol equivalents (RE) See VITAMIN A.
rheumatoid arthritis (RA) A chronic inflamma-
tory disease of the joints. Rheumatoid arthritis is
characterized by overgrowth of joint tissue leading
to swollen immobilized joints as a result of an over-
active
IMMUNE SYSTEM. Rheumatoid arthritis is clas-
sified as an
AUTOIMMUNE DISEASE in which the
immune system attacks the body by developing
antibodies against joint tissue. An estimated 7 mil-

lion people in the United States are affected by RA.
The much more common ailment,
OSTEOARTHRITIS,
represents a joint “wear and tear” arthritis and does
not involve the immune system, is not an autoim-
mune disease, and its cause is unrelated to
rheumatoid arthritis.
Rheumatoid arthritis can begin in young or
middle-aged adults. The triggering mechanisms are
unproven. It seems likely there are many con-
tributing factors. Infections, allergies, genetic sus-
558 respiratory chain
ceptibility, lifestyle, and nutritional factors may
play a role. There is no cure, although some med-
ications are used to reduce
INFLAMMATION (anti-
inflammatory drugs).
ASPIRIN is the most common
drug used to relieve pain and swelling, but high
doses of aspirin can cause gastrointestinal bleeding,
stomach irritation, even reduced hearing. Newer
anti-inflammatory medicines and less irritating
nonsteroidal anti-inflammatory drugs (NSAIDS)
are now available as prescription drugs. Other
NSAIDS include ibuprofen and indomethicin.
However, NSAIDS in general can cause intestinal
inflammation and increase gut permeability to
potentially harmful substances. Cortisone-related
drugs can relieve inflammation. Long-term use can
lead to disabling side effects. These effects include

suppression of the immune system, bone deminer-
alization, and thinning of skin.
Studies in the 1980s demonstrated that fasting
often reduces symptoms of rheumatoid arthritis,
but pain, swelling, and stiffness return when fast-
ing ends. Preliminary clinical trials suggest that a
gluten-free, vegan diet (no animal protein, no
wheat) for three to five months followed by a lac-
tovegetarian diet (only milk and milk products plus
plant-derived foods) for the rest of the year can sig-
nificantly reduce pain, improve grip strength, and
reduce swelling among patients with rheumatoid
arthritis. Therefore, food sensitivities should be
ruled out.
Imbalanced
PROSTAGLANDINS are linked to
chronic conditions. These derivatives of essential
fatty acids help regulate many physiologic
processes, including inflammation. A growing body
of evidence suggests that diet can influence
prostaglandin levels. Supplemental seed oils con-
taining the polyunsaturated fatty acid
GAMMA
LINOLENIC ACID
, such as BORAGE oil and EVENING
PRIMROSE OIL
can reduce arthritic pain. Gamma
linolenic acid is obtained from the
ESSENTIAL FATTY
ACID

, LINOLEIC ACID, and leads to the formation of a
set of anti-inflammatory prostaglandins. Other
anti-inflammatory prostaglandins are derived from
omega-3 fatty acids that occur in flaxseed oil and
coldwater fish like
SALMON, HERRING, SARDINES, and
fish oils. These fish provide omega-3 fatty acids,
such as
EICOSAPENTAENOIC ACID, and diets rich in
fish can decrease inflammation. Supplemental
omega-3 oils (flaxseed oil and fish oil) may help
decrease symptoms of arthritis.
Among the B vitamins,
PANTOTHENIC ACID in
large amounts has been used to relieve symptoms
of rheumatoid arthritis. Vitamin K may help stabi-
lize joint linings. Free radical and oxidative damage
accompany inflammation, and the diet should pro-
vide ample
ANTIOXIDANTS
: SELENIUM, VITAMIN E, and
VITAMIN C. ZINC, MANGANESE
, and COPPER support
the antioxidant enzyme,
SUPEROXIDE DISMUTASE,
which can protect tissues from free radical damage.
Herbal preparations such as feverfew and
LICORICE
have been used in botanical medicine to treat
rheumatoid arthritis.

FLAVONOIDS such as QUERCETIN
and catechin reduce inflammation by acting as
antioxidants and by inhibiting mast cell degranula-
tion, a major contributor to tissue injury. They also
limit tissue destruction associated with inflamma-
tion. (See also
OSTEOMALACIA; OSTEOPOROSIS.)
Toohey, Cordain L. et al. “Modulation of Immune Func-
tion by Dietary Lectins in Rheumatoid Arthritis,”
British Journal of Nutrition 83, no. 3 (2000): 207–217.
rhubarb (Rheum rhaponticum) A cultivated
perennial with thick, typically red stalks that is
classified as a fruit. Only the leaf stalks of this plant
are edible because roots and leaves contain a
potentially toxic material,
OXALIC ACID. Rhubarb
stalks are cooked in pies, sauces, rhubarb crumble,
and other baked goods, jams, and preserves, and
they can be fermented to produce wine. Rhubarb is
extremely tart and requires the addition of sweet-
eners to make it appetizing. The calcium in rhubarb
is poorly absorbed. Like spinach, it is not a good
dietary source of calcium. Nutrient content of
cooked rhubarb with added sugar (1 cup, 240 g) is:
279 calories; protein, 0.9 g; carbohydrate, 75 g;
fiber, 5.3 g; calcium, 348 mg; vitamin C, 8 mg; thi-
amin, 0.04 mg; riboflavin, 0.06 mg; and niacin,
0.48 mg.
riboflavin (vitamin B
2

) A bright yellow B com-
plex
VITAMIN. This widely distributed vitamin func-
tions in oxidation-reduction reactions. Riboflavin
works together with the B vitamins
THIAMIN,
NIACIN, and PANTOTHENIC ACID to oxidize FAT and
CARBOHYDRATE to carbon dioxide to produce
riboflavin 559
ENERGY. The complete oxidation of these fuels
occurs via the
KREB’S CYCLE, a sequence of enzyme-
catalyzed steps that represents the major energy-
yielding pathway of most tissues. Riboflavin is the
parent of
FLAVIN ADENINE DINUCLEOTIDE (FAD) and
flavin mononucleotide (FMN), two enzyme helpers
(
COENZYMES). Riboflavin participates in the body’s
defense system to oxidize toxins and foreign com-
pounds. It supports glutathione reductase, an
enzyme that replenishes an important cellular
ANTIOXIDANT
called glutathione. This system repre-
sents a major defense against oxidative damage. In
addition, the production of steroid
HORMONES by
the
ADRENAL GLANDS requires riboflavin. More gen-
erally, riboflavin is essential for successful repro-

duction in experimental animals, for healthy skin,
eyes, and nerve function.
Possible Roles in Maintaining Health
Unlike niacin deficiency or thiamin deficiency,
chronic riboflavin deficiency does not cause a dis-
tinctive human disease.
ARIBOFLAVINOSIS, a ribofla-
vin deficiency disease, occurs in association with
deficiencies of other B complex vitamins. Symp-
toms of riboflavin deficiency include
FATIGUE,
delayed wound healing, sore mouth, cracks in the
corners of the mouth, tongue inflammation (
GLOS-
SITIS
), blurred vision and light sensitivity, and
eczema of face and genitalia.
Sources
Riboflavin is widely distributed among foods, but
the levels vary greatly. Rich sources include organ
meats (
LIVER, kidney, and heart); dairy products
(
MILK, CHEESE, YOGURT); and BREWER’S YEAST.
BREAKFAST CEREAL
, enriched flour, almonds, lean
meat, raw mushrooms, wheat bran, enriched corn-
meal, soybean flour, and dark green leafy
VEGETA-
BLES are good sources. Fifty percent of the

riboflavin in milk can be lost within two hours after
exposure to light. Storing milk in cartons rather
than in glass bottles markedly reduces the loss.
Riboflavin is destroyed by light and by heat. Up to
20 percent of riboflavin is lost from milk by evapo-
ration or by
PASTEURIZATION. Raw fruits and vegeta-
bles generally provide little riboflavin.
The U.S. enrichment program for white flour
was initiated in 1941. Since then, riboflavin, as
well as thiamin, niacin, and iron, have been added
to flour and cereal products that together account
for an estimated 0.33 mg of riboflavin per day for a
typical American. Riboflavin is nontoxic; excesses
are excreted and turn urine yellow.
Requirements
The
RECOMMENDED DIETARY ALLOWANCE (RDA) of
riboflavin is 1.7 mg per day for men and 1.3 mg per
day for women between the ages of 25 and 50. The
requirement is somewhat higher for women who
are pregnant or breast-feeding. Anyone with a
severely compromised diet is prone to B complex
vitamin deficiency in general. This includes children
of developing countries who do not eat enough
eggs, meat, and milk or enriched foods; alcoholics;
elderly persons with an imbalanced diet; people on
severe weight loss programs; chronic users of fiber-
based laxatives or tranquilizers; and patients with
HYPOTHYROIDISM. Vigorous EXERCISE also can in-

crease the requirement of riboflavin in women. (See
also
CARBOHYDRATE METABOLISM; FAT METABOLISM.)
rice (Oryza sativa) An important cereal grain and
a food staple in Asia and other parts of the world.
Rice is a grass related to
WHEAT, OATS, and BARLEY.
Rice originated from wild species that persist in
southeast Asia. Rice culture occurred in China by
2200
B.C. and in Thailand by 5000 to 3500 B.C.
Worldwide, China, India, Indonesia, Bangladesh,
and Thailand produce the most rice. In populations
dependent on rice, it can account for 60 percent to
80 percent of total calories. In Asia the average
annual consumption is 200 to 400 pounds (90 to
180 g) per person. Rice consumption in the United
States has been steadily growing in the past two
decades. In 2002 per capita rice consumption in this
country was 26.5 pounds a year. The U.S. produces
1 percent to 2 percent of the world’s crop.
There are many thousands of rice strains,
including strains adapted to warm or cold climates,
low or high elevations. Paddy rice is cultivated in
flooded fields most of the growing season, while
upland rice can grow in wet soil and doesn’t
require flooding. Many hardy strains of rice now
used were products of the
GREEN REVOLUTION,a
concentrated effort of agriculture, science, and

industry to improve crop productivity in develop-
ing nations. Use of these strains, better irrigation,
560 rice
increased use of chemical fertilizers and synthetic
pesticides created a dramatic increase in grain pro-
duction in Asia, South America, and Africa.
Rice is classified according to size: Short-grain
rice is oval in shape, contains less
AMYLOSE
,a
straight-chain form of
STARCH, and is sticky when
cooked. Medium-grain rice is more tender than
long-grain rice and is used to make cold breakfast
cereals. Long-grain rice has a high amylose con-
tent, and its kernels do not stick to each other
when cooked. Long-grain rice accounts for more
than 70 percent of the U.S. domestic production.
Waxy rice cooks to a sticky paste and is used for
cakes and confections. Wild rice, Zizania aquatica, is
native to eastern North America. Though it is an
annual grass, it is a distant cousin of true rice.
White or polished rice is produced by milling to
remove bran, husk, and germ, which reduces the
content of B vitamins. Polished rice is approxi-
mately 92 percent starch and only 2 percent addi-
tional nutrients. Notably, the content of
THIAMIN in
polished rice is only 18 percent of that of husked
rice. Among populations subsisting primarily on

white rice, the thiamin deficiency disease,
BERIBERI
may occur.
In the United States, white rice is enriched with
thiamin,
RIBOFLAVIN, NIACIN, IRON, and CALCIUM.
Removing hulls from dried, rough rice yields
brown rice. Brown rice resembles whole wheat in
nutrient content. The protein content is lower than
wheat but the quality is higher. Nonetheless, rice
protein is deficient in the
AMINO ACID, LYSINE, typi-
cal of most grains. Rice contains more niacin than
does corn. Parboiled rice represents rough rice that
has been soaked, steamed, and dried to loosen
husks, which are removed by milling. Greater
amounts of nutrients are retained than in white
rice. Rice is used as a breakfast food (puffed rice,
flakes, crispies), rice flour, flaked rice, rice-based
baby food, rice oil, and rice bran. Rice bran con-
tains fiber that can help reduce blood cholesterol
levels and rice oil, which also has a cholesterol-
lowering effect. Rice bran does not become sticky
when cooked, unlike oat bran. Rice is commonly
steamed or boiled. The more water used in cooking
rice, the more nutrients are lost.
The nutrient content of 1 cup (205 g) of white,
enriched rice (cooked without salt) is 223 calories;
protein, 4.1 g; carbohydrate, 49.6 g; fiber, 0.82 g;
fat, 0.2 g; iron, 2.9 mg; thiamin, 0.22 mg; ribo-

flavin, 0.02 mg; niacin, 2.05 mg.
rickets A disorder of bone formation in growing
children commonly due to
VITAMIN D deficiency.
Rickets is characterized by softening and deforma-
tion of long
BONES, reflecting an interference with
bone growth and altered mineralization. The bone
disease in adults resulting from vitamin D defi-
ciency is called
OSTEOMALACIA. The mineral portion
of bone consists mainly of
CALCIUM and phosphate;
thus a deficiency of either can cause rickets. Low
calcium can be the result of a dietary deficiency of
calcium or of vitamin D, or a problem with vitamin
D’s activation to the hormone form, calcitriol
(1,25-dihydroxyvitamin D
3
). Some people may be
unable to convert vitamin D to calcitriol because of
a rare genetic defect in the kidney enzyme per-
forming the last step in the activation of vitamin D
to calcitriol. Dietary vitamin D sources include for-
tified
MILK and fish liver oils. (Alternatively, ultra-
violet light converts provitamin D in the skin to
vitamin D; therefore, inadequate exposure to win-
ter sunlight, particularly in populations living in
northern latitudes and in institutionalized people,

can lead to vitamin D deficiency. Still other
problems can be caused by malabsorption syn-
dromes associated with
CELIAC DISEASE and INFLAM-
MATORY BOWEL DISEASE
, which can limit uptake of
fat-soluble vitamins, including vitamin D, even
when dietary intake is normal.
Abnormally low phosphate and calcium in chil-
dren’s diets can also cause rickets. Hormone imbal-
ances, such as an increased secretion of parathyroid
hormone, can trigger calcium and phosphate
release from bone. This loss of mineral softens
bone.
Sometimes rickets accompanies kidney disease
when the kidneys fail to synthesize calcitriol. Other
types of rickets can be caused by genetic abnormal-
ities in tissues so that the hormone, though pre-
sent, cannot perform its physiologic functions. (See
also
OSTEOARTHRITIS; OSTEOPOROSIS; SKELETON.)
risk due to chemicals in food and water The
chance of injury or illness resulting from exposure to
synthetic chemicals in
FOOD. Logical and reasonable
risk due to chemicals in food and water 561
decisions can be made when risks are identified and
their magnitude assessed. In reality, no substance is
absolutely safe and there is no risk-free environ-
ment, although modern technology and policies

based on simple, rapid solutions to public health
problems have nurtured this common expectation.
Risk estimates are averages of populations and
are not designed for individuals. Epidemiology, the
study of populations, has identified several large
risks for chronic diseases. In the United States,
HEART DISEASE
is the number-one killer, accounting
for 40 percent of all deaths (death rate is 265.9 per
100,000 people). Risk increases with age, family
history of heart disease,
OBESITY, high blood pres-
sure, smoking, and excessive fat intake.
CANCER is
the number-two killer, with 25 percent of deaths.
About 77 percent of all cancers are diagnosed in
people who are age 55 or older. According to the
American Cancer Society, one-third of all cancer
deaths in 2002 (about l85,170) were related to
poor nutrition and sedentary lifestyles; about
170,000 cancer deaths were related to tobacco use;
another 19,000 were related to excessive alcohol
use, often in combination with tobacco use.
Stroke is the third leading cause of death, killing
more than 166,000 people annually (60.2 deaths
per 100,000 people).
One problem inherent in assessing cancer risk
is that the delay between exposure to a cancer-
causing agent (
CARCINOGEN) and development of

cancer can be many years. The risk of disease also
depends on an individual’s health history and
genetic predisposition. Deficiencies in primary
health care, which especially affect pregnant
women, fetuses, children, and low-income people,
also increase disease and death risks. Stroke
accounts for 6.9 percent of deaths (death rate of 61
per 100,000). Those at greatest risk are adults over
55, particularly over the age of 65. Risk increases
with age, untreated high blood pressure,
DIABETES,
obesity, and smoking.
Technology has posed questions about the defi-
nition of a safe level of exposure to potentially
harmful agents. Sensitive analytical techniques can
now readily detect traces of contaminants in foods
at levels unattainable in the 1970s. Contaminant
levels at parts per billion and even parts per trillion
can be detected in air, water, foods, and even
human milk. The long-term effects on health of
chronic exposure to such low levels of multiple
contaminants remain unknown.
Under the Food Quality Protection Act of 1996
the EPA is required to consider risks and benefits of
agricultural chemicals. This act created a new
safety standard for pesticides in food: a reasonable
certainty of no harm.
Public perception of risk depends in part on the
source of the risk, whether it is readily apparent,
and the circumstances under which it appeared.

Man-made hazards are less acceptable than natural
(uncontrollable) causes. Perceived risk increases
when there is no clear benefit and when the risk is
unfamiliar. For example, a government agency can
estimate that a pesticide may cause between 1 and
100 deaths per million; this risk may be perceived
as unacceptable by some. On the other hand, traf-
fic accidents kill about 42,000 Americans yearly
(about 110 people a day) which is generally con-
sidered an acceptable modern-day risk.
Each approach to risk assessment presents
strengths and weaknesses. A common experimen-
tal strategy in cancer risk assessment is based on
examining cancer risk for rats and mice exposed to
high levels of an agent in order to detect an observ-
able effect. Applying these data to human popula-
tions involves assumptions that humans will
behave in the same way as animals and assump-
tions that the effects of a low dose can be calculated
from a high dose administered to the animals. Even
more uncertainty is involved if comparisons are
made on the basis of extreme toxicity. On the other
hand, risks calculated in a similar way can be com-
pared; thus the risk of consuming different types of
carcinogens can be compared from historical data.
Exposure to similar compounds can also be used as
a basis of comparison. Risks of cancer due to vari-
ous chlorinated hydrocarbons in chlorinated drink-
ing water can be similarly compared.
Questions to Ask Regarding a Risk

• What is the absolute risk? Is it 1 per 1,000 or 10
per million? A tenfold increase in risk (a state-
ment about relative risk) has different meanings
in terms of the total numbers of people involved
in each of these cases. Thus a tenfold increase in
risk at 1 per 1,000 is 10 per thousand, or 10,000
562 risk due to chemicals in food and water
people per million. A tenfold increase in risk at
10 per million is 100 people per million, mean-
ing that far fewer people will be affected.
• What is the likelihood of exposure? Risk
increases with amount of exposure or dosage
and duration of exposure.
• What are the tradeoffs? For example, is it accept-
able to use a pesticide that lowers food costs sub-
stantially, yet could increase the number of
cancer deaths by one in a million? This would be
an application of a so-called negligible risk stan-
dard. (See also
GENETIC ENGINEERING.)
RNA (ribonucleic acid) The type of biomolecule
that directs the synthesis of
PROTEIN after receiving
information from
DNA. RNA is classified as a
NUCLEIC ACID, the same chemical family as DNA.
Three different types of RNA perform different
functions in protein synthesis. “Messenger-RNA”
represents a copy of the genetic material that car-
ries the code words specifying the amino acid se-

quence characteristic of each protein. “Ribosomal
RNA” occurs in ribosomes, cytoplasmic particles
that combine with messenger RNA and provide the
site of protein synthesis. A third family of RNA is
“transfer RNA,” which carries activated amino
acids to assemble proteins. Transfer RNAs “read”
code words in the messenger RNA, align amino
acids in the proper sequence and permit amino
acids to be joined together. Thus transfer RNAs
help translate the language of DNA into the lan-
guage of proteins in all cells.
In terms of composition, RNA consists of phos-
phate; the simple sugar, ribose; and four nitrogen-
containing compounds (
ADENINE, GUANINE, uracil,
and
CYTOSINE). Three of these bases occur in DNA;
only uracil is unique to RNA. RNA is assembled by
the body from simple nutrients, and there is no
dietary requirement for RNA. The enzyme that
synthesizes RNA (RNA polymerase) requires the
trace mineral nutrient
ZINC for activity. (See also
PURINE; PYRIMIDINE; URIC ACID.)
rosemary (Rosmarinus officinalis) A perennial
evergreen that grows as a shrub. Rosemary has
long, thin leaves with a rich scent. Leaves of this
pungent herb are used dried or fresh as a strong
seasoning for pork, veal, lamb, and chicken. It is
used with tomato sauce, marinades, soups, and

ragouts. Rosemary extracts are used as an antioxi-
dant by the food industry. The herb contains rose-
maricine, which can stimulate the digestive tract,
help with fat digestion and lessen joint pain. It has
been used as an antiseptic mouthwash and gargle.
rotation diet A DIET
plan in which related FOODS
or foods within botanical families are not eaten
more frequently than every four days. Studies of
patients, especially children with food
ALLERGIES,
suggest that rotating foods and eating them in
moderation reduces the tendency to develop new
food allergies or to activate existing sensitivities.
Rotation diets can help reduce the symptoms of
food allergies and to identify problematic foods.
Use of rotation diets also permits the patient to
eliminate many foods. A variety of books are now
available to assist in food selection, menu planning,
and meal preparation. Typically, foods are listed in
four columns representing days one to four and
grouped according to families. Typical categories
include
MEAT, GRAIN, FISH, FRUIT, VEGETABLES, bever-
ages,
NUTS and seeds, NATURAL SWEETENERS, MILK or
milk substitutes, thickeners, and fats and oils.
Foods in one list do not appear in the other lists, in
order to avoid selecting a food more frequently
than every four days.

It is advisable to begin a rotation diet slowly
because this type of diet represents major adjust-
ments. One approach is to begin by rotating
grains/starches by using wheat products on day
one, then rice products on day two, then corn
products on day three, with oats on day four. Grain
alternatives such as
AMARANTH, QUINOA, MILLET,or
BARLEY can be substituted for any of the above
grain groups. After one to two weeks, meats can be
rotated, for example, beef (red meat) on day one,
then turkey (poultry) on day two, then pork (red
meat) on day three, then chicken (poultry) on day
four. Veal, calf liver, venison, and lamb fall within
the beef category because these are related. Simi-
larly, goose and turkey fall in the turkey group, and
pheasant and quail are listed with chicken. To
rotate fruits, the following are options:
CITRUS FRUIT
on day one, followed by the apple/grape family on
day two, then by
MELONS on day three and berries
rotation diet 563
on day four. For vegetables, options can include
CARROTS, BEETS, CHARD, SPINACH, or CELERY on day
one; then the
LEGUMES with PEAS, BEANS, LENTILS or
soy, or the squash family on day two; then night-
shade vegetables, such as
POTATO, EGGPLANT, or

PEPPERS on day three; and the cabbage family with
CAULIFLOWER, BROCCOLI, or BRUSSELS SPROUTS on
day four. Symptoms may improve after several
weeks of diet rotation. Often, it is easier to use a
rotation diet when other family members support
each other in making major dietary changes.
Vatn M. H. et al. “Adverse Reaction to Food: Assessment
by Double-Blind Placebo-Controlled Food Challenge
and Clinical Psychosomatic and Immunologic Analy-
sis,” Digestion 56, (1995): 421–428.
royal jelly A viscous liquid secreted by the sali-
vary glands of “nurse” bees and fed to the bee lar-
vae that will eventually develop into “queen” bees.
Like
BEE POLLEN, royal jelly has been marketed by
food supplement manufacturers as a treatment for
fatigue, digestive disorders, and cardiovascular
problems. No reliable scientific studies support
these claims, and the safety of royal jelly supple-
ments has not been established. Some consumers
have reported suffering allergic reactions.
rutabaga (Brassica napobrassica; Swedish turnip)
A root vegetable that resembles a large
TURNIP. It is
believed to have originated in a hybrid between
KALE and turnip, perhaps in medieval Europe.
Rutabaga is used both as food and as livestock fod-
der. In the United States, it is grown mainly in the
northern states. Unlike turnip greens, rutabaga
leaves are not edible. The root can be baked, boiled,

and mashed with potatoes, served in souffles,
casseroles, stews, and soups.
Turnips and rutabagas contain small amounts of
GOITROGENS, substances that block IODINE uptake.
The effects of these materials can be worsened by
an iodine-deficient diet and when large quantities
are eaten, not a usual situation in the United
States. Rutabagas are a rich source of vitamin C.
The nutrient content of 1 cup (140 g) of rutabagas
is: 64 calories; protein, 1.5 g; carbohydrate, 15.4 g;
fiber, 1.4 g; fat, 0.28 g; vitamin A, 810 IU; vitamin
C, 60 mg; thiamin, 0.1 mg; riboflavin, 0.1 mg;
niacin, 0.14 mg.
rye (Secale cereale) A common cereal grain
related to wheat. Rye was domesticated in north-
ern Europe in the fourth century
B.C., and inde-
pendently in Asia and the Middle East. In medieval
Europe rye became a staple bread grain. Rye flour
is second only to wheat flour in terms of worldwide
popularity for bread making, although it accounts
for only 3 percent of the worldwide production of
cereal grains and ranks eighth in the world. North-
ern Europe remains a major region for rye produc-
tion. Popularity in the United States has declined
steadily since 1920, and the United States produces
2 percent of the world rye crop. Ergot, a fungus
that produces a poisonous substance that can cause
convulsions, can infect rye. Limits have been estab-
lished for ergot contamination.

Rye berries (groats), representing the husked
whole grain, can be cooked like
RICE. Whole rye
flour is dark and contains most of the nutrients of
rye berries. Light rye flour is a refined product,
containing relatively more starch and less germ; it
may be bleached. Bleached rye flour is less nutri-
tious than dark flour. Cracked rye is crushed rye
berries. It can be cooked like cracked wheat or
OATS, as a BREAKFAST CEREAL. Rolled rye flakes are
produced by heating rye berries until soft, and flat-
tening them with steel rollers. Rye is used to pro-
duce crackers and rye flakes are used as a
hamburger extender. Rye is also sprouted and
served as a salad green. Rye is fermented to make
whiskey.
Authentic rye bread is dense with a robust fla-
vor. It is less responsive to yeast as a leavening
agent; consequently, wheat flour is often added to
improve dough-rising properties. Rye bread pre-
pared with wheat flour may contain artificial col-
oring or other coloring to darken it. The nutrient
value of rye is similar to wheat. Rye protein, like
wheat protein, is deficient in the essential amino
acid
LYSINE. Rye flour (1 cup, dark) provides 419
calories; protein, 20.9 g; carbohydrate, 87.2 g; fiber,
3.1 g; fat, 3.3 g; calcium, 69 mg; sodium, 1 mg; thi-
amin, 0.78 mg; riboflavin, 0.28 mg; niacin, 3.5 mg.
564 royal jelly