The science of nutrition 4th edition thompson manore vaughan chapter 12
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Chapter 12 Lecture
Chapter 12:
Nutrients Involved in Blood
Health and Immunity
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Blood
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Functions
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Transports nutrients and oxygen to cells
Removes waste products generated from metabolism
Immune function (white blood cells)
Mechanism for heat transfer
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Components of Blood
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Erythrocytes: red blood cells transport oxygen through the body
Leukocytes: white blood cells are key to our immune system
Platelets: cell fragments assist in blood clotting
Plasma: fluid portion of the blood maintains adequate blood volume
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© 2017 Pearson Education, Inc.
Micronutrients That Maintain Healthy Blood
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Minerals
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Iron
Zinc
Copper
Vitamins
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Vitamin K
Vitamin B6
Folate
Vitamin B12
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Iron
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Iron is a trace mineral
Component of oxygen-carrying hemoglobin in erythrocytes and myoglobin in
muscles
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Heme groups depend on iron to carry oxygen in hemoglobin
Component of cytochromes, electron carriers within the metabolic pathways for
energy production from macronutrients
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Part of antioxidant enzyme system
DNA synthesis and cognitive development
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© 2017 Pearson Education, Inc.
Maintaining Iron Homeostasis
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Regulation of iron digestion, absorption, transport, storage, and excretion
Factors that alter iron digestion and absorption
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Individual's iron status
Level of dietary iron consumption
Type of iron in foods
Amount of stomach acid for digestion
Dietary factors enhance or inhibit absorption
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Iron
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Two types of iron in foods
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Heme iron: part of hemoglobin and myoglobin, found only in animal-based
foods and more absorbable
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Non-heme iron: found in both plant and animals, not as easily absorbed
Majority of iron in food (90–95%) is nonheme iron
Iron in animal-based food is 50–60% heme iron
Iron (cont.)
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Factors that enhance iron absorption
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Meat factor
Stomach acids
Vitamin C
Iron (cont.)
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Factors that impair iron absorption
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Phytate (legumes, rice, and whole grains)
Polyphenols (oregano, red wine, tea, coffee)
Vegetable proteins
Fiber
Calcium
Bioavailability of iron from vegan diet is approx. 1–10%, vs. typical Western diet's
absorption of 14–18%
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Iron (cont.)
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Iron transport
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Ferroportin: transports iron and regulates intestinal absorption and release
Transferrin: iron-transport protein in blood
Receptors on cells transport iron into cells
Iron storage
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Ferritin (primary) and hemosiderin (overflow) help meet iron needs
Liver, bone marrow, and spleen
Regulation of Total Body Iron
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Absorption depends on:
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Amount needed
Dietary factors affecting absorption
Losses
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Amount consumed
Major loss in turnover of gut enterocytes
Lost in feces, menses, blood donations
Storage and recycling
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As cells break down, iron is recycled and returned to body's iron pool
Iron (cont.)
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Recommended intake
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RDA varies based on age and gender
8 mg/day for adult men
18 mg/day for adult women,19−50 years
27 mg/day for pregnant women
Sources of iron
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Meat, poultry, fish, clams, oysters, liver, enriched or fortified cereals and
breads
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Supplements
© 2017 Pearson Education, Inc.
© 2017 Pearson Education, Inc.
Too Much Iron
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Accidental iron overdose: most common cause of poisoning deaths in children
Symptoms: nausea, vomiting, diarrhea
Hemochromatosis: excessive absorption of dietary iron and altered iron storage
Treatment: reduce dietary iron, avoid high vitamin C intake, blood removal,
chelation drugs
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Not Enough Iron
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Most common nutrient deficiency in the world
High risk: infants, young children, adolescent girls, premenopausal and pregnant
women
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Poor dietary intakes
Iron losses in blood and sweat
Diets high in fiber or phytates that bind iron
Low stomach acid
Poor iron absorption: poor gut health or dietary supplements with high mineral
levels (e.g., calcium)
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Stages of Iron Deficiency
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Iron depletion (stage I) is caused by a decrease in iron stores
Iron-deficiency erythropoiesis (stage II) occurs with decreased iron transport
Iron-deficiency anemia (stage III) results in reduced normal, healthy red blood cell
production, decreased size, inadequate hemoglobin
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© 2017 Pearson Education, Inc.
Zinc
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Zinc is a trace mineral
Functions of zinc
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Component of enzymes (heme synthesis)
Maintain structural integrity and shape of proteins (zinc fingers)
Assist in regulating gene expression
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Zinc (cont.)
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Metallothionein regulates absorption and release
Absorption increases with need: growth, sexual development, pregnancy
Dietary factors inhibit zinc absorption
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High non-heme iron intake
Phytates and fiber (whole grains, beans)
Dietary factor enhances zinc absorption
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Animal-based protein
