Transcript Iron

Chapter 12 Lecture
The Science of Nutrition
Third Edition
Nutrients Involved
in Blood Health and
Immunity
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Blood
• Functions
– Transports nutrients and oxygen to cells
– Removes waste products generated from
metabolism
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Components of Blood
• 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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© 2014 Pearson Education, Inc.
Minerals That Maintain Healthy Blood
• Iron
• Zinc
• Copper
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© 2014 Pearson Education, Inc.
Iron
• Iron is a trace mineral
• Component of oxygen-carrying hemoglobin and
myoglobin (muscle)
• Component of cytochromes, electron carriers
within the metabolic pathways for energy
production from carbohydrates, fats, and protein
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© 2014 Pearson Education, Inc.
Maintaining Iron Homeostasis
• Regulation of iron digestion, absorption,
transport, storage, and excretion
• Factors that alter iron digestion and absorption
– 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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© 2014 Pearson Education, Inc.
Iron
• Two types of iron in foods
– Heme iron—found only in animal-based
foods and more absorbable
– Non-heme iron—not as easily absorbed
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Iron
• Factors that promote iron absorption
– Meat factor
– Stomach acids
– Vitamin C
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Iron
• Factors that impair iron absorption
– 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
• Iron transport
– Transferrin: iron-transport protein in blood
– Receptors on cells transport iron into cells
• Iron storage
– Ferritin and hemosiderin help meet iron needs
– Liver, bone marrow, and spleen
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Iron
• Regulation of total-body iron:
– Iron absorption
– Iron losses
– Storage and recycling of iron
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Iron
• Recommended intake
– 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
– Meat, poultry, fish, clams, oysters, liver,
enriched or fortified cereals and breads
– Supplements
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© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Too Much Iron
• 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
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Not Enough Iron
• Most common nutrient deficiency in the world
• High risk: infants, young children, adolescent
girls, premenopausal and pregnant women
• 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
1. Iron depletion is caused by a decrease in iron
stores
2. Iron-deficiency erythropoiesis occurs with
decreased iron transport
3. Iron-deficiency anemia results in reduced
normal, healthy red blood cell production,
decreased size, inadequate hemoglobin
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© 2014 Pearson Education, Inc.
Zinc
• Zinc is a trace mineral
• Functions of zinc
– Component of enzymes (heme synthesis)
– Maintain structural integrity and shape of
proteins
– Assist in regulating gene expression
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© 2014 Pearson Education, Inc.
Zinc
• Absorption increases with need: growth, sexual
development, pregnancy
• Dietary factors inhibit zinc absorption
– High non-heme iron intake
– Phytates and fiber (whole grains, beans)
• Dietary factor enhances zinc absorption
– Animal-based protein
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Zinc
• RDA: 8 mg/day for women, 11 mg/day for men
• Sources of zinc
– Red meats, some seafood, whole grains,
enriched grains and cereals
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© 2014 Pearson Education, Inc.
Zinc
• Too much zinc
– Toxicity can occur from supplements
– Symptoms: intestinal pain, cramps, nausea,
vomiting
– Depressed immune function
– Decreased high-density lipoprotein
concentrations
– Interference with copper and iron absorption.
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Zinc
• Not enough zinc
– Deficiencies are uncommon in the United
States
– Symptoms: growth retardation, diarrhea,
delayed sexual maturation, hair loss, impaired
appetite, infections
– Lack of good assessment parameters for zinc
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Copper
• Copper is a trace mineral
• Functions of copper
– Required for iron transport
– Cofactor in energy metabolism and for
connective tissue production
– Part of superoxide dismutase antioxidant
enzyme system
– Regulates neurotransmitters (serotonin)
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Copper
• Factors that promote copper absorption
– More copper is absorbed with low-copper diet
• Factors that impair copper absorption
– High zinc intakes
– High iron intakes
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Copper
• Recommended intake
– RDA for adults is 900 µg/day
• Sources of copper
– Organ meats, seafood, nuts, seeds, wholegrain foods
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© 2014 Pearson Education, Inc.
Copper
• Too much copper
– Toxicity is not well studied in humans
– Symptoms: abdominal pain, nausea, diarrhea,
vomiting, liver damage (Wilson disease)
• Not enough copper
– Copper deficiency is rare
– Symptoms: anemia, reduced white blood
cells, osteoporosis (children—bone
demineralization)
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Vitamins That Maintain Healthy Blood
• Vitamin K
• Folate
• Vitamin B12
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Vitamin K
• Vitamin K is a fat-soluble vitamin important for
both bone and blood health
• Function of vitamin K
– Coenzyme assists in synthesizing blood
coagulating proteins: prothrombin and
procoagulants, factors VII, IX, and X
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Vitamin K
• Factors that promote vitamin K absorption
– Gastrointestinal bacteria produce vitamin K
– Dietary need depends on intestinal health
• Factors that impair vitamin K absorption
– Impaired dietary fat absorption
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Vitamin K
• Recommended intake
– AI for adults is 90 µg/day for women;120
µg/day for men
– No established UL at this time
• Sources of vitamin K
– Green leafy vegetables, such as collard
greens, kale, spinach, cabbage
– Soybean and canola oils
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Vitamin K
• Too much vitamin K
– No known side effects
• Not enough vitamin K
– Deficiency is rare
– Blood fails to clot, bleeding, hemorrhaging
– Fat malabsorption
– Newborns lack intestinal bacteria to produce
vitamin K (injection at birth)
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Folate
• Folate is a water-soluble vitamin
• Functions of folate (coenzyme)
– DNA synthesis, amino acid metabolism
– Cellular division and differentiation
– Functions with B12 and B6 metabolism
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Folate
• Factors that alter folate digestion, absorption,
and balance
– Bioavailability depends on its source: better
from supplements than from food
– Alterations in folate status mimic those of iron
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Folate
• Four states of folate deficiency:
1) Negative folate balance (stage I)
2) Folate depletion (stage II)
3) Folate deficiency erythropoiesis (stage III)
4) Folate deficiency anemia (stage IV)
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Folate
• Recommended intake
– RDA : 400 µg/day adults, 600 µg/day during
pregnancy
• Sources of folate
– Fortification to minimize birth defects:
enriched breads, flours, pasta, grain products
– Liver, spinach, lentils, oatmeal, asparagus
– Heat-sensitive; leached out in cooking liquid
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Folate
• Folate's role in neural tube defects (NTDs)
– Need for folate increases during pregnancy
– NTDs = most common malformations of the
CNS during embryonic and fetal development
– Most common NTD is spina bifida
– Biggest challenge: NTDs occur early in
pregnancy, sometimes before the pregnancy
is known
– Hence, adequate folate intake is important for
sexually active women of childbearing age
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Folate
• Folate's role in macrocytic anemia
– Macrocytic anemias = larger than normal red
blood cells that inhibit adequate oxygen
transport
– Symptoms include fatigue, irritability, difficulty
concentrating, headaches, shortness of
breath, reduced capacity for work
– Similar symptoms can result from vitamin B12
deficiency, so it's important to distinguish the
cause
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Folate
• Too much folate
– Toxicity can result from supplements
– Toxicity can mask vitamin B12 deficiency
– Symptoms: intestinal pain, nausea, vomiting
• Not enough folate
– Macrocytic anemia
– Elevated homocysteine
– Neural tube defects
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Vitamin B12 (Cyanocobalamin)
• Vitamin B12 is a water-soluble vitamin
• Functions of vitamin B12
– Coenzyme for DNA synthesis
– Maintains myelin sheath of nerve fibers
– Metabolism of amino acid homocysteine
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Vitamin B12
• Factors that alter vitamin B12 digestion,
absorption, and balance
– Requires acidic environment (stomach) and
protein intrinsic factor for absorption
– Stored in the liver
– Four levels of vitamin B12 deficiency
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Vitamin B12
• Recommended intake
– RDA for adults is 2.4 µg/day
• Sources of vitamin B12
– Found primarily in dairy products, eggs,
meats, poultry, fish, and shellfish (animal
sources)
– Vegan diet may obtain vitamin B12 from
fortified foods, supplements, or injections
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Vitamin B12
• Too much vitamin B12
– No known adverse effects
• Not enough vitamin B12
– Deficiency is rare, but associated with dietary
insufficiency or reduced absorption
– Gastrointestinal and neurologic effects
– Pernicious anemia (lack intrinsic factor)
– Macrocytic anemia
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Immune System
• A healthy immune system ...
– Protects the body from infectious diseases
– Helps heal wounds
– Guards against the development of cancers
• How does it function?
– Nonspecific immune function
– Specific immune function
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Nonspecific Immune System
• Body's primary defense against microbes,
airborne particles, venom, ingested toxins
• Also called innate immunity
• Intact skin and healthy mucous membranes
• Stomach acid destroys food-borne bacteria
• Inflammatory response causes discomfort, loss
of appetite, fatigue, and fever
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• A macrophage is a type of nonspecific immune
cell. The one shown here is about to engulf an
invading microbe.
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Specific Immune System
• Directed against recognized antigens
• Induces antibodies to destroy invader
– Memory cells remain in circulation
– Two main types of cells: B cells and T cells
• Acquiring specific immunity
– Have disease or vaccinations (immunizations)
– Maternal antibodies
– Antiserum injection (snakebite)
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Immune System
• Malfunction causes chronic inflammation and
infection
– Allergic reactions
– Autoimmune response
– Common in malnourished
– Immune deficiency diseases
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Nutrition and the Immune System
• A nourishing diet provides all the nutrients the
immune system needs
• Single-nutrient subclinical deficiencies can
cause subtle abnormalities in immunity
• Protein-energy malnutrition and severe
micronutrient deficiencies reduce immune
function
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Protein-Energy Malnutrition
• Malnutrition increases the risk for infection
• Infection depresses appetite and often causes
vomiting and diarrhea
• Decreased appetite, vomiting, and diarrhea
cause malnutrition, which increases vulnerability
to infection
• Decreased immunocompetence is a sensitive
indicator of reduced nutritional status
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Obesity
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Increases incidence of infections
Delays wound healing
Poor antibody response to vaccination
Inflammatory state may increase asthma,
hypertension, cardiovascular disease, and type
2 diabetes among obese individuals
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Essential Fatty Acids
• Essential fatty acids are precursors for signaling
molecules eicosanoids
• Omega-6 fatty acids promote inflammatory
response to help contain infection
• Omega-3 fatty acids diminish inflammation in
blood vessels (prevent heart disease)
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Vitamins and Minerals
• Vitamin A maintains mucosal surface
• Vitamins C and E protect cell membrane from
reactive oxygen species
• Zinc assists immune cell gene expression and
enzyme activation (B and T cell proliferation)
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Vitamins and Minerals
• Copper: growth factor for immune cells
• Iron deficiency impairs immune function
• Selenium:
– Coenzyme for glutathione peroxidase
– Promotes B and T cell proliferation
– Antibody production
• Excessive amounts can impair immunity
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