Biology Chapter on Iron

Iron

• Forms:

  • Ferrous (Fe++): Reduced form
  • Ferric (Fe+++): Oxidized form

• Roles in the Body:

  • Cofactor in oxidation-reduction reactions
  • Part of hemoglobin, carrying oxygen in the blood
  • Part of myoglobin, making oxygen available for muscle contractions
  • Utilization of energy in cell metabolism

• Iron Absorption:

  • Excess iron is stored in mucosal ferritin (storage protein)
  • If needed, iron is released from mucosal ferritin to mucosal transferrin (transport protein)
  • Transferrin transports iron to the rest of the body, if not needed, it is excreted in shed intestinal cells

• Iron in Food:

  • Heme iron: Animal source, high bioavailability, not affected by dietary factors
  • Nonheme iron: Animal and plant sources, bioavailability affected by dietary factors

• Factors Enhancing Nonheme Iron Absorption:

  • MFP factor (peptide release during meat, fish, and poultry digestion)
  • Vitamin C
  • Citric acid
  • Lactic acid
  • HCI from stomach
  • Sugars

• Factors Inhibiting Nonheme Iron Absorption:

  • Phytates
  • Fibers
  • Oxalates
  • Calcium and Phosphorus in milk
  • Tannic acid
  • EDTA (Ethylenediaminetetraacetic acid)

• Iron: Heme vs. Nonheme:

  • Heme iron accounts for about 10% of daily intake, but is absorbed well (about 25%)
  • Nonheme iron accounts for the remaining 90% but is less well absorbed (about 17%)
  • All iron in plant-derived foods is nonheme iron.

• Iron Transport and Recycling:

  • Iron is transported in blood by transferrin
  • Liver and spleen dismantle red blood cells, release iron into transferrin, and store excess iron in ferritin and hemosiderin
  • Bone marrow incorporates iron into hemoglobin of red blood cells
  • Iron-containing hemoglobin in red blood cells carries oxygen, some iron is delivered to myoglobin in muscle cells

• Significant Sources of Iron:

  • Red meats, fish, poultry, shellfish, eggs
  • Legumes, dried fruits

• RDA for Iron:

  • Men: 8 mg/day
  • Women (19-50 years): 18 mg/day
  • Women (51+ years): 8 mg/day

• High Risk for Iron Deficiency:

  • Women in their reproductive years
  • Pregnant women
  • Infants and young children
  • Teenagers

• Stages of Iron Deficiency and Assessment Tools:

  • Stage 1: Iron stores diminish (measure serum ferritin)
  • Stage 2: Transport iron decreases (measure transferrin saturation)
  • Stage 3: Hemoglobin production declines (Hemoglobin and hematocrit tests)

• Iron Deficiency and Anemia:

  • Iron deficiency depletes iron stores
  • Iron-deficiency anemia is the severe depletion of iron stores, also known as microcytic hypochromic anemia
  • Symptoms include fatigue, weakness, headaches, apathy, pallor, and poor resistance to cold temperatures

• Iron Deficiency and Behavior:

  • Energy metabolism is impaired
  • Neurotransmitter synthesis is reduced
  • Physical work capacity is reduced
  • Mental productivity is reduced

• Iron Deficiency and Pica:

  • Habit of eating ice, clay, paste, and other nonfood substances
  • Generally in women and children from low-income groups

• Iron Toxicity (Iron Overload):

  • Known as Hemochromatosis, a genetic disorder that enhances iron absorption
  • Repeated blood transfusions
  • Massive doses of supplemental iron
  • May cause hemosiderosis
  • Symptoms include apathy, lethargy, and fatigue

Zinc

• Roles in the Body:

  • Supports the work of metalloenzymes
  • Helps make DNA and RNA, heme for hemoglobin
  • Assists in essential fatty acid metabolism, releases Vitamin A from liver stores
  • Metabolizes carbohydrates
  • Synthesizes proteins
  • Affects platelets in blood clotting and wound healing, thyroid hormone function
  • Influences behavior and learning performance
  • Taste perception
  • Sperm development
  • Fetal development

• Zinc Absorption:

  • Rate of absorption depends on zinc status
  • Phytates and fiber bind zinc and reduce absorption

• Significant Sources:

  • Protein-containing foods
  • Red meats, shellfish
  • Whole grains

• RDA for Zinc:

  • Men: 11 mg/day
  • Women: 8 mg/day

• Deficiency Symptoms:

  • Growth retardation
  • Delayed sexual maturation
  • Impaired immune function
  • Hair loss
  • Eye and skin lesions
  • Loss of appetite

• Toxicity Symptoms:

  • Loss of appetite
  • Impaired immunity
  • Copper and iron deficiencies

Iodine

• Iodine Roles in the Body:

  • Component of two thyroid hormones
  • Regulates growth, development, and metabolic rate

• Iodine Deficiency:

  • Simple goiter: Enlargement of the thyroid gland due to iodine deficiency
  • Goiter: Enlargement of the thyroid gland due to dysfunction or excessive consumption of goitrogens
  • Cretinism: Congenital disease characterized by mental and physical retardation, often caused by maternal iodine deficiency during pregnancy

• Iodine Toxicity:

  • Symptoms include an underactive thyroid gland and goiter

• RDA for Iodine:

  • 150 µg/day for adults

• Sources of Iodine:

  • Iodized salt
  • Seafood
  • Bread and dairy products
  • Plants grown in iodine-rich soils
  • Animals that feed on plants from iodine-rich soils

Other Trace Minerals (Copper)

• Roles in the Body:

  • Part of several enzymes
  • Some copper-containing enzymes are antioxidants

• Deficiency:

  • Deficiency symptoms include anemia and bone abnormalities
  • Menkes disease

• Toxicity:

  • Wilson's disease

• RDA for Copper:

  • 900 µg/day for adults

• Sources of Copper:

  • Seafood
  • Nuts
  • Seeds
  • Legumes
  • Whole grains

Other Trace Minerals (Fluoride)

• Roles in the Body:

  • Formation of teeth and bones
  • Helps make teeth resistant to decay

• Deficiency:

  • Tooth decay

• Toxicity:

  • Tooth damage (fluorosis)

• RDA for Fluoride:

  • 4 mg/day for men
  • 3 mg/day for women

• Sources:

  • Fluoridated drinking water
  • Seafood
  • Tea

Other Trace Minerals (Chromium)

• Roles in the Body:

  • Enhances insulin action; glucose tolerance factors (GTF) are small organic compounds that enhance insulin's action

• RDA for Chromium:

  • 35 µg/day for men
  • 25 µg/day for women

• Sources:

  • Meat
  • Liver
  • Whole grains
  • Brewer's yeast

Contaminant Minerals (Heavy Metals)

• Contaminant Minerals (Heavy Metals):
  • Mercury, lead, and cadmium contaminate food and water
  • These metals disrupt body processes and impair nutrition status.
  • Symptoms in Children (Lead Toxicity):
    • Learning disabilities (reduced short-term memory and impaired concentration)
    • Low IQ
    • Behavioral problems
    • Slow growth
    • Iron-deficiency anemia
    • Dental caries
    • Sleep disturbances
    • Nervous system disorders (seizures)
    • Slow reaction time, poor coordination
    • Impaired hearing
  • Symptoms in Adults (Lead Toxicity):
    • Hypertension
    • Reproductive complications
    • Kidney failure

This quiz explores the various forms of iron, its essential roles in the human body, and the mechanisms of absorption and storage. It also highlights dietary sources of iron and factors that enhance nonheme iron absorption. Test your knowledge on this vital nutrient's biological significance and nutritional aspects.