Trace Minerals

Iron

  • Sources of Iron:

    • Heme Iron: Found in animal products (e.g. meat, poultry, seafood).
    • Non-Heme Iron: Found in plant foods (e.g. whole grains, nuts, seeds, legumes, leafy greens).

  • Iron Needs:

    • RDA: 18 mg/day for adult women, 8 mg/day for adult men.
    • After menopause, women's RDA drops to 8 mg/day.
    • Average North American Intake: 12-17 mg/day.

  • Food Examples and Iron Content:

    • Beef roast (3 oz): significant source
    • Sesame seeds (2 tbsp): good source
    • Navy beans (1 cup): high in non-heme iron
    • Liverwurst (3 oz): very high source
    • Clams (3 oz): highest source
    • Spinach (cooked, 1/2 cup): contains non-heme iron but poor absorption

Iron Absorption, Transportation, and Excretion

  • Iron Proteins:

    • Ferritin: Stores iron.
    • Transferrin: Transports iron within the blood.
    • Hemosiderin: Another storage form of iron.

  • Absorption Process:

    • Iron is absorbed in the small intestine and transported via transferrin to the liver for storage.
    • Bile helps eliminate approximately 10% of Fe intake.

  • Factors Affecting Iron Absorption:

    • Increase: high body demand, low iron stores, heme iron, meat protein, vitamin C intake, and gastric acidity.
    • Decrease: low need for iron, presence of phytic acid, oxalic acid, polyphenols, reduced gastric acidity, and excessive intake of other minerals (zinc, calcium).

Functions of Iron

  • Roles:
    • Integral in redox reactions and a component of hemoglobin and myoglobin.
    • Acts as a cofactor for various enzymes involved in energy metabolism and drug metabolism in the liver.

Iron Deficiency, Overload, and Toxicity

  • Deficiency:

    • Iron deficiency is the most widespread mineral deficiency worldwide, leading to iron deficiency anemia.
    • High-risk groups: premature infants, young children, females of childbearing age, vegetarians.

  • Overload and Toxicity:

    • UL: 45 mg/day.
    • Risks of accidental overdose in children and conditions like Hemochromatosis (excess iron absorption).

  • Stages of Iron Deficiency:

    • Early: marginal deficiency, low intake, increased iron losses.
    • Moderate: depleted iron stores with no apparent symptoms.
    • Severe: anemia, reduced exercise capacity, immune function impact, cognitive development issues in children.

Zinc

  • Sources:

    • Found in protein-rich foods (e.g. meat, seafood, nuts, beans, whole grains).

  • Needs:

    • RDA: 11 mg/d for adult men, 8 mg/d for adult women; DV: 15 mg.

  • Absorption:

    • Occurs in the small intestine and is influenced by dietary composition.
    • Iron competes with zinc for absorption.

  • Functions:

    • Supports over 300 enzymes, critical for DNA/RNA synthesis, immune function, and wound healing.

  • Deficiency and Toxicity:

    • Deficiency leads to common overt symptoms; UL is 40 mg/day.

Copper

  • Sources:

    • Liver, shellfish, nuts, seeds, lentils, soy, dark chocolate.

  • Needs:

    • RDA: 900 µg/daily, with an average intake of 1000 – 1600 µg.

  • Functions:

    • Critical in enzyme systems, such as superoxide dismutase which prevents oxidative damage.

  • Deficiency and Toxicity:

    • Rare, seen in specific conditions; UL: 10 mg/day.

Manganese

  • Sources:

    • Whole grains, nuts, legumes, leafy greens, tea.

  • Needs:

    • AI: 2.3 mg/d for adult men, 1.8 mg/d for adult women.

  • Functions:

    • Involved in carbohydrate metabolism, antioxidant systems, and collagen formation.

  • Deficiency and Toxicity:

    • Rare, with UL: 11 mg/day.

Iodine

  • Sources:

    • Saltwater seafood, iodized salt, dairy. Goitrogens can inhibit its absorption.

  • Needs:

    • RDA: 150 µg/d; average intake is 190-300 µg.

  • Functions:

    • Essential for thyroid hormone synthesis (T3 and T4).

  • Deficiency and Toxicity:

    • Deficiency leads to IDDs like goiter; UL: 100 µg/d.

Selenium

  • Sources:

    • Varies by soil content; includes seafood, meats, cereals, and grains.

  • Needs:

    • RDA: 55 µg.

  • Functions:

    • Acts as an antioxidant, part of several critical enzyme systems.

  • Deficiency and Toxicity:

    • Associated with Keshan disease; UL is 400 µg/d.

Chromium

  • Sources:

    • Found in processed meats, liver, eggs, whole grains, broccoli.

  • Needs:

    • AI: 35 µg/m for men under 50, 25 µg for women under 50.

  • Functions:

    • Enhances insulin function and glucose uptake; however, evidence for efficacy in Type II diabetes is inconclusive.

  • Deficiency and Toxicity:

    • Results in weight loss and glucose intolerance; no established UL.

Fluoride

  • Sources:

    • Fluoridated water, tea, seafood.

  • Needs:

    • AI: 3 mg/d for women, 4 mg/d for men; UL: varies by age.

  • Functions:

    • Strengthens teeth and bones; deficiency causes increased risk of dental caries.

  • Toxicity:

    • Can cause nausea and potentially fatal symptoms with overconsumption.

Molybdenum and Ultra Trace Minerals

  • Molybdenum:

    • RDA: 45 µg/d; UL: 2000 µg/d.
    • Functions as a cofactor in enzymatic reactions.

  • Ultratrace Minerals (like arsenic, boron, nickel):

    • Proposed functions involve various biochemical roles but are not well characterized.

Nutrients, Diet, and Cancer

  • Cancer Definition: Tumors can be benign or malignant, and they can metastasize.

  • Carcinogenesis Steps:

    1. Exposure to carcinogens.
    2. Promotion of altered cells.
    3. Progression to cancer growth.

  • Dietary Impact on Cancer:

    • Important factors include consumption of fruits, vegetables, energy intake, and certain vitamins like D and calcium.

  • Guidelines for Cancer Prevention:

    1. Emphasize plant-based foods.
    2. Increase vegetable and fruit intake.
    3. Maintain a healthy weight and stay active.
    4. Moderation in alcohol consumption.
    5. Limit fat and salt intake.
    6. Ensure food safety, and avoid tobacco usage.