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Chapter 13


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  • 1. Chapter 13 Trace Minerals
  • 2. Characteristics of this Group of Nutrients A. Each has range of safe & adequate intake B. Required in very small quantities which makes measuring presence in food & body difficult C. Body maintains balance mainly by absorption. Does not excrete trace minerals well D. Variable bioavailability E. Deficiency may be caused by geographic location in addition to poor diet
  • 3. I. Iron (Fe) A. In the Body 1. Exists in two ionic states a. Ferrous  reduced form, has 2 positive charges (Fe+2) b. Ferric  oxidized form, has 3 positive charges (Fe+3) c. Forms important in oxidation-reduction reactions (TCA & ETC)
  • 4. Fe in the Body (cont) 2. Functions a. Oxidation-reduction reactions of energy metabolism b. Structural/functional component of hemoglobin (blood) and myoglobin (muscle) 1. carries oxygen
  • 5. B. Iron Absorption and Metabolism 1. Heme and Nonheme Iron a. Heme iron  meat, fish and poultry and is better absorbed (23%) (hemoglobin) b. Nonheme iron  plant foods as well as animal foods and is absorbed poorly 2. Absorption-enhancing factors a. MFP factor  nonheme iron 1. Consume meat source with nonheme Fe b. Ascorbic Acid (vit. C)  nonheme iron, at same meal
  • 6. Heme and Non-heme Iron in Foods
  • 7. Heme and Non-heme Iron in Foods
  • 8. Iron Absorption and Metabolism (cont) 3. Absorption inhibitors a. phytates and fibers b. calcium and phosphorus c. EDTA in food additives d. tannic acid (tea) e. polyphenols (tea & coffee)
  • 9. Iron Absorption and Metabolism (cont) 4. Mucosal Transferrin  intestinal cell protein which holds absorbed Fe 5. Blood Transferrin  transport protein which carries Fe in blood a. storage in bone marrow, spleen, and liver b. ferritin and hemosiderin = storage proteins c. iron recycling very efficient 1. lose little iron/day - blood losses 2. recycle iron back to bone marrow
  • 10. Iron Absorption and Metabolism (cont) 6. Fe balance controlled at point of absorption a. Intestinal cell (mucosal ferritin) 7. Average absorption of Fe is ~ 10% on mixed diet
  • 11. Iron Routes in the Body
  • 12. C. Iron Deficiency 1. Iron deficiency- initial stages ferritin levels decrease, transferrin increases 2. Iron deficiency w/o anemia a. ‘Tired tissues’ 1. enzymes don’t perform efficiently 3. Iron deficiency w/ anemia a. Severe depletion of Fe stores b. Low hemoglobin concentrations c. Microcytic, hypochromic anemia
  • 13. Iron Deficiency Anemia
  • 14. Iron Deficiency (cont) 4. Prevalence of iron deficiency a. Most common nutrient deficiency in U.S. b. Young children & women susceptible 5. Iron deficiency and behavior a. Decreased physical work b. Unmotivated and apathetic c. Restlessness d. Poor cold tolerance e. Pale appearance, headache fatigue w/anemia f. Pica
  • 15. D. Iron Toxicity 1. Iron overload a. Genetic problem - more common in men 1. Intestine over-absorbs iron 2. Effects: tissue damage due to increased Fe a. Hemochromatosis 1. 8 Fe in tissues  damage b. Hemosiderosis 1. 8 Fe in liver  damage
  • 16. Iron Toxicity (cont) 3. heart disease 4. Arthritis 5. increased infections due to more Fe available to microorganisms b. Overuse of vitamin C and Fe supplements 2. Iron poisoning a. Massive amounts can cause death b. One of the leading causes of death and poisoning in children
  • 17. E. Iron Recommendations and Intakes 1. RDA  men = 10 mg/day 2. RDA  women (child-bearing age) = 15 mg/day Why is the requirement higher for women? 3. Diet overall a. Only contains about 6-7 mg Fe/1000 kcal 1. Fe not much of a problem for men 2. Real problem for women
  • 18. Iron Recommendations and Intakes (cont) 4. Food sources a. Meat (liver is best), poultry & fish  1/3 needs b. Milk, cheese (low absorption) & eggs  1/4 needs c. Enriched grains  1/4 needs d. Legumes, dark leafy vegetables, grains (nonheme iron) 1. low absorption due to other components (phytates in grains, oxalic acid in vegetables)
  • 19. Iron in Foods
  • 20. Iron Recommendations and Intakes (cont) 5. Contamination and Supplementation a. Contamination Iron 1. cookware a. Iron salts enter into food b. Cooking in an iron pot can increase the iron in the food as much as 500% b. Supplements 1. pregnant women 2. ferrous sulfate
  • 21. Iron Contamination
  • 22. III. Zinc (Zn) A. Roles in the Body 1. Important in many enzyme systems a. genetic materials b. digestive enzymes c. heme synthesis d. essential fatty acid metabolism e. CHO metabolism f. protein synthesis g. metabolism of alcohol h. free radical disposal i. release vitamin A stores
  • 23. Zinc (cont) B. Zn Absorption and Metabolism 1. metallothionein a. Zn binding protein b. regulates Zn absorption 2. Zn transport a. Albumin b. Transferrin 3. Zn interaction w/ copper & iron a. high zinc causes low copper absorption 1. Copper binds to metallothionein (trapped) b. binds w/ transferrin --> decreases iron absorption c. high Fe intakes cause low Zn absorption
  • 24. Zinc in the Body
  • 25. Zinc (cont) C. Zinc Deficiency 1. low intake 2. high phytate (grains and cereals or unleavened bread) 3. symptoms 1. growth retardation 2. arrested sexual maturation 3. decreased taste and digestive function 4. impaired immune response 5. central nervous system and brain affected
  • 26. Zinc deficiency (cont) Symptoms (cont) 6. slowed wound healing 7. affects vitamin A function 8. disturbs thyroid function and metabolic rate 4. Vulnerable groups 1. pregnant women 2. young children 3. elderly 4. poor
  • 27. Zinc (cont) D. Zinc Toxicity 1. Related to overuse of supplements 2. Small doses over time a. can affect the heart (interfere with copper) 3. Larger doses a. diarrhea, vomiting, fever, anemia, exhaustion 4. Zinc Recommendations and Intakes a. RDA men = 15 mg/day b. RDA women 12 mg/day
  • 28. Zinc (cont) E. Food sources 1. meats 2. shellfish 3. liver
  • 29. Zinc in Foods
  • 30. IV. Iodide A. Function 1. Part of thyroid hormones a. Thyroid hormones control BMR B. Deficiency 1. Goiter a. low Iodide intake (simple goiter) b. high goitrogen intake (toxic goiter) 1. thyroid antagonist 2. Goitrogens are found in cabbage, cauliflower, broccoli, brussel sprouts (few others)
  • 31. Goiter
  • 32. Iodine (cont) goiter (cont) c. causes sluggishness and weight gain 2. cretinism a. Iodine deficiency in utero b. Severe mental retardation C. Toxicity 1. 2000 µg/day toxic
  • 33. Iodine (cont) C. Iodine Recommendations and Intakes 1. RDA men and women 150 µg/day 2. U.S. intake 200-500 µg/day 3. 2000 µg/day toxic 4. Sources a. coastal areas --> seafood b. variable in soil c. iodized salt d. food processing
  • 34. V. Fluoride A. Roles in body 1. make bones and teeth resistant to decay B. Fluoridation and dental caries 1. decreased tooth decay where water fluoridated C. Fluoridation and Osteoporosis 1. unclear whether beneficial or detrimental
  • 35. Fluoride (cont) D. Fluoride Toxicity 1. moderate intakes a. mottled teeth 2. high intake (water) a. nausea b. diarrhea c. chest pain d. itching e. vomiting
  • 36. Population (%) Using Fluoridated Water
  • 37. VI. Chromium A. Roles in the Body 1. glucose tolerance factor a. potentiates insulin action b. increases glucose uptake by cells B. Chromium Recommendations 1. estimated safe and adequate intake a. 50-200 µg/day
  • 38. Chromium (cont) 2. sources a. liver b. brewer's yeast c. nuts d. cheeses e. whole grains(unrefined foods)
  • 39. Chromium (cont) C. Chromium Supplements 1. used to treat glucose abnormalities 2. chromium picolinate a. hypothesized 1. reduces body fat 2. increases lean body weight b. controlled experiments 1. no effect over placebo 2. one study increased fat gain.
  • 40. VII. Selenium A. Roles in the Body 1. antioxidant a. Enzyme glutathione reductase 1. Prevents free-radical formation 2. Functions with vitamin E 2. Thyroid gland a. Conversion of T4 to T3 (active hormone) B. Selenium intake 1. Soil concentration varies in the world 2. Intake dependent on soil
  • 41. Selenium (cont) C. Deficiency 1. Relationship between Se intake and heart disease 2. Relationship between Se intake and certain cancers (skin) D. Selenium toxicity 1. RDA is 70 ug/day for men, 55 for women 2. 1 mg/day is toxic a. vomiting, diarrhea, loss of hair and nails, skin lesions