Microminerals: Iron, Zinc, and Beyond

1. Microminerals/Trace Elements • Minerals that comprise < 0.01% of the body weight • Needed in concentrations of 1 PPM (part per million) or less; < 100 mg needed per day • RDAs have been established for 6 of these elements • Iron, zinc, copper, iodine, selenium, and molybdenum • Adequate intakes have been estimated for three • Manganese, fluoride, chromium • Many are involved as cofactors in enzymes

2. Iron • Ferric (3+) and ferrous (2+) forms the only oxidation states found in the body and in food. • Food forms are either heme or non-heme iron • Heme forms (derived from hemoglobin and myoglobin) are found mostly in animal products • Non-heme forms are principally found in plants and require more digestion prior to absorption; supplements are generally nonheme iron • Many foods are fortified with iorn including flour, corn meal, and rice. Table 12-2, p. 419

3. “Good” chelators: Acids (ascorbic, citric, tartaric); sugars; meat products; mucin “Inhibitors”: polyphenols such as those found in coffee and tea; oxalic acid; phytates; EDTA; calcium, zinc, manganese, nickel Fig. 12-2, p. 421

4. Storage = liver, bone marrow, spleen p. 422

5. Cellular iron influences the synthesis of apoferritin at the translation level. Release of iron from stores requires mobilization of Fe3+ and the use of reducing substances such as riboflavin, niacin, and/or vitamin C . Uptake by tissues depends on the transferrin saturation level and the presence of a tranferrin receptor (TfR2) on the cell Fig. 12-4, p. 426

6. Functions: • Energy Production • In heme proteins - hemoglobin, myoglobin, cytochromes, In iron-sulfur proteins - several in electron transport chain, aconitase and ferrochelatase • Other Enzymes • monooxygenases, dioxygenases, and oxidases, • aconitase (krebs cycle) • Peroxidases • oxidoreductases • Ribonucleotide reductase • Glycerolphosphate dehydrogenase Fig. 12-5, p. 428

7. Daily needs cannot be met by absorbed iron. Therefore, it is highly conserved and recycled. Losses are from GI tract, skin, kidney Fig. 12-6, p. 432

8. Deficiency: Iron Deficiency and Iron Deficiency Anemia Fig. 12-7, p. 433

9. Toxicity: Hemochromatosis or iron overload

10. Zinc • Found in all organs and tissues; highest in bone, liver, kidney, muscle and skin • Can exist in different valence states but in the body is always found in its divalent form (Zn2+) • Found in many sources, but zinc from plant sources is lower in content and not as easily absorbed as Zn associated with meat. Table 12-3, p. 436

11. Enhancers of absorption: citric acid, picolinic acid, histidine, cysteine, glutathione, low zinc status Inhibitors: phytate, oxalate, polyphenols, fibers, folic acid, divalent cations Fig. 12-8, p. 438

12. Fig. 12-10, p. 440

13. Carbonic anhydrase Alkaline phosphatase Alcohol dehydrogenase Superoxide dismutase Involved in at least 70 and probably as many as 200 different reactions. Is a part of more enzyme systems than all the other trace elements combined. Table 12-4, p. 441

14. Table 12-5, p. 446

15. Fig. 12-12, p. 447

16. Fig. 12-13, p. 450

17. p. 451a

18. p. 451b

19. p. 452a

20. p. 452b

21. p. 452c

22. Fig. 12-14, p. 456

23. Fig. 12-15, p. 457

24. Fig. 12-16, p. 458

25. p. 459a

26. p. 459b

27. p. 459c

28. p. 460a

29. p. 460b

30. Fig. 12-17, p. 464

31. Fig. 12-18, p. 464

32. Fig. 12-19, p. 465

33. Fig. 12-20, p. 468

34. Fig. 12-21, p. 469

35. p. 470

36. Fig. 12-22, p. 470

37. Fig. 12-23, p. 471

38. p. 472

39. Table 12-6, p. 473

40. p. 474

41. Fig. 12-24, p. 478

42. p. 478

43. Fig. 12-25, p. 479

44. Fig. 12-25a, p. 479

45. Fig. 12-25b, p. 479

46. Table 12-7, p. 481

47. Table 12-1a, p. 418

48. Table 12-1, p. 418

49. Table 12-1b, p. 418