Adequacy of Zinc Intakes in Relation to Requirement Estimates

Reference from the joint report of FAO/WHO expert consultation of Human Vitamins and Minerals verbatim.

32. AO/IAEA/WHO. 1996. Trace elements in Human nutrition and health. Geneva, World Health Organization.

43. Gibson, R.S. & Ferguson, E.L. 1998. Assessment of dietary zinc in a population. Am. J. Clin. Nutr., 68(suppl.): 430S-434S

The risk for inadequate zinc intakes in children has been evaluated by using the suggested estimates of zinc requirements (32) and by using data available on food composition and dietary intake in different parts of the world (43).

37. Fischer, P.W.F., Giroux, A. & L'Abbé, M.R. 1984. Effect of zinc supplementation on copper status in adult man. Am. J. Clin. Nutr., 40: 743-6.

38. Yadrick, M.K., Kenney, M.A. & Winterfeldt, E.A. 1989. Iron, copper, and zinc status: response to supplementation with zinc or zinc and iron in adult females. Am. J. Clin. Nutr., 49: 145-50.

39. Patterson, W.P., Winkelmann, M. & Perry, M.C. 1985. Zinc-induced copper deficiency: megamineral sideroblastic anemia. Ann. Internal Med.. 103: 385-6.

40. Porter, K.G., McMaster, D., Elmes, M.E. & Love, A.H.G. 1977. Anemia and low serum-copper during zinc therapy. Lancet, II: 774.

41. Hooper, P.L., Visconti, L., Garry, P.J. & Johnson, G.E. 1980. Zinc lowers high-density lipoprotein-cholesterol levels. JAMA, 244: 1960-2.

42. Chandra, R.K. 1984. Excessive intake of zinc impairs immune responses. JAMA, 252: 1443-6.

For this assessment it was assumed that the distribution of zinc requirements is Gaussian with a CV of 15 percent and that the correlation between intake and requirement is very low. Zinc absorption from diets in Malawi, Kenya, Mexico, and Guatemala was estimated to be 15 percent based on the high phytate-zinc molar ratio (37-42) in these diets, whereas an absorption of 30 percent was assumed for diets in Ghana, Guatemala, Egypt, and Papua New Guinea.

43. Gibson, R.S. & Ferguson, E.L. 1998. Assessment of dietary zinc in a population. Am. J. Clin. Nutr., 68(suppl.): 430S-434S

Fermented maize and cassava products (kenkey, banku, and gari) in Ghana, yeast leavened wheat-based bread in Egypt, and the use of sago with a low phytate content as the staple in the New Guinean diets were assumed to result in a lower phytate-zinc molar ratio and a better availability. With this approach 68–94 percent of the children were estimated to be at risk for zinc deficiency in these populations, with the exception of Egypt where the estimate was 36 percent (43).

44. Ruz, M., Castillo-Duran, C., Lara, X., Codoceo, J., Rebolledo, A. & Atalah, E. 1997. A 14-mo zinc-supplementation trial in apparently healthy Chilean preschool children. Am. J. Clin. Nutr., 66: 1406-13.

The average daily zinc intakes of these children were 3.7-6.9 mg (56-105 μmol). Most of the zinc supplementation studies have not provided dietary intake data, which could be used to identify the zinc intake critical for growth effects. In a recent study in Chile, positive effects on height gain in boys after 14 months of zinc supplementation was noted (44). The intake in the placebo group at the start was 6.3 ± 1.3 mg/day (96 ± 20 μmol/day) (n=49).

45. Krebs, N.F., Reidinger, C.J., Hartley, S., Robertson, A.D. & Hambidge, K.M. 1995. Zinc supplementation during lactation: effects on maternal status and milk zinc concentrations. Am. J. Clin. Nutr., 61: 1030-6.

Because only 15 percent of the zinc intake of the Chilean children was derived from flesh foods, availability was assumed to be relatively low. Krebs et al (45) observed no effect of zinc supplementation on human-milk zinc content or on maternal status of a group of lactating women and judged their intake sufficient to maintain adequate zinc status through 7 months or more of lactation. The mean zinc intake of the non-supplemented women was 13.0 ± 3.4 mg/day (199 ± 52 μmol/day).

32. AO/IAEA/WHO. 1996. Trace elements in Human nutrition and health. Geneva, World Health Organization.

10. Johnson, P.E., Hunt, C.D., Milne, D.B. & Mullen, L.K. 1993. Homeostatic control of zinc metabolism in men: zinc excretion and balance in men fed diets low in zinc. Am. J. Clin. Nutr., 57: 557-565.

44. Ruz, M., Castillo-Duran, C., Lara, X., Codoceo, J., Rebolledo, A. & Atalah, E. 1997. A 14-mo zinc-supplementation trial in apparently healthy Chilean preschool children. Am. J. Clin. Nutr., 66: 1406-13.

46. Ruz, M., Cavan, K.R., Bettger, W.J. & Gibson, R.S. 1992. Erythrocytes, erythrocyte membranes, neutrophils and platelets as biopsy materials for the assessment of zinc status in Humans. Br. J. Nutr., 68: 515-27.

47. Gibson, R.S. & Huddle, J.M. 1998. Suboptimal zinc status in pregnant Malawian women: its association with low intakes of poorly available zinc, frequent reproductive cycling, and malaria. Am. J. Clin. Nutr., 67: 702-9.

The efficient homeostatic mechanisms for maintaining body zinc content at low intakes, which formed the basis for the estimates of physiologic requirements in the FAO/IAEA/WHO 1996 report (32), as well as the presumed negative impact of a highphytate diet on zinc status, were confirmed in recent experimental studies (10, 44, 46, 47).

10. Johnson, P.E., Hunt, C.D., Milne, D.B. & Mullen, L.K. 1993. Homeostatic control of zinc metabolism in men: zinc excretion and balance in men fed diets low in zinc. Am. J. Clin. Nutr., 57: 557-565.

46. Ruz, M., Cavan, K.R., Bettger, W.J. & Gibson, R.S. 1992. Erythrocytes, erythrocyte membranes, neutrophils and platelets as biopsy materials for the assessment of zinc status in Humans. Br. J. Nutr., 68: 515-27.

Reductions in urinary and faecal losses maintained normal plasma zinc concentrations over 5 weeks in 11 men with intakes of 2.45 mg zinc/day (37 μmol/day) or higher in a diet with a presumably high availability (10). In a similar repletion-depletion study with 15 men, an intake of 4 mg/day (61 μmol/day) from a diet with a molar phytate-zinc ratio of 58 for 7 weeks resulted in a reduction of urinary zinc excretion from 0.52 ± 0.18 to 0.28 ± 0.15 mg/day (7.9 ± 2.8 μmol/day to 4.3 ± 2.3 μmol/day) (46).

14. Beck, F.W.J., Prasad, A.S. & Kaplan, J. 1997. Changes in cytokine production and T cell subpopulations in experimentally induced zinc-deficient Humans. Am. J. Physiol. 272: E1002-7.

17. Fairweather-Tait, S.J., Jackson, M.J., Fox, T.E., Wharf, S.G., Eagles, J. & Groghan, P.C. 1993. The measurement of exchangeable pools of zinc using the stable isotope 70Zn. Br. J. Nutr., 70: 221-34.

47. Gibson, R.S. & Huddle, J.M. 1998. Suboptimal zinc status in pregnant Malawian women: its association with low intakes of poorly available zinc, frequent reproductive cycling, and malaria. Am. J. Clin. Nutr., 67: 702-9.

A significant reduction of plasma zinc concentrations and changes in cellular immune response were observed. Effects on immunity were also observed when a zinc-restricted diet with a high phytate content (molar ratio approximately 20) was consumed by five young male volunteers for 20–24 weeks (14). Sub-optimal zinc status has also been documented in pregnant women consuming diets with high phytate-zinc ratios (>17) (47). Frequent reproductive cycling and high malaria prevalence seemed to contribute to the impairment of zinc status.

Conclusion

32. AO/IAEA/WHO. 1996. Trace elements in Human nutrition and health. Geneva, World Health Organization.

In conclusion, the approach used for derivation of average individual requirements of zinc used in the FAO/IAEA/WHO 1996 report (32) and the resulting estimates still seem valid and useful for assessment of the adequacy of zinc intakes in population groups and for planning diets for defined population groups.