Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health

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Zinc And Iron Nutriture: Neuropsychological Function Of Women

Harold H. Sandstead, M.D., Division of Human Nutrition, Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, TX 77555-1109

This work is being done in collaboration with Nancy W. Alcock, Ph.D.; Hari H. Dayal, Ph.D.; Norman G. Egger, M.D.; and V. M. S. Ramanujam, Ph.D., from our department, and James G. Penland, Ph.D., of the USDA-ARS Human Nutrition Research Center in Grand Forks, N.D., and Katsuhiko Yokoi, M.D., Ph.D., of the Department of Social Medicine, University of Kyoto Medical School, Kyoto, Japan.

Our work is in progress. We are testing the hypothesis: zinc and iron repletion will improve neuromotor and cognitive functions of young women. Our study is based on the common occurrence of mild iron and zinc deficiencies among young women and the essentiality of iron and zinc for cognition.

Due to a decrease in consumption of red meat, the average intake of iron and zinc of young U.S. women decreased 40 percent from 1977 to 1985 (Briggs and Schweigert, 1990). This change in food choice accounts for the median iron (9.8 mg) and zinc (7.4 mg) intakes found by NHANES II (Murphy and Calloway, 1986), which were 69 and 59 percent of the calculated need at 20 percent bioavailability (Halberg and Rossander-Hultén, 1991; King and Turnland, 1989). Reflecting low iron intakes, the 25th percentile for serum ferritin was 14 µg/L, a level at which bone marrow iron is absent (Halberg and Rossander-Hultén, 1991).

It was found through regression analysis of food frequency data that red meat was one of five predictors of serum ferritin concentration in young women (N = 38, R² = 0.53, p = 0.0001) and one of four predictors of zinc status, as indicated by the plasma zinc disappearance constant (k) (N = 19, R² = 0.63, p = 0.005) (Yokoi et al., 1994).

In our study, zinc status and serum ferritin concentrations were related (Yokoi et al., 1994). Serum ferritin was lower when plasma zinc was less than 70 µg/dL (p < 0.03) in 18 subjects in whom the disappearance of injected ⁶⁷Zn from plasma was measured, and plasma zinc disappearance and plasma zinc turnover were increased when serum ferritin was less than 20 µg/L (p < 0.05 and 0.01). When plasma zinc concentration was < 70 µg/dL, the disappearance of injected ⁶⁷Zn was increased (p < 0.05). Regression analysis found that serum ferritin concentrations and the 30- to 60-min disappearance of injected ⁶⁷Zn were inversely and nonlinearly related (N = 18, R² = 0.777, p < 0.0003). The nonlinearity was probably caused by an increased intestinal absorption of zinc as iron status decreased (Pollack et al., 1965).

The essentiality of iron for human neuropsychological function was suggested 75 years ago (in retrospect) by findings in children with hookworm (International Health Board, 1919; Waite and Nelson, 1919). More recently, iron status was related to cognition of children (Oski and Honig, 1978; Pollitt et al., 1982; Webb and Oski, 1973), and to EEG power and lateralization, and cognition of young adults (Tucker et al., 1984).

The essentiality of zinc for human cognition was shown by experimental deficiency (Henkin et al., 1975; Penland et al., 1997) and repletion (Penland, 1997; Sandstead, 1992) studies. A recent double-blind randomized depletion-repletion study of 11 men found abnormal neuromotor, attention, perception, short-term visual memory, and spatial functions (p <0.05)

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