New data from Japan suggest a second major role for chromium, Mertz says--the stimulation of DNA transcription within cells. While it's still too early to be sure, he says, chromium seems to be a part of a very specific protein that influences a cell's nucleic acid metabolism.
Work by Herta Spencer is showing that through their dietary choices, many people risk developing serious zinc deficiencies. New data by Spencer, chief of the metabolic section at the Veterans Administration Hospital in Hines, Ill., on obese men hospitalized to lose weight, show that weight loss generally correlates with losing zinc. Zinc deficiency can cause skin rashes, appetite loss, poor wound healing, mental lethargy, hair loss and taste disturbances.
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The recommended daily allowance (RDA) for zinc is 15 mg. However, many diets -- even those where weight reduction is not a goal -- are deficient in this essential metal. One analysis Spencer performed on hospital diets showed that zinc levels in supposedly well-balanced, calorie-adequate diets could range from 4.6 mg to 19 mg per day. Zinc levels tended to vary with dietary levels of animal protein, especially fish and red meat (though legumes, wheat germ and cheese are also good sources). Because weight-reducing diets are frequently low in animal protein, they risk being low in zinc, Spencer says. However, it's not just the inherent zinc level that makes such diets a threat to zinc sufficiency. Preliminary data suggest that protein is needed to carry zinc across the intestinal lining so that it can be absorbed, she says. What's more, certain chemicals like EDTA -- used for removing lead from the body -- will pull huge quantities of zinc, her research shows. In persons who had been excreting 0.4 mg of zinc daily in urine, three days of EDTA treatment was enough to pull 64 mg of zinc from their body stores.
Ironically, the use of concentrated zinc supplements to counteract this problem may only create another--a calcium deficiency. In a just-completed study, Spencer found that high levels (140 mg) of zinc reduced the body's ability to absorb calcium -- from a normal 69 percent to only 39 percent -- when the diet contained only a quarter of the RDA for calcium. Spencer notes that for women whose diets are already seriously low in calcium -- as most U.S. women's diets are -- such zinc supplementation might increase their risk of postmenopausal bone loss.