High dietary calcium intakes reduce zinc absorption and balance in humans
RJ Wood and JJ Zheng
Mineral Bioavailability Laboratory, Jean Mayer US Department of Agriculture, HNRCA, Tufts University, Boston, MA 02111, USA.
Optimal calcium intakes of 37.5 mmol(1500 mg)/d have been proposed for elderly people. We investigated the effects of calcium supplementation on zinc absorption and balance in 18 relatively healthy, postmenopausal women aged 59-86 y. All subjects received a standardized basal diet of typical foods supplying 269 mumol (17.6 mg) Zn/d and 22.2 mmol (890 mg) Ca/d during the 36-d study. In two of three experimental periods, an additional 11.7 mmol (468 mg) Ca/d as either milk or an inorganic calcium phosphate supplement was provided. Net zinc absorption and zinc balance were significantly reduced by approximately 2 mg/d during both high-calcium treatments. In a second study, conducted in a separate group of men and women aged 21-69 y, a whole-gut lavage, zinc- absorption test was used to investigate the acute effect of a 15-mmol CaCO3 (600 mg Ca) supplement, with and without extra zinc, on zinc absorption from a single test meal supplying 111.7 mumol (7.3 mg) Zn. Zinc absorption was reduced significantly by 50% when the calcium supplement was given with the meal. Inclusion of an extra 119.3 mumol (7.8 mg) Zn as part of a calcium supplement offset the detrimental effect of calcium on zinc absorption. Our findings suggest that high- calcium diets can reduce net zinc absorption and balance and may increase the zinc requirement in adult humans.
American Journal of Clinical Nutrition, Vol 65, 1803-1809, Copyright © 1997 by The American Society for Clinical Nutrition, Inc
Calcium Research Results
Calcium, magnesium, zinc, fluoride, and phosphorous work together to form and maintain bones and teeth (Somer, 1995; Mahan et al, 1996).
The ratio of calcium to phosphorous and calcium to magnesium are important in the absorption, use, and excretion of these minerals (Somer, 1995; Mahan et al, 1996).
Optimal calcium absorption depends on adequate amounts of vitamin D to be available (Somer, 1995; Mahan et al, 1996).
Calcium competes with magnesium, copper, zinc and manganese for intestinal absorption (Somer, 1995).
Calcium requirements go up in the presence of excess dietary protein, fat, or phosphorous (Somer, 1995).
Calcium citrate increases absorption of aluminum from foods whereas other types of calcium reduce aluminum and lead absorption. (Somer, 1995).
Calcium may help control blood pressure by working against the negative effects of sodium chloride (Somer, 1995; Mahan et al, 1996).
The ratio of calcium to magnesium plays a role in heart disease development (Somer, 1995).