title: High dietary calcium intakes reduce zinc absorption and balance in humans.
abstract: 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.
authors.affiliation: Mineral Bioavailability Laboratory, Jean Mayer US Department of Agriculture, HNRCA, Tufts University, Boston, MA 02111, USA. wood_mb@hnrc.tufts.edu
authors.forename: R J
authors.initials: RJ
authors.lastname: Wood
authors.forename: J J
authors.initials: JJ
authors.lastname: Zheng
mesh_terms: D000042:Absorption / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001682:Biological Availability; D001835:Body Weight / Q000502:physiology; D002119:Calcium Carbonate / Q000494:pharmacology; D002136:Calcium, Dietary / Q000008:administration & dosage* / Q000494:pharmacology; D015930:Diet Records; D005243:Feces / Q000737:chemistry; D005260:Female; D005527:Food, Fortified; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009751:Nutritional Requirements; D017698:Postmenopause / Q000378:metabolism / Q000502:physiology; D011795:Surveys and Questionnaires; D015032:Zinc / Q000032:analysis / Q000378:metabolism* / Q000493:pharmacokinetics*
chemical_list: D002136:Calcium, Dietary; D006859:Hydrogen; D002119:Calcium Carbonate; D015032:Zinc