High dietary calcium intakes reduce zinc absorption and balance in humans

Am J Clin Nutr. 1997 Jun;65(6):1803-9. doi: 10.1093/ajcn/65.6.1803.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Absorption / physiology
  • Adult
  • Aged
  • Aged, 80 and over
  • Analysis of Variance
  • Biological Availability
  • Body Weight / physiology
  • Calcium Carbonate / pharmacology
  • Calcium, Dietary / administration & dosage*
  • Calcium, Dietary / pharmacology
  • Diet Records
  • Feces / chemistry
  • Female
  • Food, Fortified
  • Humans
  • Hydrogen / metabolism
  • Male
  • Middle Aged
  • Nutritional Requirements
  • Postmenopause / metabolism
  • Postmenopause / physiology
  • Surveys and Questionnaires
  • Zinc / analysis
  • Zinc / metabolism*
  • Zinc / pharmacokinetics*


  • Calcium, Dietary
  • Hydrogen
  • Calcium Carbonate
  • Zinc