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Am J Clin Nutr. 2009 Mar;89(3):839-43. doi: 10.3945/ajcn.2008.27175. Epub 2009 Jan 28.

Dietary calcium does not exacerbate phytate inhibition of zinc absorption by women from conventional diets.

Author information

1
US Department of Agriculture-Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA. janetrhunt@gmail.com

Abstract

BACKGROUND:

Although calcium inhibits zinc bioavailability in rats, especially from high-phytate diets, the effect of calcium on zinc absorption by humans from practical diets remains unclear.

OBJECTIVE:

The objective was to test the inhibitory effect of dietary calcium, in Western diets with high and low phytate content, on zinc absorption.

DESIGN:

Using a 2 x 2 factorial design, zinc absorption was determined in 10 healthy women from 1-d diets with moderate and high calcium contents of approximately 700 and 1800 mg/d and low and high phytate contents of approximately 440 and 1800 mg/d. Absorption was measured by using extrinsically added (65)Zn and subsequent whole-body scintillation counting.

RESULTS:

Mean (+/-SE) fractional zinc absorption was 32.8 +/- 2.3% from the moderate-calcium, low-phytate diet; 26.9 +/- 2.4% from the moderate-calcium, high-phytate diet; 39.4 +/- 2.4% from the high-calcium, low-phytate diet; and 26.2 +/- 2.3% from the high-calcium, high-phytate diet. The respective values for absolute zinc absorption were 3.8 +/- 0.3, 3.0 +/- 0.3, 4.5 +/- 0.3, and 3.2 +/- 0.3 mg/d. Phytate significantly reduced fractional zinc absorption by approximately 10 percentage points and reduced absolute zinc absorption by 25%, or approximately 1 mg/d. Differences in dietary calcium did not affect zinc absorption, regardless of a high or low dietary phytate content.

CONCLUSIONS:

In healthy women consuming 1-d menus of ordinary foods (some fortified with calcium), dietary phytate reduces zinc absorption, but calcium does not impair zinc absorption, regardless of whether dietary phytate is low or high.

PMID:
19176739
DOI:
10.3945/ajcn.2008.27175
[Indexed for MEDLINE]
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