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

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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 [almost equal to]700 and 1800 mg/d and low and high phytate contents of [almost equal to]440 and 1800 mg/d. Absorption was measured by using extrinsically added ⁶⁵Zn 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 [almost equal to]10 percentage points and reduced absolute zinc absorption by 25%, or [almost equal to]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.
Hunt, Janet R. , Beiseigel, Jeannemarie M.
Includes references
American journal of clinical nutrition AJN 2009 Mar., v. 89, no. 3
American Society for Clinical Nutrition
Journal Articles, USDA Authors, Peer-Reviewed
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