Calcium does not inhibit zinc absorption
05-09-2009 11:26 AM
Calcium does not inhibit zinc absorption
According to this current research:
Am J Clin Nutr. 2009 Mar;89(3):839-43.
Dietary calcium does not exacerbate phytate inhibition of zinc absorption by women from conventional diets.
Hunt JR, Beiseigel JM.
US Department of Agriculture-Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA.
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.
FYI, phytate, aka phytic acid, is primarily found in uncooked, unsprouted whole grains, seeds, and legumes. Phytate is destroyed by enzymes when bread is leavened by yeast, as well as by heat in the baking or cooking process. So a high phytate diet would include a lot of raw grains, beans, and seeds.
Thoughts or comments?
05-10-2009 09:19 AM
I don't think this necessarily applies to the AM reader. The fear of calcium interfering with zinc absorption deals with the dosing of calcium and zinc at the same time i.e drinking bed time protein shake, taking supps with calcium alongside ZMA.
This study applies to a diet high in calcium interfering with zinc absorption without offering any information on the time of dosing.
However, someone correct me if I'm wrong.
05-10-2009 09:39 AM
plus i thought calcium had more of a negative influence on magnesium than zinc-this being reason for not taking zma close to taking calcium.
Originally Posted by miked512
05-10-2009 10:07 AM
If anything, the study just proves once again that the rat animal model isn't the best emulator of human physiology. I love reading posts or supplement writeups by people who quote rat studies. Granted, when we have nothing better to go off of, the rat model must suffice. But its just funny to see how every day, we realize more and more that our physiology isn't entirely predicted by animal models.
Thanks for the study!
05-12-2009 03:27 PM
Yes, I'm not sure anyone thought calcium interfered with zinc absorption. It interferes with magnesium absorption. Though, I don't really know if it does affect zinc, but apparently this study would refute that anyways.
Originally Posted by thebigt
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