Calcium metabolism phytate

We have not completed the analyses of self-chosen diets consumed by the subjects in HS-II and HS-III, but preliminary indications are that there was a wide range in intakes of calcium and of phytate/ calcium molar ratios. Stools and urine were collected while the self-chosen diets were being collected. Comparison of calcium metabolic balance parameters when consuming the self-chosen diets and the controlled diets of HS-II may provide an insight on dietary calcium requirement by these individuals. Some advocate the present RDA of 800 mg for adult men is too low (17), however, unpublished (R.D. Reynolds et al.) data from dietary intakes in a developing country indicate much lower usual intakes of calcium with relatively high phytate/calcium molar ratio. 

Might antagonize verapamil Might induce hypercalcemia with thiazide diuretics Fiber laxatives (variable), oxalates, phytates, and sulfates can decrease calcium absorption if given concomitantiy Phenytoin, barbiturates, carbamazepine, rifampin increase vitamin D metabolism... 

Two metabolic balance studies were conducted using healthy adult men to study the effect of phytate on bioavailability of dietary calcium. Dietary treatments were each 15 days in duration. In the first study, a mean daily calcium balance of 208+58 (SD) mg was observed when 2.0 g of phytate from 36 g of whole wheat bran was consumed daily with 1100 mg of calcium, phytate/calcium molar ratio 0.11. Calcium balance was 184+87 mg when 36 g of dephytinized bran was consumed with the same intake of calcium, phytate/calcium molar ratio 0.01. In the second study, calcium intake was 740 mg/day. 

Two metabolic balance studies conducted in our laboratory have yielded information relative to the effect of phytate and dietary fiber on calcium bioavailabilty. In the first study, a relatively high intake of dietary fiber was consumed with a 10-fold difference in phytate intake from wheat bran. In the second study three levels of phytate were consumed with a low amount of dephytinized bran as the principal dietary fiber source. The two higher phytate levels in the latter study were attained using sodium phytate. 

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