Soy Does Not Impact Calcium Metabolism

WEST LAFAYETTE, Ind.--Soy protein and isoflavones do not appear to impact calcium metabolism, though they have been shown to have beneficial effects on bone health, according to researchers from Purdue University. In their study, published in the American Journal of Clinical Nutrition (81, 4:916-22, 2005), 15 postmenopausal women followed three one-month dietary interventions in a crossover design: soy protein isolate with isoflavones, soy protein isolate without isoflavones and a casein-whey protein isolate. Urinary calcium excretion was significantly less on the soy diets; however total fecal calcium excretion, bone deposition and resorption, and calcium retention were not affected by any of the diets. The researchers concluded the lower urinary calcium was not associated with improved calcium retention, indicating isoflavones did not significantly affect calcium metabolism.