Soy Milk Isoflavones Show Superior Bioavailability

NORWICH, England--Soy milk provides more bioavailable isoflavones than other soy foods, according to a study conducted by scientists from the Universities of East Anglia and Surrey, in England, in conjunction with the Cincinnati Children's Hospital Medical Center.

Researchers administered three different soy foods--soy milk, textured vegetable protein and tempeh--in a single bolus dose (0.44 mg/kg body weight) to 21 premenopausal and 17 postmenopausal women, and 21 men, in a randomized, crossover design. Serum isoflavone concentrations increased rapidly in all test subjects after the ingestion of each soy food, and genistein concentrations exceeded daidzein concentrations in serum. Consumption of tempeh produced higher serum peak levels of both daidzein and genistein compared with textured vegetable protein. However, soy milk was absorbed faster and peak levels of isoflavones were attained earlier, in comparison to the other soy foods.

The study appeared in the Journal of Nutrition (136, 1:45-51, 2006).