Soy Doesn't Affect BMD

FARMINGTON, Conn.—According to researchers at the University of Connecticut Health Center, because soy protein and isoflavones (either alone or together) did not affect bone mineral density (BMD), they should not be considered as effective interventions for preserving skeletal health in older women. The negative correlation between dietary protein and bone turnover suggests increasing protein intakes may suppress skeletal turnover (Am J Clin Nutr. 2009;90:234-42). Researchers conducted a randomized, double blind, placebo-controlled clinical trial in 131 healthy ambulatory women older than 60 years. A total of 97 women completed the trial. After a one-month baseline period, subjects were randomly assigned into one of four intervention groups: soy protein (18 g) + isoflavone tablets (105 mg isoflavone aglycone equivalents), soy protein + placebo tablets, control protein + isoflavone tablets, and control protein + placebo tablets.
Consumption of protein powder and isoflavone pills did not differ between groups, and compliance with the study powder and pills was 80 to 90 percent. No significant differences in BMD were observed between groups from baseline to one year after the intervention or in BMD change between equol and non-equol producers. However, there were significant negative correlations between total dietary protein (per kg) and markers of bone turnover (P<0.05).