This double-blind, 15-month pilot study was designed to investigate the effect of soy
protein isolate with varying concentrations of isoflavones
on early postmenopausal bone loss and lipids.
A total of 65 women, with a mean age of 55 years and 7.5 years since menopause, were randomized to one of three groups; soy
protein with 96 mg isoflavones
with 52 mg isoflavones
/day, or soy
(< 4 mg isoflavones
was given for 9 months and then discontinued; participants were followed for an additional 6 months. Bone mineral density
(BMD) and blood lipids were measured during this time.
Measurement of serum isoflavones
at 3 months showed dose-related increases in the three groups. There was no significant effect of the soy
supplements on BMD of the spine or femoral neck in any of the three groups. BMD increased significantly in the trochanter at 9 months (P
= 0.0219) and at 15 months (P
< 0.05) in the group given isoflavone-free soy
compared with the other two groups. There was no significant effect of soy
on lipid metabolism at the end of the intervention.
The present study did not find a significant positive effect of soy
protein isolate supplemented with isoflavones
on BMD and the serum lipid profile in early postmenopausal women