Soya supplements do not protect against postmenopausal changesBMJ 2004; 329 doi: https://doi.org/10.1136/bmj.329.7457.68-a (Published 08 July 2004) Cite this as: BMJ 2004;329:68
Soya supplements containing naturally occurring oestrogen do not improve cognitive function, bone mineral density, or plasma lipids in healthy postmenopausal women, a new study says (JAMA 2004;292: 65-74).
The sudden decline in oestrogen levels after menopause coincides with the acceleration of several ageing processes, but because of the side effects of hormone replacement therapy some women have turned to naturally occurring oestrogens known as phytoestrogens (including isoflavones and lignans) that occur in plant foods such as soya beans, peas, fruit, vegetables, nuts, and grains.
In the study, Dr Yvonne van der Schouw of the Julius Center for Health Sciences and Primary Care at the University Medical Center, Utrecht, the Netherlands, and colleagues randomly assigned 202 healthy postmenopausal women aged 60 to 75 years to receive daily for 12 months either 25.6 g of soya protein (containing 99 mg of isoflavones) or a placebo. They were recruited from a population based sample in the Netherlands between April 2000 and September 2001.
The main outcomes were improved cognitive function, increased bone mineral density of the hip and lumbar spine (assessed with dual energy x ray absorptiometry scanning), and improved lipid levels (assessed by determining levels of Lp(a) lipoprotein, total cholesterol, low density lipoprotein, high density lipoprotein, and triglycerides).
Cognitive function, bone mineral density, and plasma lipids did not differ significantly between the groups after a year.
Forty nine participants (24%) did not complete the trial for various reasons, the most important being complaints relating to bloating and cramps in the gastrointestinal tract in the soya group and aversion to the taste of the soya supplement. Median duration of participation for those who dropped out was 79 days and there was no difference in the dropout rate between the two groups (24 dropped out from the placebo group, 25 from the soya group).
At one year, the bone mineral density in the placebo group had decreased by a mean of 0.009 g/cm2 in the intertrochanter region of the hip, whereas in the soya group it had increased by a mean of 0.004 g/cm2 (a difference in change in bone mineral density of 1.31% (95% confidence interval 0.002 to 0.025; P=0.02). Bone mineral density in the hip was 0.5% better in the soya group (−0.004 to 0.013; P=0.28) but in the spine, the soya group showed a drop in bone mineral density of 0.1% (−0.010 to 0.008; P=0.79).
In the soya group, the levels of low density lipoprotein and total cholesterol also remained constant, whereas in the placebo group they decreased slightly, but the differences again were not significant.