Soyfoods are known for being uniquely rich dietary sources of isoflavones, often referred to as phytoestrogens. Now, a two year clinical trial involving approximately 300 postmenopausal Canadian women found that daily supplementation with soy isoflavones is safe and can lead to a number of benefits. For example, isoflavones significantly decreased LDL-cholesterol by about 6 percent. Taking isoflavones also improved leg strength as measured by one particular type of squatting exercise. In addition, exercise and isoflavones individually maintained bone mineral density at the hip when compared to a placebo. Unexpectedly, however, this benefit was lost when exercise was combined with isoflavones. A previous study found the combination was actually quite beneficial.
Isoflavones also reduced adverse reports of menopausal symptoms by more than half compared to non-isoflavone groups. Menopausal symptoms that were classified as adverse events included breast tenderness, decreased concentration, depression, fatigue, hot flashes, insomnia, numbness, vaginal dryness, vaginal itching, night sweats, subjective weight gain, migraine headaches, anxiety, irritability, and changes in bleeding patterns. Finally, isoflavone supplementation was shown to be safe. Safety was assessed by looking at the effects on endometrial thickness and mammographic density. Endometrial thickness and mammographic density assess risk of endometrial and breast cancer, respectively.
The results of this large, two year trial, suggest that consuming soyfoods, the richest source of isoflavones, may benefit the health of postmenopausal women in several different ways.
Chilibeck PD, Vatanparast H, Pierson R, et al. Effect of exercise training combined with isoflavone supplementation on bone and lipids in postmenopausal women: A randomized clinical trial. J Bone Miner Res, 2012.