Soy contains active compounds known as isoflavones. Some of these isoflavones, like genistein, have estrogen-like effects. Because the conventional estrogen replacement therapy used to treat menopause symptoms has been shown to increase the risk of stroke, most notably in the Women’s Health Initiative study that was halted in 2004, Chinese researchers wanted to see if soy isoflavones could be a viable alternative. Their study was published in the January 2012 issue of Menopause.

The researchers divided 90 postmenopausal women age 45 to 60 into one of three treatment groups:

1. Daily placebo (fake pill)

2. Daily dose of 84 mg of soy germ isoflavones

3. Daily dose of 126 mg of soy germ isoflavones

All of the participants experienced a reduction in hot flashes; however, the most significant effects were noticed in the two soy isoflavone groups. There was no significant change in circulating estrogens in the women taking the isoflavones, so the researchers conclude that it’s unlikely the improvement was due to the influence of female hormones.

Cancer connection

Because soy isoflavones can influence hormones, specifically estrogen, there has been some question about whether women at high risk of estrogen-dependent breast cancers (those with a family history or a previous diagnosis) should take soy isoflavones.

“Prior to 2009, we did not have any human data on soy isoflavone intake and breast cancer recurrence rates, so the universal recommendation was to avoid soy consumption,” explains naturopathic oncologist and Wellness Times Editorial Advisor Tina Kaczor, ND. “That has changed dramatically in the last three years. None of the human studies have shown an increase in risk of recurrence in premenopausal or post-menopausal women.”

Kaczor explains that in two studies there was a significantly lower risk of breast cancer recurrence in post-menopausal women who were estrogen-receptor positive and had the highest soy food consumption, indicating that soy foods may actually be protective against these cancers.

“Given that the human data is so consistent, I am confident that soy foods are not going to raise the risk of breast cancer recurrence,” she says.