 When women hit menopause and they're overly shut down, the estrogen level in their body drops 95%. This is good news for the endometrium, the aligning of the uterus. Otherwise, the constant estrogen signaling could eventually result in endometrial cancer. In fact, maybe that's why menopause evolved to protect the uterus from cancer. Lower estrogen levels are also good for lowering breast cancer risk. In postmenopausal women, relatively high blood levels of estrogen are associated with more than double the increased risk for breast cancer. Estrogen levels drop 95% at menopause, but not to zero because other tissues can make estrogen like our own fat cells. This probably explains the increase in breast cancer risk in obese postmenopausal women. More fatty tissue means more estrogen production. And we learned that soy phytoestrogens can block the production of estrogen, such that drinking a glass of soy milk with each meal can cut estrogen levels in half in premenopausal women. But levels in postmenopausal women are already down 95%, and because of that, many women suffer from hot flashes. Might lowering levels even further with soy make menopausal symptoms even worse? Estrogen treatment is very effective in reducing menopausal symptoms. Unfortunately, the downside is not only the uterine cancer, but blood clots, strokes, and cognitive impairment. Taking progesterone-type compounds with the estrogen helps prevent the uterine cancer, but increases the risk of heart attacks, more stroke risk, breast cancer, more clots, and dementia. So what's a woman to do? Well, the 80% hot flashes figure is not universal. Maybe 80 to 85% in European and American women, but it may be as low as just 15% in places like Japan. In fact, there's not even a word for it in the Japanese language, which supports how relatively rare it is. Maybe the phytoestrogens in soy are helping? The association between soy product intake and the occurrence of hot flashes was examined by following 1,000 Japanese women before they started menopause over time to see who developed hot flashes and who didn't. And those women who were eating like 4 ounces of tofu a day appeared to cut their risk in half compared to women who only ate like an ounce or two a day, suggesting soy products are protected. But maybe soy intake is just a marker for a healthier diet overall? A study in China found that consumption of whole-plant foods in general seemed to be associated with decreased menopausal symptoms. So to see if soy was something special, you'd have to put it to the test. Studies like this of soy phytoestrogens in pill form showed extraordinary results, a significant drop in hot flash presence, number, and severity. From 100% of women suffering at the beginning to only 31% suffering by the end of three months, the average number of hot flashes dropped from about 120 a month down to 12. But the problem with studies like these is that there's no control group to control for the placebo effect. If you look at all the hormone trials, even the women who got the placebo sugar pills had up to a 60% reduction in hot flashes over the years. That's why any therapy purported to reduce such symptoms must be assessed in blinded trials against the placebo because of the large placebo effect, and also because menopausal symptoms often decline on their own over time. So if you saw a study like this, where they gave women a soy protein powder and saw a nice drop in hot flashes over the next 12 weeks, you'd think, ah, it looks pretty effective. But that's the placebo powder group. Here's the group that got the soy. Significantly better than placebo, but it's important to recognize how powerful the placebo effect can be. Over the past 20 years, more than 50 clinical trials have evaluated the effects of soy foods and supplements on the alleviation of hot flashes. Compiling the best ones together, the placebo groups got about a 20% drop in hot flash severity. The soy groups achieved about a 45% drop. So on average, the soy did about 25% better than control. There have been two studies that compared soy phytoestrogens head-to-head against hormones, and in one study they actually seemed pretty comparable in terms of reducing hot flashes, muscle and joint pain, and vaginal dryness compared to placebo, though in the other, soy did better than placebo, but estrogen and progesterone therapy did better than them both. But the soy has the benefit of not increasing cancer heart disease and stroke risk.