Does soy food consumption explain why Japanese women appearto beso protected from hot flash symptoms?
When women hit menopause and their ovaries shut down, the estrogen level in their bodydrops95percent. This is good news for the endometrium, the lining of the uterus. Otherwise, the constant estrogen signaling could eventually result in endometrial cancer. In fact, thatmay bewhy menopause evolved: to protect the uterus from cancer. Lower estrogen levelsare also beneficial forloweringbreast cancer risk. In postmenopausal women, relatively high blood levels of estrogen are associated with a more than double increased risk for breast cancer.But why do estrogen levels drop 95percentat menopause, but notall the way downto zero? Because estrogencan be made by other tissues, like our own fat cells, and“this probably explains the increase in[breast cancer]risk inobesepostmenopausal women.”More fatty tissue means more estrogen production.
In my earlier videoHow to Block Breast Cancer’s Estrogen-Producing Enzymes, I discussedhowsoy phytoestrogens can block the production of estrogen, such that drinking a glass of soy milk with each meal cancutestrogen levels inhalfin premenopausal women. Butestrogenlevels inpostmenopausal women are already down 95percent, and,because of that, many women, approximately 8 in 10,sufferfrom hot flashes. Might lowering levels even further with soy make menopausal symptoms even worse?That’s the subject of my videoSoy Phytoestrogens for Menopause Hot Flashes.
Estrogen treatmentreducesmenopausal symptomsvery effectively, but,unfortunately,itsdownsides includenot only the uterine cancer, but blood clots, strokes, and cognitive impairment, as well. Taking progesterone-type compoundswiththe estrogen prevents uterine cancer, but increases the risk of heart attacks,morestroke, breast cancer,moreclots, and dementia.What’s a woman to do?
The 80percenthot flashes figureisnot universal.Eightyto 85percentofEuropean and American womenmayexperiencehot flashes, butasfewas 15percentof women may be affectedin places like Japan. In fact, thereisn’teven atermfor it in the Japanese language, whichsupportshow relatively rare it is.Couldthe phytoestrogens in soybehelping?
Researchersexaminedthe“association between soy product intake and the occurrence of hot flashes”by following a thousand Japanese womenover time, frombefore they started menopause, to see who developed hot flashes and who didn’t. As you can see at 2:34 inmyvideo,those womeneatingaroundfourounces of tofu a day appeared to cut their risk in half,compared to women onlyeatingan ounce or two a day, suggesting soy products are protective. But,could it be thatsoy intake is just a marker for a healthier diet over all?
A study in Chinafoundthat consumption of“whole plant foods”in general seemed to be associated with decreased menopausal symptoms,soin orderto see if soyhad aspecialrole, you’d have to put it to the test.
As you can see at 3:10 inmyvideo,soy phytoestrogens in pill formshowedextraordinary results,includinga significantdecreasein hot flash“presence,number [frequency]and severity.”At the start of the study,100percentof women sufferedhot flashes, and that droppedto only 31percentby the end ofthreemonths. The average number of hot flashesalso dropped,from about 120 a month down toonly12in 90 days.Exciting findings, but the problemwiththis study andsomeothers like itis that therewas no control group to control for the placebo effect. If youlookat all the hormone trials, even the women who got the placebo sugar pills had up toarounda 60percentreduction in hot flashes over the years. That’s why any“therapiespurported to reduce such symptoms must be assessed in blinded trials against a placeboor a validated therapybecause of the large placebo effect…and also because…menopausesymptoms often decline”on their own over time.
To illustrate this point, see thefindings of astudy I show at 4:00 inmyvideo.Researchersgavewomen a soy protein powder and saw a nice drop in hot flashes over the next 12 weeks. Those results on their ownmake the soy supplementationlook pretty effective, butthose were results fromtheplacebopowder group.Thestudysubjects whoactuallygot the soyachievedresultssignificantlybetterthan placebo,which demonstrates howimportantit isto recognize how powerful the placebo effect can be. Over the past 20 years, more than 50 clinical trials haveevaluatedthe effects of soy foods and supplements on the alleviation of hot flashes. Compiling the best ones together, the placebo groups got about a 20percentdrop in hot flash severity,whilethe soy groups achieved about a 45percentdrop. So, on average, the soy did about 25percentbetter than control, as you can see at 4:31 inmyvideo.
There have been two studies that compared soy phytoestrogens head–to–head against hormones.In one study, they actuallyseemedpretty comparable, in terms of reducing hot flashes, muscle and joint pain, and vagin*l dryness, compared to placebo,as you can see at 4:50 inmyvideo.In the otherstudy, however, soy did better than placebo, but estrogen and progesterone therapydidbetter than both.But,soy has“the benefit of noincreased risk of breast and uterinecanceror cardiovascular disease,” such asheart disease and stroke.
KEY TAKEAWAYS
- After menopause, a woman’s estrogen level drops by 95 percent, which benefits her endometrium, the uterine lining, and lowers breast cancer risk.
- Soy phytoestrogens can block estrogen production, such that drinking a glass of soy milk at each meal can halve estrogen levels in premenopausal women.
- Although estrogen treatments may effectively reduce symptoms of menopause, they have myriad downsides, including uterine cancer, blood clots, strokes, and cognitive impairment, and taking it with progesterone-type compounds may also increase heart attack, stroke, breast cancer, clot, and dementia risks.
- Hot flashes are suffered by approximately 80 percent of postmenopausal European and American women, but only about 15 percent of women in Japan, for example.
- Researchers found that those eating around four ounces of tofu a day appeared to halve their risk of hot flashes, compared to those who only ate one or two daily ounces, suggesting soy products are protective.
- More than 50 clinical trials have studied the effects of soy foods and supplements on hot flashes, and the best studies found about a 25 percent improvement by soy over placebo controls in the severity of hot flashes.
- Of the two studies comparing soy phytoestrogens against hormones, one determined soy to be fairly comparable with regards to reducing hot flashes, muscle and joint pain, as well as vagin*l dryness, compared to placebo, while the other found that soy did better than placebo but the estrogen and progesterone therapy exceeded both in effectiveness.
- Soy, however, provides the benefit without the increased risks of cancers of the breast and uterus or heart disease, stroke, and other cardiovascular disease.
Why does soy help some women, but not others?SeemyvideoHow to ConvertIntoan Equol Producer.
I discuss more about the risks of hormone replacement therapy inHow Did Doctors Not Know About the Risks of Hormone Therapy?.
What aboutPlant-Based Bioidentical Hormones? Check out the videoand find out.
For more on soy, see:
- Is Soy Healthy for Breast Cancer Survivors?
- GMO Soy and Breast Cancer
- Flashback Friday: Who Shouldn’t EatSoy?
In health,
Michael Greger, M.D.
PS: If you haven’t yet, you can subscribe to my free videoshereand watch my live presentations:
- 2019:Evidence-Based Weight Loss
- 2016:How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers
- 2015:Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet
- 2014:From Table to Able: Combating Disabling Diseases with Food
- 2013:More Than an Apple a Day
- 2012:Uprooting the Leading Causes of Death
