Soy! Everything you wanted to know. Or should.

Posted by on Sep 20, 2010 in hot flash, HRT | 6 comments

Confusion about soy abounds. Does it help hot flashes, improve bone health or prevent heart disease by lowering cholesterol? Or it is no more effective than placebo?  Does its effectiveness rely upon the ratio of certain isoflavones — the plant-based estrogen-like components, which in soy include  genistein (50-55% of total isoflavone content of soy), daidzein (40% to 45% of total isoflavone content) and glyceitein (5% to 10% of total isoflavone content) — or is the metabolite S-equol the only component that will yield estrogen-like benefits without negative health risks?

Are you perplexed? I sure am, which is why this particular post may be a bit to scientific for a few and too long for others. however, it’s important to understand some of the reasons why soy continues to intrigue, baffle and well, show differing results in terms of benefits for menopausal symptoms. So I encourage you to bear with me.

I’ve written previously that there are several key reasons why researchers have yet to make any any definitive conclusions about soy during menopause, such as poorly designed studies, small number of study participants, wide range of ages and years from menopause, and the fact that the pros and cons of an agent or strategy are not being studied for a long enough period of time. In other cases, there is an inconsistency in the soy preparation being studied and the ratio of isoflavones may differ; alternatively, researchers have not accounted for the presence of other isoflavones in the diet, which may influence results.

Does a new study that appears in the advanced online edition of Maturitas journal, comparing low-dose hormone therapy to soy powder in women with hot flashes, offer any anything more definitive or different than what’s gone before?


The 16-week study enrolled 60 women between the ages of 40 and 60, all of whom had had their last period at least 12 months, had the same frequency of hot flashes (more than 8 per 24 hours), had not used any hormonal treatment in the 6 months leading up to the study period, and were not currently using any drugs that lower blood fats, treat diabetes, taking other soy-based products or using herbal supplements.

Women participating in the study were randomly assigned:

  1. low-dose hormone therapy (a Activelle ®tablet daily, better known as Activella® in the US) plus a placebo powder or
  2. 2 portions daily of dietary soy supplementation powder (comprising 45 mg isoflavone per dose) plus a placebo tablet, or
  3. 1 placebo tablet/2 portions placebo powder.

All women were first screened  for  current hormone levels, reproductive history, age at menopause, time since menopause, medication use and cigarette/alcohol consumption. During the study, they were asked to use a standardized scale to evaluate menopausal symptoms (hot flashes, heart discomfort, sleep, and muscle and joint problems) mood (depression, irritability, anxiety, physical/mental exhaustion) and sexual problems, bladder problems and vaginal dryness.

The results?

Both hormone therapy and soy supplementation were associated with significant improvements in hot flashes and joint/muscle pain (which declined by about 45.6% in the hormone group and 49.8% in the soy group) and in vaginal dryness (which decline d by 38.6% in the hormone group and 31.2% in the soy group) compared to women who took placebo. Improvements in mood scores were consistent between the three groups, indicating that other factors, such as caring and attention by medical practitioners throughout the study, may have played some role in wellbeing. Moreover, both treatments were considered safe with few side effects.

These results are quite promising, as they indicate that soy may indeed, offer an alternative to hormone therapy in menopausal women seeking relief. However, it’s important to consider the following:

  • Like many of its predecessors, the study is a small one.
  • The study length was short, lasting only 16 weeks, which some critics might say is too short a time period to elicit a satisfactory clinical response.
  • The researchers did not analyze whether or not the women actually took the drugs or soy consistently, and relied on their self-reports.

On the other hand:

  • The study followed strict Western scientific guidelines and the women and the researchers did not know who was taking what.
  • Symptoms were measured using a common quality of life scale whose goal it is to diminish errors by healthcare practitioners when analyzing results of questionnaires. This particular scale, better known as the MRS, is widely used and allows researchers to evaluate symptoms and treatment over time.

There has been a lot of criticism geared towards alternative treatments, such as acupuncture, herbs and Chinese medicine, as being shams, especially because there is no evidence supporting their use for addressing troublesome menopausal symptoms. Others will claim that the placebo effect is at play, i.e. a situation in which symptoms are relieved by an otherwise ineffective treatment due to expectations or beliefs. However, the researchers of this particular study point to the placebo effect in studies comparing estrogen to placebo, demonstrating for example, a 75% reduction in hot flashes among hormone users compared to a 57% reduction in hot flashes among women taking placebo.

The most important conclusion to be drawn is that there is early evidence that soy supplementation may be as effective as low-dose hormonal therapy in relieving certain vasomotor symptoms and possibly, vaginal dryness. We need more studies like this one, enrolling larger numbers of women, in order to definitively demonstrate benefit. Dollar for dollar, the monthly difference between the two treatments may only be about $30.  Yet, this is one of the first studies I’ve seen that followed enough rules to quiet the rioters. And that alone, is worth the price of admission.

Stay tuned. The fat lady hasn’t sung her soy aria as of yet.

[Special thanks to Reuters Health Executive Editor Ivan Oransky, for your continued support of my mission to provide timely, evidence-based information on menopause and midlife to my readers.]


  1. 9-20-2010

    I’m not a doctor or a scientist – but I did take soy for a point in time as an experiment with my doctor. It did what we had hoped it seemed to lessen hot flashes. It could have been a placebo (she tells me it might and my mind says it will). I was drinking 8oz a day for about a year. However, I had to discontinue use because amongst the issues I had was a fibroid. In some online searches of women communities about hysterectomies I found a post (with back-up comment) that her fibroid had shrunk after removing soy from her diet. I went off soy immediately (again, as an experiment) and my fibroid (and it’s side effects) shrunk. I did not end up having to have a hysterectomy. Again, this is one woman’s tale (with a couple of unknown to me women who also had the same experience). I guess what I would say is know as much as you can and be flexible in the outcome.

    • 9-20-2010

      Beth, you raise an interesting and important point – the relationship to soy to fibroids. I’ve seen reports of early exposure (infant) to soy formulations and later development of fibroids. And have heard anecdotal stories like yours’. In this particular study, which again, was short, the researchers did not observe any effects on the endometrium, or the lining of the uterus. It could be dose-related or time-related and like any “drug,” can have specific effects. It’s all individual. You did the right thing – you consulted with your practitioner, which is the first rule of thumb always. As you say – ‘know as much as you can and be flexible in the outcome.’

  2. 9-21-2010

    Soy is very harmful to pre-menopausal women. I have endometriosis and it is especially harmful to women who have PCOS, endometriosis, or hormone problems not related to estrogen deficiency. I ate and drank tons of soy products 4 years ago, thinking it was healthy, but it made my cycles and my sister’s cycles irregular, then I was rushed to the emergency room with a endometrioma cyst that burst open, bleeding. The endometrioma was a size of an orange and caused horrible pain.
    I have seen multiple medical specialists and 3 registered dieticians/nutritionists. They all say to never eat soy thanks to its phytoestrogen- especially infants, children, men, and pre-menopausal women.
    Soy farming is subsidized by the government, just like corn (to produce corn syrup and feed). Soy has lobbyists protecting it and those who tout soy are tied to the industry.
    Soy is a recent additive to our diet, which ideally should be the hunter-gatherer diet we are genetically programmed for. Then civilization came along. It takes hundreds of thousands of years for our digestion system to evolve to eat something. We, as a species, are not meant to eat any “new” processed foods, including anything with soy.
    The problem is soy plus toxins in our environment puts our hormones on a crazy, hyper-drive chaos. Too much phytoestrogen plus estrogen-stimulating toxins in cosmetics, pesticides, plastic products can stimulate a 3-year old girl to develop pubic hair and breasts (source: the book “Endometriosis” by Mary Lou Ballweig, pp. 330.)Unless a doctor says to eat soybeans, soybean oil (which is in everything, grrr), tofu, soy milk, etc., I would never touch it again.

    • 9-21-2010

      I appreciate your comments but I do feel that they are blown a bit out of proportion. Asian populations have been eating soy products for centuries with no harmful effects. It’s dangerous always to take an either/or all or nothing stance without backing up the claims with data.

      I am sorry for your health troubles. I always recommend that readers check with a licensed health professional prior to using any strategy to address their menopausal symptoms. Clearly, soy is not a good option for you nor is it a good option for women who have difficulty with fibroids.

      Good health to you.

  3. 9-27-2010

    Thanks for reporting on good research. It is clear to me that soy is helpful for relief of menopausal complaints. To give soy a bad rap when we alternately rely on prescriptive hormones and drugs that are associated with so many risks is (to me) absurd. The science communities bias against natural products seems to cause them to hold natural products to a higher standard than drugs. I guess its easier to do research on single drugs since there are fewer variables to account for. (bookmarked this article)

    • 9-27-2010

      Thank you Dr. Mittag. I appreciate the comment and you stopping by. I am not sure if natural products are held to higher or different standards. However, I would like to see their incorporation into our therapeutic system and more broad acceptance by the Allopathic medical community.


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