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Soy Guide for Women

July 9, 2010 Written by JP    [Font too small?]

I’m not sure how I feel about the concept of meaningful coincidences or synchronicity. But that doesn’t stop me from assigning significance to patterns that seem to crop up for whatever reason. In the past few weeks several people that I know have expressed a concern about the estrogenic properties of soy foods and supplements. I’ve covered this issue in previous columns, but thought this might be a good time to report on the most recent evidence available on this controversial topic.

Dr. Mark Messina, of the Loma Linda University Department of Nutrition, is one the of the preeminent soy researchers in the world. He has a piece in the July 2010 edition of the Journal of Nutrition which provides a historical perspective on the scientific study of soy and soy isoflavones (phytoestrogens). Dr. Messina references research dating back to the 1940’s that revealed that soy isoflavones were capable of causing fertility problems in sheep. Mark goes on to document data from the 1950’s that illustrates a paradoxical anti-estrogenic activity of soy phytoestrogens. The concluding remarks of his review state that, “in vitro and animal research has raised questions about the safety of isoflavone exposure for certain subsets of the population, although the human data are largely inconsistent with these concerns”. (1)

By the time a scientific review is published there is usually new research available that could be added to it. I’ve identified several studies which became available after the submission of Dr. Messina’s summary article. The bulk of the data focuses on the effects of soy isoflavones and cancer risk in female populations. A recent Korean epidemiological study examined the diets of 358 women with breast cancer (BC) in comparison to 360 age-matched women who were cancer free. The intake of dietary soy was considered in the context of a larger 103-item food frequency questionnaire. On average, the female participants consumed about 3 oz. of soy per day – yielding approximately 15 mg of isoflavones daily. The women eating the largest amount of soy foods were 64% less likely to have breast cancer. A more specific analysis revealed that postmenopausal women with high soy intake were protected to an even greater extent – a 92% lower incidence of BC. (2)

Population-based studies are useful, however they’re not considered the “gold standard” of research because they only provide observational evidence. The August 2010 issue of the journal Climacteric provides a more highly regarded, intervention trial known as an “open-label study”. A total of 395 postmenopausal women were given 70 mg/day of a standardized soy isoflavone extract over a 3 year period. Endometrial biopsies, mammographies and transvaginal ultrasonographies were performed at the beginning and end of the trial. These tests aimed to answer the question: Does soy cause hormone sensitive tissue to grow and, thereby, contribute to cancer risk? The findings revealed the following data:

  • No cases of tissue overgrowth (hyperplasia) or cancer were detected based in the biopsy results.
  • No significant changes in endometrial thickness or in mammography results were noted at the 3 year mark.
  • 99% of the patients and physicians rated the “global safety” of the soy extract as “excellent” or “good”.

There were several instances of side-effects. In all, 8 of the 395 women reported breast pain or tenderness and menstrual bleeding irregularities. However, on the whole, the authors of the trial concluded that, “daily administration of 70 mg of a specific, standardized isoflavone extract for 3 years could be a safe treatment for endometrium and breast”. (3)

Soy Intake May Reduce Breast Cancer Risk – Click Image to Enlarge
Source: JAMA. 2009;302(22):2437-2443. (link)

Two other relevant studies were published in the past few months regarding soy and women’s health. The first reported that larger intake of isoflavones were inversely associated with the risk of benign breast lumps known as fibroadenomas. Two of the most prominent phytoestrogens in soy, daidzein and genistein, conferred a 64% and 61% reduction in risk respectively. The second trial investigated the efficacy of 100 mg/day of soy isoflavones in a group of 50 women with menopausal hot flashes and mood disturbances. After 3 months, hot flash occurrence and severity declined by 69%. Depressed mood was similarly reduced by approximately 64%. The researchers were also hoping to find positive effects in the participants’ blood pressure readings and body mass index. However, no significant changes in diastolic or systolic blood pressure or weight were demonstrated. (4,5)

I’ve always adopted a rather cautious approach to soy. Even with all of the positive studies I’ve come across, I still harbor some degree of concern about the precise effects of the plant-based estrogens contain therein. But my hope is that further trials will help to calm my suspicions. There’s one upcoming study in particular that I think will be very revealing. The SPARE (Soy Phytoestrogens As Replacement Estrogen) trial is currently being conducted at the University of Miami School of Medicine and will involve 283 women. Various health markers including estrogen levels, hip and spine bone density, menopausal symptoms, serum lipids and thyroid function will be assessed over a 2 year period. A higher dosage of 200 mg/day of soy isoflavones will be provided to half of the women, aged 45 to 60, with the remaining volunteers receiving a placebo. When the SPARE study results become available, I will most certainly report on them. In the meantime, I think it’s prudent to interpret the previously mentioned research with cautious optimism. (6)

Be well!


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Posted in Food and Drink, Women's Health

10 Comments & Updates to “Soy Guide for Women”

  1. Jo Says:

    I personally have avoided soy since a friend of mine with metastatic cancer was told to avoid it by her oncologist. In retrospect, I have personally seen oncologists “cover all their bases”–and not that I blame them, given what they’re up against and with no real cure to offer but only hopes of remission–so it probably isn’t wise for me to take what a physician told a dying woman as the last word for myself. Lately I have been reconsidering soy and am doing so even more after reading this post.

    However, my mind falls to the recent observation by researchers at the Harvard School of Public Health that increased heart disease risk seems to be associated solely with processed meats and not unprocessed ones. Many soy products, such as tofu, are among the most processed things on the shelves. Are these studies attempting to probe the effects of the phytoestrogens in soy taking the how processed the soy consumed was? YES, there is a huge and unfounded leap to assume that processing has anything to do with phytoestrogens effects, but my curiosity strikes me.

    And my question for you is: would you be concerned if your daughter/wife/sister to eats soy regularly?

  2. JP Says:


    Excellent questions. I’ll answer the easiest one first. 🙂

    At this point, I wouldn’t encourage anyone to make soy a cornerstone of their diet. But I also wouldn’t discourage anyone who tolerates soy from eating it from time to time. Especially if the soy in question is organic. If it’s fermented, all the better.

    I’m sure processing does have some impact on the health effects of soy. My understanding about the processed meat issue is that “processed” generally = “cured” with nitrates and nitrites. This is not an issue with soy. Having said that, there are certainly other concerns associated with highly processed foods – high sodium content, etc. But in some instances, there can be positive attributes of processing as well. The fermentation process is one example.


    The vast majority of studies on soy haven’t tried to categorize which soy foods are responsible for the health benefits and risks. If anything, soy isoflavone and protein content are the focal points. However these are found in most soy foods regardless of processing.

    A cursory review of the medical literature doesn’t seem to support a negative association between certain processed soy products, such as miso and tofu, and increased health risks.



    Be well!


  3. Brittney Kara Says:

    I have been a vegetarian for my whole life and have grown up eating tofu and soy products. I have recently just had live blood cell analysis done and my cells were healthy and strong. I happen to believe in the power of soy, if it is organic as JB stated, to be a viable source of protein for the body. The problem that I have right now with the soy industry is how the soy isolates are being processed and some companies are actually mixing a toxic ingredient know as hexane in the processing of the soy bean. It is very important to look to see if the soy product is certified organic and if the company is committed to using non-hexane products. It just comes down to being an informed consumer and knowing what you are putting in your body.

    Thanks JP for the insight and for being a warrior out there in this toxic food industry

    Brittney Kara

  4. JP Says:

    Thank you, Brittney.

    When I first read the name of your site … I was a little concerned! 🙂

    I agree 100% that we need to be informed and proactive consumers. Sharing what we learn, as you do, inspires others to do the same and spreads the wealth of knowledge. Keep up the good work!

    Be well!


  5. Brittney Kara Says:

    Thanks JP! Yeah.. its a a bit of a joke. I am a super positive person, but I am angry about what the corporations have done to our food industry and I want people to get mad about it so we can make a positive social change.

    It is all about being the change you want to see in the world!

    Brittney Kara

  6. JP Says:


    An excellent attitude! Count me in! 🙂

    Be well!


  7. Iggy Dalrymple Says:

    Since I was diagnosed with prostate cancer I’ve been adding 1 level tsp of genistein to my morning coffee. My PSA has dropped more than 1/2, but I take other supplements as well. I won’t really know if my condition has improved until my next biopsy. The genistein and other supplements have not affected my libido.

    I also eat oats and barley but try to avoid wheat and red meat.

  8. JP Says:


    Do you know approximately how much genistein a teaspoon provides?

    Great news about your PSA drop. That’s a good indicator of reduced inflammation in the prostate.

    It’s encouraging to note the lack of effect on your libido. The same cannot be said for some men using the more conventional approach.

    Be well!


  9. Iggy Dalrymple Says:

    I use Source Naturals non-GMO Genistein Powder. The label suggests 1 tsp/twice per day in water or juice. 1 teaspoon = 2 1/2 grams yielding:
    genistein ————- 10 mg
    daidzein ———- 42 1/2 mg
    glycitein ————- 25 mg
    total isoflavones – 77 1/2 mg
    I hope the active ingredients dissolve because I usually
    just drink the coffee and don’t bother with eating the “mud”.

  10. JP Says:

    Thank you, Iggy.

    I wouldn’t bet on the genistein/water solubility issue. You may want to drink the sludge.




    Be well!


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