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The Truth About Soy

April 21, 2009 Written by JP    [Font too small?]

Soy is one of the most controversial foods in both the conventional and natural health communities. Because current research on soy is still not conclusive, many conventional doctors take the position that moderation is the best policy. The holistic community is generally split on this topic. Some alternative practitioners claim that soy is a virtual super-food. Others warn of serious side effects associated with its use. My goal today is to provide a balanced update on the newest findings regarding soy consumption and women’s health.

Soy and Cancer

The Good, the Bad and the Ugly

One of the primary concerns about soy estrogens (isoflavones) is uncertainty as to how they may or may not behave like regular hormones. Based on the research, we know that soy phytoestrogens are not as powerful as prescribed hormone replacement. But, there’s also data that soy can help somewhat with many of the same symptoms as doctor prescribed hormones.

This leads to the question of safety. Does soy present the same adverse effects that are typically associated with conventional hormone replacement? A brand new study in the Journal of Nutrition addresses that concern. In it, 400 postmenopausal women were given either a placebo, 80 mg or 120 mg of soy isoflavones (plant estrogens) per day for a period of 2 years. The goal of the trial was to determine whether soy supplementation would increase breast density – an indicator of negative hormonal changes related to breast cancer.

The scientists performed digital mammograms at the beginning and end of the trial to determine the respective changes in the breast tissue density of each group. No difference was found among the placebo, 80mg or 120 mg soy groups. This led the authors of the study to conclude that, “isoflavone supplements did not modify breast density in postmenopausal women. These findings offer reassurance that isoflavones do not act like hormone replacement medication on breast density.”

Another positive trial is presented in the May 2008 issue of the International Journal of Food Sciences and Nutrition. That study tested the effects of soy protein on various markers relating to heart health. Here’s how the experiment was set up:

  • 52 postmenopausal women with high cholesterol were asked to consume a soy protein drink containing 50 grams of soy protein or an identical placebo that contained no soy phytoestrogens.
  • The trial lasted 10 weeks and blood tests were conducted to measure cholesterol and triglyceride levels at the beginning and end of the study.
  • The researchers also measured something called “PON1 activity”. PON1 makes up part of the “good” HDL cholesterol and is thought to help prevent heart disease.

The results of the investigation revealed that the women’s “bad” (LDL) cholesterol and triglycerides decreased significantly in the soy group. But there was a desirable increase in the protective factor PON1. These changes indicate that soy appears to reduce the risk of heart disease and strokes in post.

What we have so far are two studies that suggest that consuming soy is both health promoting and safe. But not every study on soy yields such promising results. The scientific literature contains two other recent trials that did not find any significant benefits. Here’s a brief description of both of those studies:

  • In April 2009, a 2 year investigation failed to find any anti-inflammatory effect in a group of 90 premenopausal women. The researchers were hoping to find a reduction in inflammation, which appears to support defenses against cancer and heart disease – two of leading causes of death in women of this age group.
  • Another study from March 2009 attempted to determine whether a daily dose of 120 mg soy isoflavones could help improve menopause related depression. 84 women were followed for a total of 16 weeks. They took standardized tests to establish their levels of depressive symptoms at weeks 0, 8 and 16 of the trial. The researchers did not find any statistical difference between the soy and placebo treatments. It is, however, important to note that no “relevant adverse events” were noted in either group as well.
Soy and Phytic Acid

Image Note: “Stored” = Fermented

As you can see, the findings are a mixed bag. I know that this isn’t necessarily reassuring when you’re trying to decide whether to use any given food or supplement. So here are some general guidelines that may help in making a decision about soy.

  1. Personally, I would only eat soy if I had a health-related reason to do so. I don’t think there’s any reason to go out of your way to use it if you’re generally healthy.
  2. If there is a good reason for you to use soy, be mindful of any negative effects on your digestive system, your hormonal activity and your thyroid function.
  3. Try to choose organic, non-genetically modified, fermented soy products, which may be better tolerated than generic soy foods. The fermentation process also diminishes the phytic acid content of soy beans. Phytic acid can inhibit the absorption of vital nutrients.

The debate about soy will likely be a long one. There’s a lot of research currently underway that will help to further clarify what kind of a role soy should play in the medical and nutritional realms. I’m perfectly willing to alter my position as new evidence becomes available. Until then, I personally choose to approach the use of soy from a cautious and scientifically founded position.

Be well!


Posted in Nutrition

9 Comments & Updates to “The Truth About Soy”

  1. lowcarber Says:

    Hmmm very interesting.. here in Japan Soy products are the norm. Every grocery store has at least 7 kinds of tofu, soy sprouts, and 30 kinds of miso. (fermented soy beans used in making miso soup)

    Soy products in Japan have been around forever and older people especially eat soy products everyday. Younger people are turning more to a western diet and stray from the traditional diet. In the traditional diet, miso soup is consumed at every meal and miso is often used to flavor meat or vegetables.

    As for the general health of people here in Japan..well lets just say that there are more centurions here than any other place in the world.. over 36,000 of them and increasing..
    Ask them what they eat every day.. tofu, miso fish and vegetables with a splash of meat here and there.

    But in the end it depends on the entire diet I think and genetics. See.. Japanese intestines are longer than westerners by 3 meters. Why? because of there diet is largely based on vegetables rather than meat. As Japanese eat more meat they are starting to find an increase in cancer of the intestines due largely to there diet it is believed. Eventually, evolution will help them out and adjust there intestines to match there diet. (for the younger generations) So I strongly beleive that diet should be driven by moderation and body type. I would be really interested in a study that compared the effects on Asians where soy is prevalent in there diet to westerners that are just starting to add it into there diet.

    Geez I just rambled.. any just a thought about soy..

  2. Iggy Dalrymple Says:

    I add about 1/2 tsp of genesteine to my cocoa but I forget why.

  3. JP Says:

    Interesting comments, LowCarber. Thanks!

    There are quite a few theories about why so many centenarians reside in Japan. Soy is one of the proposed reasons. That’s why I think it’s so important to evaluate soy in a scientific manner. By doing so, we might be able to determine if it is indeed an anti-aging super food.

    Thanks again for sharing your first-hand perspective. It’s nice to have a contact in one of the “Blue Zones” (the areas where people live the longest).

    Be well!


  4. JP Says:


    Maybe as part of an anti-cancer cocktail? A lot of men use it to support prostate health as well.

    I hope it wasn’t for memory support! 😉

    Be well!


  5. Jen Boda Says:

    Another great post. I think, in addition to the concerns about hormones, it is important to look at the fact that soy can be very heavy and many people are intolerant to it. Also, environmentally, it is one of the most monocropped, GMO foods out there, so there is a responsibility there as well.


  6. JP Says:

    I agree. Digestive issues are certainly something to consider. If someone decides to use soy, I do believe that GMO-free, organic and preferably fermented forms would likely be best.

    Be well!


  7. Earl H. Kinmonth Says:

    You state

    See.. Japanese intestines are longer than westerners by 3 meters. Why? because of there diet is largely based on vegetables rather than meat.

    Can you provide references to clinical studies that support this claim?

    If “vegetables” lead to longer intestines, than orthodox Hindus presumably have intestines than Japanese because they are complete vegetarians while that has never been the case for Japan.

    Incidentally, as a long term resident of Japan (nearly two decades), I would say that the (traditional) Japanese diet was grain, not vegetable based. And, contemporary Japanese eat a tremendous amount of junk food of both local and foreign origin.


  8. JP Says:


    I didn’t make the original comment but I wanted to reply because I’m not sure if the original poster will see your question. Below, I’ll post a link that offers some limited information about this topic.


    Be well!


  9. pi Says:

    Well, isn’t this interesting…

    More than 230,000 Japanese centenarians ‘missing’

    KYOTO, Japan — More than 234,000 people listed on government records as age 100 or older are actually missing and probably dead, in some cases long dead, the Justice Ministry said Friday.


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