What about soy?

I’d like to talk about soy today because I get a lot of questions about it. There is a lot of information and disinformation available out there and it’s hard to cut through the chaff to get to the wheat, so to speak. But I think I’ve gotten a decent handle on the information and the sources of disinformation and that I can offer a decent recommendation. As I often do, I’ll offer the abbreviated version first, then a longer look into the arguments and data.

Short Version

Let’s start by reminding everyone that soy beans are a legume, similar to beans and lentils. The health benefits of legumes are legion. The web, and particularly the blogosphere, is rampant with articles both for and against soy. Almost all of the anti-soy arguments are derived from a single source, the Weston A. Price Foundation (WAPF), who advocate full fat, raw dairy, heavy meat consumption and advise you to pay no attention to your cholesterol. The WAPF bases their arguments around 4 basic tenets:

  1. The phytoestrogens in soy (i.e. isoflavones)
  2. The goiterogenic (anti-thyroid) properties of soy
  3. The presence of phytic acid in the husk of the soybeans
  4. The presence of trypsin inhibitors in soybeans

I’m guessing that almost everyone has heard of the first one and not about the other three. The quick summation of the data is:

  1. Phytoestrogens (plant based estrogen-like (NOT estrogen) substances) can be beneficial for breast cancer, menopause symptoms and prostate cancer. There is no evidence that they cause early menarche, alter normal breast development, cause gynecomastia in men, or have any effect on male fertility. Note for non-plant based readers: cows milk has very high levels of actual estrogens, not estrogen like substances. Forgoing soy products because of phytoestrogen concerns and then drinking cows milk is truly ridiculous. “The present data on men and children indicate that estrogens in (cow) milk were absorbed, and gonadotropin secretion was suppressed, followed by a decrease in testosterone secretion. Sexual maturation of prepubertal children could be affected by the ordinary intake of cow milk.”
  2. There is some evidence that soy can effect thyroid function of some animals, but there is no evidence that it causes thyroid problems in humans.
  3. Phytic acid can bind to some metals (iron, magnesium, etc.) and may block absorption in the intestine. This is the basis for the WAPF argument. Newer research (most since 2000 and ongoing) shows a number of exciting effects of phytic acid in human health including: a powerful anti-cancer agent and a powerful anti-inflammatory. Further, phytic acid is present in all grains and legumes, not just soy.
  4. I can find no data to suggest that the small amount of trypsin inhibition in soy is of any concern to human health.
  5. Soy has a significant effect in lowering cholesterol, clearly helps protect against heart disease, moderates blood sugars in Type II diabetes, helps protect the kidneys, and is a complete protein for humans. It’s not a panacea for an otherwise bad diet, but is an excellent adjunct to a nutritious diet.
  6. Final thought: the less processed the soy (like all foods) the more nutritious it is. Tofu, tempeh, miso, tamari, soy milk, soy nuts and edamame are all good ways to eat soy. Foods with “soy protein isolates” should be avoided; think of them as the equivalent of high fructose corn sugar as compared to whole corn.
Long Version

With that out of the way, a little background. I have talked to a lot of people who avoid soy like the plague. They’ve read too much bad press about soy and have come to believe it is really bad for you. Trying to understand this fear, I turned to the internet and Googled “is soy bad for you?” and got an amazing number of hits. But as I worked my way through these sites (Authoritynutrition.com, paleoleap.com, and foodrenegade.com to name a few) I found an amazing similarity to the information being provided. Literally, it was always organized in the same way and the same claims, with more or (usually) less documentation and source references. And, if you went and read the references, they were usually quite old and based on rodent studies and all of them, ultimately, led to the Weston A Price Foundation (WAPF). I was completely unfamiliar with WAPF, so I, of course, started digging. I invite to you read the Wikipedia page here. From the Wiki page I noted a dissenting article by John Robbins, the host and founder of the Food Revolution Summit that I reported on back in May. So I bought John Robbin’s book “No Happy Cows: Dispatches from the Frontlines of the Food Revolution” and read the chapter where he walks the reader through the WAPF arguments and presents a cogent, well researched and well written rebuttal. Finally, I turned to Dr. Michael Greger of Nutritionfacts.org for his take on isoflavones and found, almost by accident, some data about phytic acid. This led me back to the PubMed database and a quick search confirmed Dr. Greger’s assertions. Enjoy!

First, let me say that I’m not going to spend a lot of time talking about the benefits of soy. I outlined them in point #5 above and I’ll say only that there is ample data out there for anyone who is interested to confirm. I’d suggest the PubMed database or Dr. Greger’s NutritionFacts.org.

  1. Isoflavones (phytoestrogens). Everyone needs to understand, from the beginning, that soy does not contain any estrogen. It does have some compounds called isoflavones that act a bit like estrogen in the body. To get a better understanding of what this means, think of a lock, some keys, and a locked door. Many cells have estrogen receptors, which are like locks. Just like when you have a lot of keys on a key ring and you don’t know which one opens the locked door, some of the keys will actually fit in the lock, but will not open the door. This is what an isoflavone does. It binds to the estrogen receptor on a cell, but does not activate the cell the way estrogen does. Estrogen is the key that opens the lock on the door. It fits in the receptor and then triggers a number of responses in the cell. Isoflavones, no matter how well they fit the lock, won’t trigger the same responses that estrogen does. Understanding this explains a great deal of the confusion that surrounds isoflavones. I can’t stress this enough – isoflavones ARE NOT estrogens. WAPF has the following statement on their Soy Alert site: “Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women“. So, let’s look at what we really know about soy isoflavones.
    1. breast cancer: isoflavones do not cause breast cancer nor do they increase the risk of breast cancer. In fact, that’s exactly backward. This review of the literature, published in April 2016 concludes:
      “Clinical trials consistently show that isoflavone intake
      does not adversely affect markers of breast cancer risk,
      including mammographic density and cell proliferation.
      Furthermore, prospective epidemiologic studies involv-
      ing over 11,000 women from the USA and China show
      that postdiagnosis soy intake statistically significantly re-
      duces recurrence and improves survival.”
    2. menopause: isoflavones not only don’t make menopausal symptoms worse, they are now considered “first line” treatment according to this June 2016 article in Gynecological Endocrinology.
    3. menarche (age of first menstruation): again, there is no evidence to suggest that soy intake induces an early menarche. As an aside, early menarche is associated with increased breast cancer risk, so given what we learned above, we would not logically associate soy with early menarche. Interestingly, the two nutritional factors that have been linked to early menarche are red meat consumption in this 2016 Journal of Nutrition article and cow milk consumption in this 2012 American Journal of Human Biology article.
    4. gynecomastia (breast development in men): a common theme I, personally, have heard. “Don’t eat soy or you’ll get man boobs”. But, as noted above, isoflavones are not estrogens and there is no evidence whatsoever that soy has any feminizing effects on human males. This 2010 article from Fertility and Sterility pretty much shut the door on that argument.
    5. Sperm counts: this got a lot of press a while back, when the Massachusetts General Hospital published this article in 2008. The study shows a statistically significant decrease in sperm concentration in men who reported higher soy intake. They did not find any statically significant differences in total sperm counts, sperm motility or sperm morphology. So, you have to ask, how can the total sperm counts be not statically significant, but sperm concentration can? Well, as you might guess, there was a trend, but not a statistically significant one, toward higher ejaculate volume in men who ate more soy. More to the point, even if you just look at the only significant finding of sperm concentration, the lowest levels were 76 (millions/mL), well above the low normal level of 30.
  2. Anti-thyroid effects of soy: Again, WAPF states: “Soy phytoestrogens are potent antithyroid agents that cause hypothyroidism and may cause thyroid cancer. In infants, consumption of soy formula has been linked to autoimmune thyroid disease”. But, for all of the hype, there is decidedly little written. It appears that this has a lot more traction in the lay literature than the medical/biomedical literature. I did find this 2007 article from the journal Thyroid that pretty much dispels this concern. I think it’s important to point out that soy based infant formulas were first introduced in 1929 and have been in widespread use for the last 85 years. There is no evidence to suggest that soy based formula is linked to autoimmune thyroid disease or any thyroid disease at all.
  3. Phytic acid: This was probably the most interesting/humorous part of the research. WAPF states: “High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets have caused growth problems in children.” It’s hard to know where to even begin with that statement, so I’ll just refer you to this 2016 Journal of Food Science article entitled “Phytic Acid: From Antinutritional to Multiple Protection Factor of Organic Systems”. To sum the article up, there is no evidence if any significant “antinutritional” effects of phytic acid and there are now so many well documented anti-cancer and anti-inflammatory benefits it’s hard to find justification for WAPF’s continued stance against phytic acid. Michael Greger, MD, in his book “How Not to Die” sums up phytates (phytic acid): “Phytates do have side effects, but they all appear to be good. High phytate intake has been associated with less heart disease, less diabetes, and fewer kidney stones. In fact, some researchers have suggested that phytates be considered an essential nutrient.”
  4. Trypsin inhibitors: WAPF states: “Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders. In test animals soy containing trypsin inhibitors caused stunted growth“. As I said in the short version, I have nothing to say here. My search of the PubMed site yielded no evidence of any issues with human health or digestion related to the small amount of trypsin inhibitors in soy. In fact, soy is known as one of the only “complete proteins” in the plant kingdom, providing all of the amino acids necessary for nutrition.

Final words: soy is a legume and has all of the health benefits of the legume family. Soy can and should be incorporated into a nutritious diet in one of the unprocessed forms I listed above.

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