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The Absolute, Bottom Line,
Last Word Truth About Soy

Perhaps the single most common legume-based item in the vegetarian/vegan world is soy, which loosely refers to both the traditional Asian forms and the dozens of protein-rich meat and dairy substitutes that have become increasingly prevalent in the mainstream market through the years. Besides the various kinds of tofu, tempeh, and tamari, there are soy-based substitutes for virtually any kind of animal product you can think of, from soy chicken, ribs and bologna to soy milk, cheese and ice cream. The taste, texture and overall experience of these foods is, for the most part, uncanny…especially if you’ve made a full transition away from animal products. For this reason, soy products are often viewed as a godsend to many followers of a plant-based diet. After all, with products like these, it hardly feels like you’re sacrificing anything at all with your veggie regimen.

The good news in all of this is obvious: the transition to the plant-based diet is made infinitely easier because folks can basically substitute the meat and dairy products they’ve been used to eating with various soy “imposter” versions and barely taste the difference. This is why so many companies have joined the soy bandwagon and tapped into an ever-expanding new market of folks who do want to eat healthier, but, of course, do not want to alter their eating habits very much. To this end, soy has its place.

The bad news, however, is this: in the consumer’s zeal to replace all of their favorite animal products with soy substitutes over multiple servings per day, they neglect to realize that they are taking in large quantities of highly processed foods that are typically riddled with sodium and often loaded with fat. (And believe me, with the sheer number of easy-to-prepare or ready-to-eat soy products out there, this is easy to do.) Are they still better off doing this than eating animal products? Sure. But eating high quantities of soy products has its pitfalls, even though many of the anti-soy claims out there are either highly exaggerated or completely without merit altogether. And if it’s a non-organic soy product, then the downside of mega-soy overdosing is exacerbated.

Cause for concern? Read on…

Soyanoia: Putting Soy Paranoia in Perspective

Let’s once-and-for-all address a few of the more pervasive concerns, myths and blatant untruths about soy, based on some of the latest “research.” First of all, much of this anti-soy research is referring to animal-based studies, which are notoriously inaccurate and unreliable in their relevance to humans. One well-known study in particular was done with rats (who, like all animals, have a completely different physiology than us humans), where they were fed an insanely high amount of soy to produce the "negative" results. It is literally one of the only such published studies out there, yet many folks refer to the results of it like they were extracted straight from the Dead Sea Scrolls. Meanwhile, Asians have been eating soy for years and outliving us “fat and happy" Americans by a decade or two without any overt testosterone, estrogen or thyroid issues.

Personally speaking, I find it so ironic that most anti-soy zealots base their entire stance on these ridiculous studies done on animals. Meanwhile, we have an epidemic of heart disease, cancer and a ton of other maladies in our world that are directly and unequivocally attributable to animal product consumption, based on human evidence. It’s no surprise that most of these supposed “experts” who are the loudest anti-soy proponents will turn around and recommend a battery of animal products for your good health. C’mon, people!

So let’s address a few of these issues. But first, let’s make a fundamental distinction. The old stand-bys like tofu, miso, tempeh, and tamari have a rich history as a healthy part of the classic plant-based diet as exhibited by many of the world’s healthiest cultures. For example, these kinds of soy products comprise over 10% of the Okinawan’s diet, and these folks remain among the most long-lived on the planet. Considerably more under the microscope, however, have been the multitude of soy-based animal product substitutes like soy milk, soy burgers, soy cheese, etc., and this is largely where the controversy has been directed. So let’s look at a few of the most popular anti-soy contentions and get to the real bottom line here.

Claim: That soy contains toxins that block the action of enzymes required to digest protein, ultimately having a negative affect on protein assimilation.

The claims go on to purport that these toxins stunt growth, cause cancer and enlarge the pancreas. But again, these results have only been established in tests on animals, and these tests involved massive amounts of soy. There is still no precedent that this is the case with humans. And as for soy’s trypsin inhibitors, which at certain dosages may have a negative effect on an animal’s pancreas, there is no science to support that this is the case where humans are concerned. Besides, other types of beans, as well as veggies from the cabbage family, have similar trypsin inhibitors, but no one is squawking about them.

Claim: That ingestion of soy inhibits mineral absorption.

Yes, just like nuts, seeds, grains and other beans, soy contains a fair amount of phytates. And yes, high amounts of phytates can indeed affect mineral absorption. But there’s just one problem with this theory. You would have to eat a crazy amount of soy (and not much else) to jack up your phytic acid levels to the extent needed to inhibit mineral absorption. Additionally, this theory is weakened further when applied to fermented soy products, because the fermentation process reduces phytic acid levels by one-third. Next…

Claim: That soy negatively affects thyroid function.

Here’s another one that’s often volleyed around the campfire without the full story being told. Soy contains food compounds called goitrogens, which have been known to interfere with thyroid function. Of course, other super healthy foods like millet and cruciferous veggies have these compounds, as well, so it’s not so much an issue exclusive to soy, although that’s where the attention is usually diverted.

By the way, this claim likely originated back in the 50’s and early 60’s when several cases of goiter popped up in babies who were fed infant formula derived from soy flour. Of course, once an adjustment was made to the formula in the 60’s - where soy protein isolate was used instead and extra iodine was added - there were no more cases reported.

The reality is, these goitrogens can cause trouble for the thyroid, either because a thyroid disorder already exists, and/or there is a deficiency of iodine in the diet. But it would be an stretch to say that reasonable consumption of soy was the actual cause of these thyroid problems, as some folks contend. Further evidence of this is in the many Asian countries where both soy and iodine intake is high, but hyperthyroidism is rare.

Claim: That soy can cause cancer.

One of the most impressive studies ever done on this subject was a collaborative effort between the American Institute for Cancer Research, and their international partners, the World Cancer Research Fund. In 1997, these folks did some serious homework on the relationship between soy and cancer. They referenced more than 4500 studies and included over 120 peer reviewers and contributors, which involved participants from the U.S. National Cancer Institute, the International Agency on Research in Cancer and the World Health Organization. Their ultimate findings were that as little as one serving of soy per day actually reduced the risk of cancer. This is quite a stretch from “soy causes cancer.”

Regarding breast cancer in particular, a lot of the anti-soy hubbub is centered around the estrogen-like behaviors found in isoflavones, which is an active ingredient in soy that is more prominent in some soy products than others. As discussed earlier, estrogen tends to make things grow, so the concern around high amounts of isoflavones is that if a woman has a predisposition for breast cancer, or even cancerous tumors in her breasts, then soy could promote the growth ala estrogen. Granted, if a woman were to consume large amounts of the more concentrated isolated isoflavones, one could argue that this could be the case. Yet, in typical servings of regular soy products, the plant estrogens actually protect the body’s estrogen receptors. And let’s not forget: Japanese women, who typically enjoy a wide variety of soy products, have about one-fifth the rate of breast cancer that American women have.

Claim: That soy negatively affects testosterone levels in males.

Some of the most unfounded and whacked-out contentions surrounding soy hinge around this sci-fi notion that soy can create various “demasculinization” effects in males. Some of these supposed effects include reduced sex drive, increased body fat, enlarged breasts (!) and even shrinking testicles! (I couldn’t make this shit up, people…but apparently, other folks can.) Obviously, this is anti-soy propaganda at its most shameless, as there is simply no credible basis in truth for any of this.

So where are the origins of this madness? They are primarily with animals, in more absurd studies. It appears that if you overload certain critters like mice with a ton of soy, the pro-estrogen effects of the above-mentioned isoflavones can affect the animal’s testosterone levels. But again, this is totally irrelevant where humans are concerned, both in terms of how humans assimilate soy and in the relative amounts of soy that are being used in these “studies.”

Additionally, there have been side-by-side studies done with meat-eating vs. soy-eating men where the meat-eaters had higher levels of testosterone. The spin on this has often been, “Ya see, soy reduces testosterone in men who consume it.” But the reality is, animal products and saturated fat are known to increase testosterone, so it’s more likely that the absence of all of the animal products (along with the increased fiber intake) kept the soy user’s testosterone levels in a lower, yet healthier range, in these cases. And this is a good thing, by the way, because in human studies, high testosterone levels have been directly linked to prostate cancer and other maladies. Just like with protein, the key is to have enough testosterone, but not too much. And every shred of science I’ve ever seen on the subject indicates that soy will not negatively affect your levels.

So what’s the bottom line here? Enjoy your soy, but do so in moderation, and always go organic when possible.


Bobby Rock is a seasoned health and fitness specialist and a renowned drummer, educator, producer and author of seven books. With certifications in personal training, nutrition and meditation, and a number of published writings on the subject of health and wellness, Bobby's unique approach to total mind/body fitness has gained him accolades among a wide cross-section of health enthusiasts. Check out for more info.


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