A streamlined stack of supplements designed to meet your most critical needs - Adapt Naturals is now live. Learn more

The Soy Ploy


Last updated on


Today’s article about the dangers of soy products is from Nourishing Our Children, an organization dedicated to supported learning, behavior and health in children through optimal nutrition. I encourage all parents to visit their website and read the “What Parents Need to Know” section. There is also a downloads section with free guides and briefing books available for download.

Although widely promoted as a health food, hundreds of studies link modern processed soy to malnutrition, digestive problems, thyroid dysfunction, cognitive decline, reproductive disorders, immune system breakdown, and even heart disease and cancer.

How could soy be linked to all this disease? Because the soybean contains many naturally occurring toxins. All legumes contain toxins but the problem with soy is that the toxins are found in very high levels and are resistant to the traditional ways of getting rid of them.

Long, slow fermentation (as in the traditional production of miso, tempeh and soy sauce) gets rid of the phytic acid and other digestive inhibitors but not the phytoestrogens in soy.

Myths about Isoflavones

One of the most common myths is that soy estrogens (isoflavones) are beneficial for your health. Isoflavones are the estrogen-like compounds occurring naturally in soy foods. They act as the plant’s natural pesticides, causing insects to become sterile. Research has shown that isoflavones can prevent ovulation and stimulate the growth of cancer cells. As little as 38 mg isoflavones per day (less than the amount found in 1 cup of soy milk) can result in hypothyroidism with symptoms of lethargy, constipation, weight gain and fatigue. The isoflavones in soy have been shown to cause reproductive problems, infertility, thyroid disease and liver disease in mice, rats, cheetahs, sturgeon, quail, sheep, pigs and marmoset monkeys.

Traditional versus Modern Soy Foods

It is important to distinguish between traditional and modern soy foods. In Asia, traditional soy foods were consumed in small amounts, usually as a fermented condiment. Traditional fermented soy foods include miso, soy sauce, tempeh and natto. Tofu was prepared by a precipitation process that gets rid of some of the anti-nutrients, and tofu was often then fermented. Tofu was usually consumed in small amounts in fish broth, which provided lots of compensating minerals and compounds that support thyroid function.

Soymilk underwent a very long preparation process to get rid of anti-nutrients and it was consumed with shrimp or egg yolk, ingredients that helped compensate for the many anti-nutrients that remained. Mostly a food for the elderly, it was sometimes given to nursing mothers but never to growing children.

Like what you’re reading? Get my free newsletter, recipes, eBooks, product recommendations, and more!

Problems with Soy Protein Isolate

Modern soy foods are very different. Most are made with soy protein isolate (SPI), which is a protein-rich powder extracted by an industrial process from the waste product of soy oil manufacturing. It is the industry’s way of making a profit on a waste product. The industry spent over 30 years and billions of dollars developing SPI.

Soy Protein Isolate is produced at very high temperatures and pressures. This processing does get rid of some of the anti-nutrients in soybeans, but unfortunately many of the proteins are denatured in the process, including lysine. That is why growing animals fed soy must be given a lysine supplement. In feeding studies, SPI caused many deficiencies in rats. That soy causes deficiencies in B12 and zinc is widely recognized; but the range of deficiencies was surprising.

Although SPI is added to many foods, it was never granted GRAS status, meaning “Generally Recognized as Safe”. The FDA only granted GRAS status to SPI for use as a binder in cardboard boxes. During the processing of soy, many additional toxins are formed, including nitrates (which are carcinogens) and a toxin called lysinoalanine. It was concerns about lysinoalanine in SPI that led the FDA to deny GRAS status for SPI as a food additive.

In spite of all these problems, SPI is the basic ingredient of soy infant formula and the FDA even allows a health claim for foods containing 6.25 grams SPI per serving.

The Dangers of Soy Infant Formula

Infants on soy formula can take in dangerously high levels of soy isoflavones. On a body weight basis, this can mean ten times the level that can cause thyroid suppression in adults after three months, and eight times the level that can cause hormonal changes in adults after just one month.

According to a Swiss report adult women consuming 100 mg isoflavones (about 2 cups of soy milk, or 1 cup of cooked mature soybeans) provide the estrogenic equivalent of a contraceptive pill.

This means for a baby that weighs 6 kg (or just over 13 pounds), 10 mg provides the estrogenic equivalent of a contraceptive pill. Thus, the average amount of soy-based formula taken in by a child provides the estrogenic equivalent of at least four birth control pills. Because babies are more vulnerable than adults to the effects of dietary estrogens, the effects could actually be much greater than that of four birth control pills.

Hence the statement, “Babies on soy formula receive the estrogenic equivalent of at least five birth control pills per day.”

Homemade Baby Formula

For adopted infants, or as a solution for mothers who aren’t physically able to breastfeed or who aren’t able to produce enough milk, we’d like parents to know that there are nutrient dense, homemade Baby Formula Recipes in the book Nourishing Traditions which have been used with great success by parents all over the world since 1995!

ADAPT Naturals logo

Better supplementation. Fewer supplements.

Close the nutrient gap to feel and perform your best. 

A daily stack of supplements designed to meet your most critical needs.

Chris Kresser in kitchen
Affiliate Disclosure
This website contains affiliate links, which means Chris may receive a percentage of any product or service you purchase using the links in the articles or advertisements. You will pay the same price for all products and services, and your purchase helps support Chris‘s ongoing research and work. Thanks for your support!


Join the conversation

  1. Hi, I do not see any citations listed after your given “facts”. Please disclose sources. Thank you.

  2. Hi Chris, I’m a little confused. You mention nitrate in soy products as a toxin/carcinogen but you’ve written SO much (and beautifully) about the nitrate/nitrite myth and our irrational fears of nitrates (and bacon!). So which is it?
    Cheers, Matt

  3. While I’m convinced by the arguments against soy, and I have a soy sensitivity myself, I’m hard pressed to find good data to support a lot of the anti-soy rhetoric. You mention “hundreds of studies” on the risks of soy, but you don’t list any in the references. Could you please provide a few. Thanks!

  4. Hi Chris

    I have a 17 year old with gynecomastia who had soy infant formula and is addicted to cow’s milk. We have switched to organic cow’s milk. I’m trying to connect the dots with regards to how his hormones got so out of whack and what to do to reverse this (provided that I could show that any such approach makes scientific sense, as my son wants to go down the conventional medical route of medication and surgery). Any pointers where to start looking? I understand if you’re unable to answer.
    Kind regards

    • Gynecomastia is a condition caused by an excess of estrogens in the male body which can be caused by estrogenic substances and diet. While phytoestrogens in soy and legumes can have an influence on hormone levels, normal intake alone is probably not enough. Polyunsaturated fatty acids (omega6&3) in seed oils can mimick and increase estrogen. Reducing seed oils from soy, corn, canola, cottonseed etc is important. Olive oil, butter, palm&coconut oil are monoun-/saturated fats and safer. Progesterone and pregnenolone are otc hormones which balance estrogen. There’s more information on RayPeat.com. If medication means aromatase inhibitors this is not too bad but if his diet/ lifestyle remains estrogenic than other problems might ensue.

  5. After reading this article I have to ask, do all of these warnings here apply to non GM soy products? I come from a country where GM foods are banned and most soy products are not GMOs. We even have unsweetened organic whole soybean milk, expensive but sounds positive. Is there anything wrong with non GM soy?

    • Everything listed here comes from normal non-gmo soy. It has never been good to eat much of it, GMOs might just be even worse.

  6. Thank you for this information. My 14 month old was diagnosed with milk and egg allergy at about 6 months old and confirmed again at 12 months. We were told to give him soy milk bc of the protein (which coconut milk and almond milk do not have enough of). What would you recommend instead of soy for a toddler unable to drink milk (he weaned himself right at 13 months…we do soy and also coconut milk with either pea protein or gelatin as supplements currently…and some leftover frozen breastmilk). Thank you!

    • What symptoms does your baby’s milk/egg allergies produce? Feeding pure cow milk to babies under 12 month is generally not recommended but in a later age shouldn’t be a problem. After 12 month a baby can eat almost all foods adults eat, prechewing helps. Meat & fish are the best sources of protein. Do you eat vegetarien?

  7. When I was 11 my mother put me on a vegetarian diet, ovo lacto with some chicken, I consumed about a pound of soy milk per day and also flax seed oil. 2 years later I was diagnosed with arthritis in my knees and morbus scheuerman, a deformation of the spin. Also I developed gynecomastia and male hypogonadism. In my early twenties I had a clinical depression. All these issues might have multiple causes but all of them relate to elevated estrogen, as far as I understand what Ray Peat says. Soy might have a good amino acid profile but the possible estrogenic toxicity seems to be underestimated.

    • I sympathize with your experience, as I went through a bout of crippling depression. However I question your link to soy’s culpability in this. soy is not a recent addition to the food chain. Plastics and intensive dairy production that leave estrogen in finished product are. to blame soy is short-sighted. I know of several individuals who developed gynecomastia on nothing but a good ol’ “meat and potatoes” diet. clearly more is at play than evil phytoestrogens in soy.

  8. I don’t personally consume much soy but I find some facts in this article to be misleading, whereas I usually find Chris Kresser to be well informed and reasonable. In particular, I question the claim by the WAPF that soy is equivalent to birth control pills. Isoflavones can more properly be called estrogen modulators, with both pro- and anti-estrogenic effects depending on the tissue. Besides this, they have a totally different structure than human estrogen and synthetic BCPs, so to claim that “soy equals X number of birth control pills” is a bit silly as there is no way to know a) What their overall estrogen activity is, and b) What that would equate to in milligrams of synthetic estrogen. Many other plants do contain isoflavones, so “estrogen” is everywhere in our environment. Dairy is one food source that actually has been shown to increase blood levels of estrogen.

    Secondly, I have traveled throughout Asia and note that people eat a lot of soy. Now it could be that in the past they ate less, but everyone I talked to, from chefs to foodies to professors of cultural studies all agreed that historically they ate a lot of soy. Perhaps this was their cultural bias, but I think not. And anyway, with how toxic the WAPF makes soy out to be, you’d think the population of Asia would be closer to zero instead of 4 billion or whatever it currently is.

  9. I have a PhD. in Biochemistry and currently a tenured associate professor at Ohio State University. I’d like to point out that this article is misleading and contains incorrect information. For example, Chris wrote: “This processing does get rid of some of the anti-nutrients in soybeans, but unfortunately many of the proteins are denatured in the process, including lysine. That is why growing animals fed soy must be given a lysine supplement.”

    The fact is, lysine is an amino acid, not a protein. Soy is naturally low in lysine (compare to milk and egg), an essential amino acid. This is the reason why additional lysine is added to animal feed. Also, proteins are denatured in all cooked foods. so there is nothing to be concerned about denaturation. In fact, proteins need to be denatured before they can be efficiently digested in your body.

    Chris also claimed that Asians eat soy products in small quantities and never gave soy milk to growing children. This is an absurd claim! Soy milk is widely consumed as part of the breakfast by the whole family throughout China. I know this because I am an immigrant from China.

    • Besides the fact of lysine being an aminoacid and information about the nutrition in China, where I don´t live, do you have any other information regarding soy being a good or bad food choice?

    • Hi Dage,

      You are correct about the lysine, but that is only a minor point in the article. I’m more worried about the isoflavones etc. Do you find fault with the reasoning there?

      I found the wikipedia article on soy milk very interesting, http://en.wikipedia.org/wiki/Soy_milk , it seems that soy milk has been made for quite a while in China, although it apparently wasn’t fed to children according to http://en.wikipedia.org/wiki/Soy_milk#cite_note-5 .

      Another question, isn’t the degree of denaturation important in how digestible a protein is? E.g. lightly denatured proteins can be cut by proteases, whereas heavily denatured proteins are less digestible? So industrial soy milk might be less nutritious than traditional soy milk? (ignoring the additives)

      • Hi Wout,

        I think there is sufficient evidence to show that isoflavone from food is safe for adults. Its supposed damage to infants is exaggerated by critics. Soy-based baby formula exist for a reason, i.e, to feed infants with lactose intolerance. It is irresponsible to advocate banning soy-based formula.

        I am not aware of any restrictions on soy milk usage in China. Not only soy milk, but also all kinds of tofu products (not just fermented ones!) are widely consumed in China and Japan. Immature soybean is also consumed as a delicacy in the form of edamame.

        To also answer Rafael’s comments, whether you live in China or not is irrelevant. Obviously if soy is that bad, how come the bad things haven’t happened to people living in the regions with widespread consumption of soy? This is a dilemma that Chris unfortunately chose to resolve with incorrect information.

        Finally, when you heat your food to the boiling point, proteins are all denatured. It is not true that half-denatured proteins are easier to digest. As long as you don’t burn your food, you don’t over-denature the proteins. In fact, slowly cooking meat causes proteins in connective tissues (such as collagen) to break down, aiding digestion. I don’t think that industrial soy proteins are heated at higher temperature than conventional cooking. In terms of digestibility, it is better than eating whole soybeans.

        Btw, I found that my earlier post actually contained an error. Soy proteins are not low in lysine. In fact soy is a complete protein with nutrition value equivalent to milk and egg. I was misled by Chris’ article. The main ingredient in animal feed is corn, which is deficient in lysine. This is the reason why lysine is added to animal feed. It has nothing whatsoever to do with the nutrition value of soybean meal.

        • Hi Dage.

          I think there is sufficient evidence to show anything you want about soy and for me, that´s the problem.

          I´m not a PhD, nutritionist, doctor, not even linked to science, so I have to make my evaluation in a simpler way (maybe superficial to you): Why is soy consumption so controversial? Why so many scientists decide to attack the soy consumption on their studies? What do they gain doing that? Why soy?

          On the other hand, there´s a lot of money involved on defending soy. A whole industry. One of the biggest… I´ve read that many of the studies, that adverts the soy benefits, were sponsored or the authors are somehow linked to the soy industry and maybe that´s why some of the bad things caused by soy consumption are not widely reported. For each study showing harm, there is another one showing the benefits, and that causes… controversies. In a world where money is more important than public health, I prefer to be cautious.

          • My original post was only meant to correct obvious mistakes in Chris’ article. Mistakes are very common in this kind of food advocacy articles. This is why I occasionally found myself having the urge to write some rebuttals, for what it’s worth. However, I know people can be passionate about their believes, so I have no expectation to persuade anybody. You of course are free to choose what to believe and what food to avoid. It’s none of my business. There is no tradition of soy consumption in this country anyways. Plus, avoiding soy is only inconvenient for vegetarians, particularly vegans, by losing out on such an excellent substitute of animal proteins.

            Soybean products had been widely consumed in East Asia long before the soy industry came to existence, I noticed that Chris studied Chinese medicine. A usual argument for Chinese medicine is that it has been used for hundreds of years so it must at least be safe. The same logic applies to soy. I wonder why there is a double standard.

  10. This blog post is one of the most misleading and misinformed I’ve seen to date on the purported “soy controversy.” The overwhelming majority of research on soy intake and health strongly links soybean consumption to protection from heart disease, cancer, and cognitive decline in a predictable, dose-responsive manner. Any possible goitrogenic (read: thyroid-suppressing) effects of soy are easily curtailed through adequate iodine intake. The balance of existing evidence weighs heavily in favor of soybean consumption, including several well-established Cochrane Collaboration systematic reviews with pooled sample sizes in the millions, and a rigorous ranking of scientific research methods. Read the literature carefully, and you’ll find that those isolated studies that Kresser “cites” here, linking soy to possible negative health outcomes, were primarily performed in Asia, namely Indonesia, where the majority of soy consumed is as tofu which, in those respective countries, is preserved with formaldehyde. No wonder it was so heavily associated with health decline. I suggest Mr. Kresser pore through the literature with a fine-toothed comb before publishing ill-informed articles. To the readers of this post, I suggest you consult with Dr. Michael Greger, MD at http://www.nutritionfacts.org for more credible nutrition information.

    • Goiterogenic substances in soy prevent the uptake of iodine by the thyroid. How does supplementing iodine resolve this problem? Why don’t you link some of these “well-established systematic reviews with pooled sample sizes in the millions, and a rigorous ranking of scientific research methods” instead of posting a link to an advocate of veganism?

  11. Comments such as:
    “The isoflavones in soy have been shown to cause reproductive problems, infertility, thyroid disease and liver disease in mice, rats, cheetahs, sturgeon, quail, sheep, pigs and marmoset monkeys.”

    MUST be cited. Shown by whom? I’m sick of reading advice on any side of the dietary debate that do not back themselves up. Without citations how am I to know where this information came from?

  12. Is the soy in multivitamins (e.g. Pure Encapsulations Nutrient 950 w/ vit K2) a concern?
    I do my best to stay away since it is a gluten cross reactive food that I am sensitive to.
    Just curious if it is not a problem when extracted from soy to make vit E in vitamins? I have not found any valid data for either side.

    The only good quality multivitamin that I can find that is soy free, etc. with Vit K2 and Folate. Is Dr. Ron’s Ultra Pure: Doc’s Best the next generation. It is a bit expensive.

  13. I just found this blog post explaining that moderate soy consumption is probably safe for post-cancer patients : http://www.naturalmedicinejournal.com/article_content.asp?article=377

    What strikes me is that the isoflavone dose they regard as safe and possibly beneficial is 10mg/day but that would mean 1/3rd cup? Odd. I also see that the only outcome studied is cancer, no mention of other health issues. It does note that soy consumption could be a proxy for a generally healthy diet.

    Another interesting bit is that rodents seem to process dietary isoflavones differently, it has worse effects for them vs humans. Possibly we’re adapted to higher isoflavone intake?

    Would love to read your thoughts on this.

  14. Do you happen to know of any studies of, or know of a link between, soy’s role in coeliac (celiac) disease. I sometimes wonder if soy caused me to become intolerant to gluten. After all, gluten issues were uncommon before soy became so widely used in the food industry…

    • I don’t know if soy would induce gluten intolerance, but I do know that wheat has changed quite a bit over the last 50 years. The wheat we eat today (at least in the US) has much more gluten than the ancient wheat varieties some humans have eaten for thousands of years. I’d bet that this new high-gluten wheat has more to do with the rise in celiac disease than soy.


    • I know someone who has celiac disease. He can’t eat most wheat products in the US but can eat most wheat products over in Europe, at least the places he went to in Europe, because the wheat there was from “heirloom” varieties which are low in gluten. The varieties that were bred and are mostly grown in the US are much higher in gluten content.

  15. All processed foods are poison; no surprise there.

    Aren’t the diseases from soy linked to GMO soy?

    • No, all soy has anti-nutrients and isoflavones. Many plants do, but they’re usually lost when processed. Soy is more resistant to processing (ie: fermenting/cooking) and has more of it than other plants. There are many plants which can be toxic or even deadly when eaten unprocessed/raw but are just fine when cooked or fermented. Soy is not one of those, there’s still too much left after processing.

  16. Hello,
    I’ve been a vegetatian for almost 20 years (more than half my life) and started drinking soy milk 24 years ago, when it was 1st (commercially) available. I have stuck to the same brand my entire life. I have gone for annual bouts of 4 weeks & sometimes evena little longer, when I travel to the USA. I didn’t gain any weight from drdinking soy milk, neither did I lose any weight because I ‘rested’ from drinking soy milk. The brand I drink is high in calcium, iron & B12. Just like milk from a cow, not everyone may be able to handle soy, but for me, I definitely feel it’s the healthy fit for me.

    • Hi Melissa,

      I’m not sure why you mentioned weight gain or weight loss in regards to consumption of soy milk. Soy is low in calories so it stands to reason that it wouldn’t cause weight gain. However, that doesn’t mean it’s a benign food at all.

      For more on the dangers of soy, see this article. You can also read The Whole Soy Story, by Kayla Daniel, Ph.D. The introduction is available online here.


      • Hi Chris,
        I think he linked the gain weight to thyroid dysfunction caused by soy intake. My mother and sister are vegetarian but unfortunately they are overweight/obese respectively.

      • Chris – here is a quote from your very own article above…which indeed makes a reference to weight gain.

        “As little as 38 mg isoflavones per day (less than the amount found in 1 cup of soy milk) can result in hypothyroidism with symptoms of lethargy, constipation, WEIGHT GAIN and fatigue.”

        So your response here to Melissa comes across as very ignorant since you have questioned and almost belittled her reference to weight during periods of time of soya milk consumption.

        Your comment alone has challenged my judgement of this entire post.

        I think you should pay more attention to the information you are providing to such a large audience before you respond so dismissively to one of your readers.
        What an oversight.

  17. I’m trying to find out information for my daughter who recently is suffering from depression that is more than teenage angst. She’s been vegan for a year and a half and has lived on a diet very heavy in soy-based products. I’m suspecting that the soy is causing some of her depression. Is there anything out there that supports this?

    • Not only the soy, but the deficiency in amino acids from animal protein. Low tryptophan = low serotonin. There’s no such thing as a healthy vegan. Try to convince her to at least try some eggs and cheese to begin with and see if she feels better… Good luck!

    • Life is really tough. Being a teenager is even harder. There are so many struggles that we face in the modern age. So many directions and manipulations and conflicts and so on….depression is a spiritual response and probably more connected with feelings and emotions than diet.
      That said – iron deficiency can cause feelings of depression through the lack of energy and correct nutrition.
      Being vegan isn’t bad or wrong – but you must learn enough about nutrition to make sure you’re creating a balanced diet for yourself with supplementing the “missing” bits.

      P.S…The person who’s responded with “there is no such thing as a healthy vegan”????? That is bold and ignorant isn’t it?
      I am not a sports enthusiast myself but just for example – I struggle to understand how these incredible athlete’s are “unhealthy”…..http://www.greatveganathletes.com/

  18. Check out the “Soy Alert” link above for many articles with references and studies about the dangers of soy.

  19. quite alarming all the weight gain and such. do you have any sources on that? i must be superman (or woman with all the estrogen in my body) considering i lost about 10 pounds of body weight with a slowed down thyroid gland.