Debunking the myth that soya is good for health

Soybean the “cheap protein”

Soy is very cheap to produce1,2 and offers a good amount of proteins3. From a business point of view this is great. From a health and social point of view, you will see later that it is rather a failure.

My opinion on soy

Soy is not a “healthy” food. It is a cheap source of proteins that has a good marketing machine behind it. Twelve years ago I read in details about soy plants and found that it was defending itself very well from insects with the various toxins it could produce. My guess back then was that it should not be consumed on the long-term. I was pretty sad hearing people telling me proudly they were drinking soy-milk for health-related considerations.

In the last few years I’ve seen circulating some studies indicating that soy was indeed not that healthy and that some of the toxins it produces are not destroyed by cooking, confirming my suspicions. My opinion on soy is that it is not evil and I wouldn’t be afraid to eat some but I would not label it as a health-food and not recommend its protein extract.

Natural plant defenses and toxins in soy

<< Unfermented soy contains “anti-nutrients” including estrogens, goitrogens, oxalates, phytates, protease inhibitors, saponins and soyatoxin. >>4

<< The protease inhibitors in soybeans are not only more numerous than those found in other beans and foods, but more resistant to neutralization by cooking and processing. >>5,6 Protease inhibitors can be a problem on the long-term.

In general many plant lectins can be broken down to a certain extent with cooking, and often almost all with a pressure cooker. The main problematic plant lectin in soy is agglutinin which can be reduced by fermentation and cooking. Some examples of plant lectins that cannot be broken down in a pressure cooker are wheat, oat, rye and barley [ref The Plant Paradox book, p180, 181].
<< Soybean agglutinin (SBA) is a major anti-nutritional factor that represents 5–7% of the soybean. (…) Although the biological activity of SBA can be reduced by proper heating, a considerable quantity is still found. This residual SBA can affect intestinal health by influencing intestinal structure, barrier function, the mucosal immune system, and the balance of the intestinal flora.  >>

There is also a toxin in soy called soyatoxin that was found in 1994 and that appears to be highly toxic to mice. The researchers concluded that it is <<important to gather more information concerning its nutritional value, and to develop ways to counteract any detrimental effects. >>7

I could do more or less the same for a lot of edible plants, and this alone should not be a basis for indicating if it is “healthy” or not. What we need is scientific studies on humans that shows what happens when you eat the whole food – and not just an extracted single-component – over a long period of time.

Scientific studies on soy that show negative effects

Brain aging and midlife tofu consumption.
<< CONCLUSIONS: In this population, higher midlife tofu consumption was independently associated with indicators of cognitive impairment and brain atrophy in late life. >>

Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. << CONCLUSIONS: These data suggest that higher intake of soy foods and soy isoflavones is associated with lower sperm concentration. >>

Dietary soy protein and isoflavones have no significant effect on bone and a potentially negative effect on the uterus of sexually mature intact Sprague-Dawley female rats << Conclusion: These results suggest that dietary isolated soy protein and isoflavones have no effect on bone and the vagina during premenopausal period, but may have an adverse effect on the uterus.>>

There is a great lack of human studies on whole soy / tofu. Any nutritional study on humans are really costly to make or never really conclusive since they are observational studies.

These are the great problems I find with nutritional studies on soy (and in general) :

  • Participants are not randomly chosen; then the individuals themselves decided to eat and food choice is usually associated with other confounding cultural habits that affect health;
  • Participants retrospectively report on what they ate (retrospective studies);
  • Studies in humans span less than a single generation.
  • Most studies are on partial soy extracts.
  • No studies compare organic versus non-organic soy unfortunately.

Bad science in pro-soy articles

Let’s go directly on the Soyfoods Association of North America website in a page where science is supposed to be found, let say in the Men’s health page where there is a lot of references : (viewed on August, 2014). It says << Human studies have found that males who consume soy have not had changes in sperm count, sperm quality or sperm motility. >> However if you take the time to look at the reference (Chavarro JE, Toth TL, Sadio SM, Hauser R. Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Hum Reprod 2008;23:2584-90.) which talks about semen quality, you will see the following conclusion in the cited study (which is the same study I previously cited in the previous paragraph!!) : << CONCLUSIONS: These data suggest that higher intake of soy foods and soy isoflavones is associated with lower sperm concentration. >> (and that’s the only conclusion) (Chavarro JE & al). Basically the only citation the Soyfoods association took is a partial extraction of results that suits their own interest and that goes against the study’s own conclusions.

Be careful about industry-funded articles!

Soy Isoflavone

Soy and cancer

There is no link between cancer and soy. It is a plant from nature that has been eaten for thousands of years and human studies have not found a link between cancer and soy. On the contrary, Asian studies showed that soy was beneficial against cancer. My personal theory on that is that soy naturally contains phytic acid12 which is an iron chelator; and higher iron levels are associated with cancer; thus lowering of iron lowers cancer risks.

However studies in the US have not shown this beneficial trend. I didn’t find the explanation why, but my hypothesis – for what it is worth – is that either (i) Asians handle soy better and/or (ii) the soy grown in the US is different (pesticides), (iii) Asian eat fermented soy and whole plant instead of soy extracts, or (iv) GMO soy impacts the iron homeostatis. Note that in  the US (along with UK and Canada) food is fortified with iron.

I will add a personal thought that it is time that scientists begin using organic versus non-organic version of food during testing to eliminate the effect of pesticide residues. My source is directly from which I believe we can trust to be impartial toward the industry and in the best interest of the fight against cancer :
<< (…) a recent study combined data from 14 epidemiologic studies on this topic and found that in Asian countries, women who ate the most (compared to the least) soy isoflavones had a 24% lower risk of developing breast cancer, while there was no association in Western countries such as the U.S. >> and << Bottom line: Even though animal studies have shown mixed effects on breast cancer with soy supplements, studies in humans have not shown harm from eating soy foods. Moderate consumption of soy foods appears safe for both breast cancer survivors and the general population, and may even lower breast cancer risk. Avoid soy supplements until more research is done. So, enjoy your occasional tofu stir-fry or tofu burger – they are unlikely to increase your risk of breast cancer and, on balance, are some of the healthier foods you can eat! >>

Soy and Thyroid Function

<< Goitrogens, by definition, are substances that suppress the thyroid gland by interfering with thyroid hormone production. (…) Soy is one particular goitrogen that is especially detrimental for Hashimoto’s patients. (…) Soy has been linked with the development of autoimmune thyroid conditions, and children fed soy formula were almost three times more likely to develop anti-thyroid antibodies as compared with breast-fed children >> In the book Hashimoto’s Thyroiditis by Izabella Wentz, PharmD, FASCP and Marta Nowosadzka, MD., page 82. I am however very doubtful of the odd ratio of three times more likely as they probably didn’t take account of the added iron in infant formula. Elevated iron has been known for many years to increase incidence of thyroid injury followed by development of antithyroid antibodies and hypothyroidism[ref].

Soy and Autoimmunity

2020. Reaction of Lectin-Specific Antibody with Human Tissue: Possible Contributions to Autoimmunity>/span>
<< Wheat germ agglutinin-specific antibody was the most reactive with the tissue antigens (37 tissues out of 62), followed by red kidney bean phytohemagglutinin-specific antibody (20), soybean agglutinin-specific antibody (20), and peanut agglutinin-specific antibody (15). This reaction between anti-lectin antibodies and many human tissue antigens may be due to possible molecular mimicry and cross-reactivity. >>
<< The reaction of anti-lectin antibodies with human tissue components and their detection in RF-positive samples may describe mechanisms by which the production of antibodies against undigested lectins may contribute to the pathogenesis of some autoimmune diseases. >>

Dr. Steven R. Gundry, wrote a wonderful book on the subject of lectins and autoimmunity. I suggest anyone interested in nutrition to read it.

Soy and Allergies

The US Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA) identifies soybeans as a “major food allergen.”

The Canadian Food and Drug Regulations have very similar provisions for the labeling of soy as a food allergen.

Highly refined soy oil however seems not to require labeling as a food allergen and does not appear to be associated with allergic reaction.

Plant biologist Mark Olson mentions in a Discovery Channel documentary that << (…) soy tends to be a fairly highly allergenic food. It causes allergies easily in many people. We think that this is because of the form that some of the proteins are in soy. >>

At 1:06:40, hear Dr. Garth Nicolson, PhD say that NT factors supplements created from soy can be safe even for people with allergies to soy.

How soy is used

Nearly all soybeans are processed for their oil. What remains is high-protein fibers9.

83% of the worldwide production of soy is used to feed animals10.

This means they first extract the oil, then process the rest into protein meal. If you think about it for a minute, that means most of the soy proteins sold on the market have chemical solvent residues from the oil extraction process.

Soybean production has exploded compared to other crops


More bedtime reading can be found there :

The truth is out there

The DARK Side Of Soy – America’s Favorite ‘Health’ Food by Kaayla T. Daniel

Should we worry about soya in our food? by Felicity Lawrence

The Shadow of Soy Or, How I Stopped Loving and Learned to Worry About the Bean by Sean Carson

Soy Protein Sucks! by Author L Rea


My goal is to tell you that putting the same thing in your diet weeks after weeks, for more than a year is generally not a good idea unless it is really good – and soybean is not in that category. Soybean does not stand out from a health point of view. It does stand out from an economical point of view and as an industrial alternative to petroleum in the production of goods. The beneficial health effects reported are from fermented soybean.


1. United States Department of Agriculture, Impacts of Higher Energy Prices on Agriculture and Rural Economies. [Online]. Available from: [Accessed 3rd August 2014]. (Figure 2.1 and 2.2)

2. Big Picture Agriculture, How Higher Energy Prices Will Affect U.S. Agricultural Production. [Online]. Available from: [Accessed 1st August 2014].

3. Xun Yao Chen, Why growing corn and soybean demand helps fertilizer stocks. [Online]. Available from: [Accessed 22th August 2014]

4. Cary Neff, The Benefits of Fermented Soy. [Online]. Available from: [Accessed 22th August 2014].

5. Kaayla Daniel, Plants Bite Back. [Online]. Available from: [Accessed 22th August 2014].

6. Daniel, Kaayla T. The Whole Soy Story (New Trends, 2005) 195-212.

7. Vasconcelos IM, Trentim A et al. Purification and physiochemical characterization of soyatoxin, a novel toxic portein isolated from soybeans (Glycine max), Arch Biochem Biophys, 1994, 312, 2, 357-366.

9. North Carolina Soybean Producers Association, How Soybeans are Used. [Online]. Available from: [Accessed 22th August 2014]

10. My calculation is as follow : 85% is crushed into meal, and 98% of this meal is fed to animals: 0.85 * 0.98 = 0.833, thus 83%. Raw numbers from :




Annexe 1 – These tactics could be used by industry funded article to get push their own agenda

  • Reduce the research scope, for example by reducing the length of the study to a few months instead of two or more generations.
  • Testing a single nutrient in an in-vitro research, e.g. on isoflavones, instead of a study on complete plant on human, then extrapolating that the full product is good and should be recommended by health practitioners.
  • Cherry-pick only some findings from a study and re-write a new article with only those – sometimes going against the conclusion of the original article. This is just like in the example above about by the Soyfoods Association of North America website. The industry just says that sperm mobility is unchanged but “forgets” to mention about the reduced sperm concentration.