Soy: 13 Reasons Why Soy Is The Worst Food In The World

I'm going to say it - Soy is the worst food in the world.

It's horrible stuff, and yet we consume so much of it.

Forget about sugar, don't worry about cholesterol, soy - and it's countless related products - should be public enemy number one when it comes to health damaging foods.

I'll explain why this is the case soon, but before you think to yourself that only hippie vegans eat soy, think again. Soy is everywhere. And you will be consuming in.

In fact, Dr Joseph Hibbeln from the National Institute of Health has estimated that soybeans - in the form of soybean oil - account for 10% of the typical Americans caloric intake! (1)

And even if you avoid the main soy offenders - such as soybean oil, tofu and soy milk - soy and it's processed derivates are commonly used in packaged snacks, chocolate, sports drinks, snack bars, protein bars oh and gluten free products (guess what flour they use when they remove wheat flour... that's right, soy flour).

When I refer to 'Soy' as a food, I am referring to the following food products:

  • Tofu (Made from soybean milk curd. A common staple in a vegetarians diet)
  • Soy sauce (found in sushi outlets all around the world)
  • Soy milk (misbelieved to be a  ‘healthy alternative to traditional milk)
  • Soy flour (found in most processed foods, especially gluten free products)
  • Soy protein powder (found in most sports bars, sports drinks and protein powers)
  • Baby formula (many low cost infant formulas contain soy)
  • Edamame (soybeans served at many Japanese restaurants)
  • Soy 'meat' (pseudo bacon, sausages and hamburger patties made with soy)
  • Soybean oil  (commonly used by restaurants and food manufactures across the world)

Before you run off to the pantry to check all your ingredients labels, let's look at why Soy is so toxic, and why you need to avoid it at all costs.

1. 82% of Soy Is Genetically Modified

The first Genetically Modified Organism (GMO) was developed by Monsanto (the same company that brought the world Glyphosate) in 1994.

Today it is the worlds most grown GMO crop. With 94% of Soya Bean crops grown in the USA being GMO Soy (2). And 82% of all soy grown world wide being GMO (3).

GMO soy adoption in the US - Source USDA

Pretty much, unless you're extremely (and I mean extremely!) pedantic about your diet, you are most likely consuming soy in your diet and that soy is no doubt GMO.

What does this mean for our health?

Well firstly, GMO Soy is designed to be 'Round-Up Ready'. I'll cover this in more detail below, but in a nutshell it means farmers can spray Glyphosate (Roundup) on the crop without the soy being affected. In turn, the residue count of glyphosate in soy is very high (whereas non GMO soy had zero glyphosate contamination (4))

Secondly, studies have shown that GMO soy is nutritionally inferior compared to its non-GMO counterpart (4).

Thirdly, you're eating a genetically engineered organism, with all the risks and issues that these unnatural crops bring to our health.

I don't want this article to be about the dangers of GMO food (I'll save that for another day), but GMO Soy has been linked to sterility, infant mortality and abnormal growth.

For more on the dangers of ingesting GMO food I recommend the book Seeds of Deception by J. Smith. 


2. Soy Contains Extremely High Levels of Toxic Pesticides

Expanding on my point above, GMO Soy has been tested to contain glyphosate residues averaging 11.9 parts per million, with a maximum reading of 20.1 ppm. 

When in 1999 Monsanto - the manufacturers of Roundup reported that in their tests the highest level of glyphosate contamination in GMO soy was 5.6ppm - a level that they claimed was 'far higher than typically found' and 'extreme' (6).

To put this figure in perspective, New Zealand has a glyphosate tolerance level for fruits of 0.01ppm

You're probably thinking 'so what?'. This is where things get scary.

Glyphosate - the most used herbicide in the world - is extremely toxic to our bodies.

I cover this in great detail in my article Glyphosate: Why You Need To Eat Organic, but here are a few snippets from that article:

  • Glyphosate exposure is linked to poor liver health. 
  • Glyphosate was also found to alter the expression of more than 4000 liver and kidney genes.
  • Numerous studies have shown that glyphosate as an antibiotic can alter the gut microbiome, which in turn can lead to such as gut dysbiosis.
  • Roundup can cause bacteria to become resistant to antibiotics. 
  • Roundup caused a decrease in sex hormone production 
  • Glyphosate increased estrogenic activity in the body 
  • World Health Organization’s International Agency for Research on Cancer (IARC) re-classified glyphosate as “probably carcinogenic to humans.” 
  • Use of glyphosate was linked to an increase in miscarriages and premature births in farming families. 
  •  A public health crisis has emerged around Roundup as government reports have confirmed high rates of cancer and birth defects in areas where people are exposed to spraying. 

(Source - Glyphosate: Why You Need To Eat Organic)

Poison being sprayed on roundup-ready crops

Even more scary is the study that found glyphosate contaminated soy beans fed to pigs led to 'congenital malformations' (7). The authors noted:

All organs or tissues had glyphosate in different concentrations. The highest concentrations were seen in the lungs and hearts.
These piglets showed different abnormalities as ear atrophy,spinal and cranial deformations, cranium hole in head and leg atrophy; in one piglet one eye was not developed, it had only a large one. Piglets without trunk, with elephant tongue, and female piglet with testes were also present.


 3. Soy Contains A Compound Linked To Hormonal Disruption

Soy contains isoflavones, a type of phytoestrogens that has been linked to disrupted endocrine function.

Previously, these isoflavones were thought to be beneficial for our health. So much so that:

"Protein Technologies International (a division of Dupont), requested a health claim for isoflavones, the estrogen-like compounds found plentifully in soybeans, based on assertions that “only soy protein that has been processed in a manner in which isoflavones are retained will result in cholesterol-lowering.”  

However, later on, the FDA rewrote the PTI's petition:

"...removing any reference to the phytoestrogens and substituting a claim for soy protein, a move that was in direct contradiction to the agency’s regulations.

The abrupt change in direction was no doubt due to the fact that a number of researchers, including scientists employed by the US government, submitted documents indicating that isoflavones are toxic. Many letters were written in protest, expressing concerns about mineral blocking effects, enzyme inhibitors, goitrogenicity, endocrine disruption, reproductive problems and increased allergic reactions from consumption of soy products."

Today the FDA requires warnings on estrogen containing products, but not soy products.

A review looking at Soy Isoflavones concluded that:

Significant therapeutic properties have been generally attributed to soy isoflavones, but most of the claims have been poorly, or not at all, confirmed by well designed clinical trials. Such is the case of the purported role of soy isoflavones in reducing plasma cholesterol levels. This link is now not supported by many authors or by appropriately designed clinical studies.

Disturbing data have been reported on potential negative effects of soy isoflavones on cognitive function in the aged, particularly relating to tofu intake. Recent studies have finally indicated a potential role for soy isoflavones in inducing chromosomal changes in cells exposed in vitro and potentiating chemical carcinogens.

Available data do not appear to unequivocally support beneficial effects of soy isoflavones, and warn against their wide use, in the absence of satisfactory clinical findings. (8)

The studies showing the harmful effects of isoflavones are numerous, Weston A Price has a great resource listing all these studies in their article 'Studies Showing Adverse Effects of Isoflavones, 1950-2013'. I highly recommend reading through this document.

4. Eating Soy Affects Estrogen Levels

The phytoestrogens found in soy mimic the effect of estrogen in the body, and can alter a woman menstrual cycle. 

In fact, some woman notice that regular consumption of soy milk alters their menstrual cycle.

If a cup of soy 'milk' alters womans hormones, what is it doing to men?

A paper in the Canadian Medical Association Journal looked at male children's exposure to diethylstilbesterol (DES), a synthetic estrogen that has effects on animals similar to those of phytoestrogens from soy. Their findings? The boys had testes smaller than normal on maturation (9). 

And we have an n=1 study where a 19 year old boy consumed large dose of soy for a year. He lost his libido and had erectile dysfunction problems along with lower Testosterone levels (which returned to normal after a year of ditching the soy intake) (10). Though it needs to be remembered this had a study size of one!

In summary, it’s important to know that this topic is still hotly debated, and there are a lot of inconsistencies in the data. We do know that soy contains phytoestrogens and does have a lot of biological and hormonal affects on the body. 

5. Soy is Extremely High In Inflammatory Poly-Unsaturated Fatty Acids 

Poly Unsaturated Fatty Acids (PUFAS) are extremely unstable fats and oils. Omega 3 and Omega 6 fats are both examples of PUFAs.

When these fats are consumed, they cause increased inflammation in the body. Worst, because they are so unstable, heat and light exposure can also set off the chain reaction known as oxidation.

I go into much more detail on all things PUFAs in THIS article, if you are unfamiliar with PUFAs and the damage they can do to our body I encourage you to read it.

Unfortunatley, most cooking oils used today are PUFAs. Canola oil and soy bean oil being the main offenders.

PUFA rich cooking oil

Consumption of PUFAs is linked to:

  • obesity
  • cancer
  • inflammation related illnesses
  • heart disease
  • immune function issues

Source: PUFAs:

While some health experts believe excess PUFAs in our diet are the biggest contributor to our modern health issues. 

The problem is food manufacturers and restaurants use large amounts of Soybean oil because it's so cheap. Unfortunatley, it's also extremely high in the easily oxidised, highly inflammatory omega 6 PUFA.  Soy bean oil contains 57% PUFA fats. In comparison Olive oil contains 8% PUFAs and butter only 3%.  

6. Soy Damages The Brain

In the article titled 'Soy and the Brain' the author shares evidence of Soy consumption leading to cognitive impairment and increased risk of alzheimers disease.

The article reads:

In a major ongoing study involving 3,734 elderly Japanese-American men, those who ate the most tofu during midlife had up to 2.4 times the risk of later developing Alzheimer’s disease. As part of the three-decade long Honolulu-Asia Aging Study, 27 foods and drinks were correlated with participants’ health. Men who consumed tofu at least twice weekly had more cognitive impairment than those who rarely or never ate the soybean curd.11, 12

“The test results were about equivalent to what they would have been if they were five years older,” said lead researcher Dr. Lon R. White from the Hawaii Center for Health Research. For the guys who ate no tofu, however, they tested as though they were five years younger.

What’s more, higher midlife tofu consumption was also associated with low brain weight. Brain atrophy was assessed in 574 men using MRI results and in 290 men using autopsy information. Shrinkage occurs naturally with age, but for the men who had consumed more tofu, White said “their brains seemed to be showing an exaggeration of the usual patterns we see in aging.”

7. Soy Lowers Testosterone, Sperm Count and Testicular Size

There have been numerous animal studies showing soy consumption in early life and its negative affect on testicular size (9, 13), lower testosterone (14), and decreased testicular expression of steroid hormone receptors (15). Though it should be noted that there are some inconsistencies across studies.

There are also studies that show soy consumption in humans leads to lower sperm count (16). A 2013 study compared the hormone production of men drinking soy protein to those drinking whey. After two weeks they found the soy drinkers had lower testosterone levels and higher cortisol levels (17).

But it's not just soy milk that causes lowered testosterone. Two studies looked directly at soy vs testosterone levels. The first looked at consumption of soya flour on testosterone levels. They found that those who ate the soy flour lowered their T levels during the study period (18).

And the second study looked at the consumption of soy protein isolates (powder) in healthy men. They found that testosterone levels decreased upon consumption of soy powder (19).

8. Soy Has Thyroid Disrupting Properties

I've explored the links between soy consumption and endocrine (hormone) function - in particular sex hormone production. But the evidence is clear that soy consumption also impairs thyroid health

Below is an excerpt taken from the Weston A Price article on Soy:

"... a report from the Institute of Endocrinology in the Czech Republic correlates markers of thyroid disease with soy phytoestrogen levels. High levels of soy isoflavones in the blood of 268 children without overt thyroid disease correlated with high levels of thyroglobulin autoantibodies and small thyroid gland size.

While “only modest association was found between actual phytoestrogen levels and parameters of thyroid function,” the researchers warned that “even small differences in soy phytoestrogen intake may influence thyroid function,” ending with the disclaimer, “which could be important when iodine intake is insufficient” (Clin Chem Lab Med. 2006;44(2):171-4).

Another recent report found that “Soy formula complicates management of congenital hypothyroidism.” Infants fed soy formula were found to have prolonged increase of thyroid stimulating hormone (TSH) compared to infants fed non-soy formula (Arch Dis Child. 2004 Jan;89(1):37-40). 

Soy beans contain goitrogens. Goitrogens block natural thyroid hormone synthesis in the body and also impact iodine status (iodine is important for optimal thyroid health).

Research has shown that rats fed soybean flour for 7 weeks led to their thyroid gland growing four times its usual size. Plus the researchers commented that the iodine requirements of the rat when on this (soybean flour) diet doubled the normal amount (20).

This was backed up by another animal study (this time on chicks). Which found a doubling of soybean oil of their diet (from 30% to 60%) led to improper functioning of thyroids causing goiters in the chicks (21).

Finally, there was a rather small investigation that looked at 3 children who had an enlarged thyroid gland (goiter). These children had been consuming soy milk. When this soy milk was removed from their diet (and replaced with cows milk) their goiters grew smaller in size (22). 


9. Soy Blocks Absorption of Vital Minerals

In my article titled 'What You Need To Know About Supplements ' I explained how the typical american diet was lacking in vital nutrients, and how many of us were malnourished.

This malnourishment was due to 3 causes: poor diet choice, poor soil and crop quality, and eating foods that blocked vitamin and mineral absorption.

Soy is related to the last point (though I would argue it is also tied to the first point as well!)

Soybeans contain phytic acid, oxalates, enzyme inhibitors (trypsin) and saponins. These are commonly referred to as 'anti-nutrients' as they block or impair nutrient absorption in the body whilst also impairing the bodies ability to digest protein. 

The problem is two fold. The trypsin inhibitors reduce protein digestion, meaning the body cannot extract all the vitamins and minerals from the food you have digested.

Secondly, the anti-nutrients such as phytic acid found in extremely high levels in soy, bind to certain metal ions including magnesium, zinc, iron and calcium - blocking absorption by the body.

Topping it off, soy foods increase the bodies requirement of vitamin d and iodine. You can see how a diet high in soy is going to cause nutrient deficiencies.

If you still don't believe that consuming soy (even if it's organically sourced) can leave you lacking key nutrients, have a read of these four studies:

  1. The inhibitory effect of soy products on nonheme iron absorption in man. Findings: " The soy products tested in this study have a pronounced inhibitory effect on the absorption of nonheme iron."
  2. Soy protein, phytate, and iron absorption in humans. Findings: "It is concluded that phytic acid is a major inhibitory factor of iron absorption in soy-protein isolates "
  3. Bioavailability of the calcium in fortified soy imitation milk, with some observations on method. Findings: "Calcium-fortified soy milk does not constitute a calcium source comparable to cow milk"
  4. A study on absorption and utilization of calcium, iron and zinc in mineral-fortified and dephytinized soy milk powder consumed by boys aged 12 to 14 years. Findings: Absorption of calcium, iron and zinc was lower in soy milk than it was in cows milk


11. Soy Consumption Is Linked To Increased Food Allergies

Everyone seems to have an allergy these days - peanut allergies, egg allergies, diary allergies... Is it because of the increased soy consumption? That may be a big claim (and I'm not making it!) but I'm sure soy's widespread occurrence in our diet is contributing to our exploding allergy rates.

Especially when the science shows a strong link between the two...

A cross-sectional study of 1601 young adults was done in Australia. The study looked at food and nutrient intakes and asthma risk in young adults. The findings?

Whole milk protected against asthma risk. Soy beverages (soy milk) increased the risk of asthma (23).

A 2 year study tracking the health of 14,000 babies found that those babies who consumed soy based formula were much more likely to develop peanut allergies (a quarter of all the soy drinking babies went on to develop peanut allergies) (24). 


12. Excessive Soy Consumption May Promote Cancer

Now for the big one - soy consumption and cancer.

Soy consumption has been claimed as an 'anti-cancer' food. In fact, researcher M. Messina - in his book 'The Simple Soybean and Your Health' claims that 1 cup of soy products should be consumed every day to prevent cancer.

Though there have been some studies indicating soys anti-cancer properties (25), there have also been many studies showing the opposite to be true.

A 2002 paper linked soy consumption to increased bladder cancer risks (26).

A study published in the Journal of Epidemiology remarked that soy protein intake was significantly correlated with stomach cancer mortality rates in men, and colorectal cancer in a woman (27).

Meanwhile, there have been a number of studies showing that genistein - an isoflavone found in soy - increases cancer risk and tumor growth (28, 29, 30)

13. Soy Processing Involves Extreme Processing - Exposing You To Dangerous Heavy Metals

Last but not least, unless you are consuming soy beans in their natural state (which is still going to expose you to all the anti-nutrients, hormone suppressing compounds and glyphosate) your processed soy is may be contaminated with harmful heavy metals.

Soybeans undergo an 'acid wash'. This process generally occurs in aluminium tanks, and the acid can leech aluminium into the final soy product.

Dr. Mercola explains this process in his article - Got Thyroid Problems? Then Stop Consuming Soy:

Isolated soy protein powder is actually not a naturally produced substance. Production takes place in industrial factories where a slurry of soy beans is first mixed with an alkaline solution to remove fiber, then precipitated and separated using an acid wash and, finally, neutralized in an alkaline solution. Acid washing in aluminium tanks leaches high levels of aluminium into the final product.

The resultant curds are spray- dried at high temperatures to produce a high-protein powder. MSG, a well-known excitotoxin that can cause neurological damage, is frequently added as well.


Say Good-Bye To Soy Forever?

What's the deal then, is this bean really the worst food in the world? And does it mean you cannot every eat it again?

If you look at the data I have presented above, then yes, it very well may be the worst food you can consume. But do you have to avoid it forever? No. 

Let me explain.

The core problem can be split into two parts.

Firstly, the soy beans that we are eating today is not the same soy as we ate a few generations ago. Today we consume genetically engineered soy that's heavily sprayed with pesticides before going through complex, chemical reliant processing.

Secondly, the soy products we consume today are not prepared in traditional methods like it was in the past.

A lot of the dangers from soy can be avoided if you do three things:

  1. Consume only organically grown soy (to avoid glyphosate contamination and GMO issues)
  2. Avoid any heavily processed soy (protein isolates, soy bean oil etc)
  3. And most important of all - make sure the soy you eat has been fermented to reduce all the remaining dangers that soy brings to the body.

The only type of soy that should be consumed (if you are worried about your health) is fermented organic soy.

Examples of this include:

  • Miso - fermented soy, turned into a paste and often drunk as miso soup.
  • Soy sauce - fermented soy beans with salt. Often includes wheat and most brands today add other ingredients and are made using non-traditional methods.
  • Tamari sauce - a wheat free alternative to soy sauce. A byproduct of the production of miso paste.
  • Tempah - fermented soy beans with a firm cake like texture
  • Natto - fermented soy beans rich in vitamin K2 and beneficial bacteria. 


I hope this article and the evidence presented will make you stop and thinking about your soy consumption habits. Please let me know in the comments section if that is the case.

If you weren't a soy milk drinker, or cooking in soybean oil, but you never thought about soy flour, or soy protein, then I also hope this article has informed you of the dangers of this ingredient.

Again, please share your thoughts in the comments section below, and if you know of someone who consumes a lot of soy - thinking they are doing it to be healthy - please share this article with them.

A healthier population helps all of us!


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This blog post was written by Alex Fergus. Alex is a ISSN Sports Nutrition Specialist, Fitness Professional and certified Superhuman Coach who continues to expand his knowledge base and help people across the world with their health and wellness. Alex is recognized as the National Record Holder in Powerlifting and Indoor Rowing and has earned the title of the Australian National Natural Bodybuilding Champion. Having worked as a health coach and personal trainer for over a decade, Alex now researches all things health and wellness and shares his findings on this blog. Learn more about Alex's Credentials HERE.

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