How Soy Wreaks Havoc on Digestion and the Pancreas

by Kaayla T. Daniel PhD, The Naughty Nutritionist

soy a danger to the digestive systemSo you got the memo that soy is very bad for the hormonal system.

If you think that is the extent of the damage the lowly soybean can wreak on your health, you may be surprised to learn that soybeans are also notoriously hard to digest with GMO soybeans – widely used in processed foods –  the absolute worst.

The culprit is the protease inhibitors found in all soybeans whether organic or GMO. As the name suggests, protease inhibitors suppress some of the key enzymes that help us digest protein.

The best known and most important of the protease inhibitors is trypsin. GMO soybeans have more of them than organic or conventional beans, and to make matters worse, those protease inhibitors are stubbornly resistant to deactivation by cooking or other processing methods.

Soybeans are not the only foods that contain protease inhibitors. All beans contain them, as do grains, nuts, seeds, vegetables of the nightshade family, egg whites, and other foods. However, the protease inhibitors in those foods rarely contribute to health problems because few of those foods are eaten excessively and cooking deactivates most of them.

In contrast, there are more protease inhibitors in soybeans than in any other commonly eaten food. While protease inhibitors are not a problem for people who enjoy the occasional soy dish, the quantities add up quickly when people consume soy daily in the mistaken belief that it is a “healthy” meat and dairy substitute.

For decades, USDA and other researchers put their efforts into finding safe and inexpensive ways to deactivate the protease inhibitors found in soy. Boiling, roasting and modern processing methods help, but cannot destroy all of these troublesome components. The only way to come close is through the old-fashioned fermentation methods used to make miso, tempeh and natto. Modern industrial processing techniques involving heat, pressure and chemical treatments have been reported to kill off as much as 80 to 90 percent, but that’s a promise, not a guarantee.

The numbers of live protease inhibitors remaining in soy products varies from batch to batch, and investigators have found unexpectedly high levels of protease inhibitors present in some soy foods, and startlingly high levels in some soy formulas.

Protease inhibitors are an especially bad problem in GMO soybeans. With more than ninety percent of commercial soybean crops now genetically modified — up from around fifty percent in 2007 — there are very real health risks. Monsanto, of course, claims these beans are substantially equivalent to the conventional soybean, hence safe.

In fact, tests have shown significantly higher concentrations of protease inhibitors in the toasted GMO soybean compared to conventional soybeans. Furthermore, those found in the GMO strain proved stubbornly resistant to deactivation by the heat treatment known as “toasting.”

When the results first came in, Monsanto took the bad news to mean that the GM beans had not been properly cooked and asked for retreatment of the sample. Further heating, however, widened the difference even more. The logical conclusion would be that a substantial difference exists between the GMO and conventional soybeans, and that the GMO soybean is more likely to cause digestive distress and growth problems in humans and animals.

Monsanto, however, concluded that the second toasting was still not enough and toasted twice more until they got the result they wanted, namely that ALL proteins were denatured and inactivated. At this point, most of the soybean’s protein value was also
destroyed, but it gave Monsanto the “proof” it needed to conclude that where protease inhibitors were concerned, GM and normal soybeans were equivalent.

Protease Inhibitors Do a Number on the Pancreas

Why be concerned about protease inhibitors? They are the reason soybeans are notoriously hard to digest, and why soybean consumption stresses the pancreas. Because the protease inhibitors in soy inhibit the protease enzyme we need to digest protein, the pancreas has to work overtime to produce more. If this happens only occasionally, the pancreas quickly recovers. But if soy is consumed day after day, week after week, year after year, there will be no rest for the weary pancreas. The result is an increase of both the number of pancreatic cells (hyperplasia) and the size of those cells (hypertrophy).

The extent of soy-caused pancreatic hypertrophy and hyperplasia varies widely from species to species in the animal kingdom. In some soy-fed animals, the pancreas swells quickly, in others more slowly, and in some not at all. However, all animals — including the human animal — will suffer from the loss of the ability to secrete sufficient enzymes if regularly consuming protease inhibitors. That means digestive distress for nearly everyone and growth problems for the young.

With pancreatic stress and cell proliferation, cancer becomes a distinct possibility. Pancreatic cancer currently ranks as the fourth leading cause of cancer deaths of men and women in the United States, and is predicted to move into second place by 2020. Back in the 1970s and 1980s, researchers studying damage to the pancreas caused by protease inhibitors noted that pancreatic cancer had then moved up to fifth place, and suggested a soybean-protease inhibitor connection. Since then the rise has been even more alarming.

The fact that it has occurred along with increased human consumption of soybeans — and over the past decade GMO soybeans — is probably not coincidental. Association, of course, does not prove cause and effect, but looking at the rise of pancreatic cancer alongside the evidence of so many animal studies is suggestive and sobering.

Irvin Liener, PhD, professor emeritus at the University of Minnesota and the world’s leading expert on anti-nutrients and toxins in plant foods, sums it up well, “Soybean trypsin inhibitors do in fact pose a potential risk to humans when soy protein is incorporated into the diet.”

For a full discussion and references, read Chapter 16: Protease Inhibitors, Tryping on Soy in The Whole Soy Story: The Dark Side of America’s Favorite Health Food by Kaayla T. Daniel, PhD (New Trends, 2005)

About the Author

dr kaayla danielKaayla T. Daniel, PhD, is the author of The Whole Soy Story: The Dark Side of America’s Favorite Health Food endorsed by leading health experts, including Drs Joseph Mercola, Larry Dossey, Kilmer S. McCully, Russell Blaylock and Doris J. Rapp.

Kaayla has been a guest on The Dr.Oz Show, PBS Healing Quest, NPR’s People’s Pharmacy, and many other shows.

Kaayla  is known as The Naughty Nutritionist because of her ability to outrageously and humorously debunk nutritional myths.    You can read her blog at  You can also find her on Facebook.

Photography Credit



More Information

Why Soy Formula (even Organic) is So Dangerous for Babies

170 Scientific Reasons Confirm the Dangers of Soy


Comments (81)

  1. Pingback: Best Protein Powder For Women

  2. I drink a tall vanilla latte with soy milk from Starbuck nearly everyday. The soy milk they use clearly states on the carton “organic.” I hope this isn’t bad for me.

  3. Vivi Sinaga via Facebook February 16, 2014 at 8:48 am

    Just ferment it to make tempeh,, or ferment the soy milk mix with milk kefir let sit overnight ,, then you may consume it,, its very healthy then

  4. Sandra Stone via Facebook February 16, 2014 at 6:41 am

    Andmothers feed soy formula to their newborns. Soy is dangerous just like the flouride we add to public drinking water.

  5. Sue Fowler via Facebook February 16, 2014 at 4:16 am

    Soy has proteins that are extremely hard to digest, so it sits and ferments in the intestine bringing all kinds of problems like overgrowth of yeast, bacteria and toxins… The only form of soy we should ever ingest, and very sparingly, is fermented soy…

  6. Francine Polito Shannon via Facebook February 16, 2014 at 3:01 am

    Soy killed my thyroid. … phyto estrogens. Plus most of the soy in the US is genetically modified.

  7. Raya King via Facebook February 16, 2014 at 2:05 am

    Soy is a problem, GMO or not. Unless it is fermented, it will mess up your hormones, thyroid and pancreas. I’m talking from experience.

  8. Shelle Michaelson via Facebook February 15, 2014 at 10:42 pm

    Makes you wonder about the rise in Diabetes cases and the corrolation to the increase of soy bi-products in nearly everything !?

  9. Pingback: 10 Reasons to Avoid 98% of Soy | Healthy Concepts with a Nutrition Bias

  10. Pingback: The Truth About Soy for a Gluten-Free Diet | Gluten Free Diet Symptoms Recipes Remedies

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  12. Although I wholeheartedly agree that soy is bad (except for the occasional serving of the fermented types), the article has an error. Trypsin isn’t an enzyme inhibitor. It is actually an enzyme made by the pancreas that breaks down protein (a protease). We with a natural bent need to make sure that we are accurate otherwise we can lose credibility in our fight. Please make sure that you do your homework.

  13. It is my understanding that fermented soy… tempeh and natto are not bad. In fact I read on the WP site that it is a good source of Vit K and several other vits. On the other hand…either temph or natto can be made with other beans. But this brings up the question, since soya beans are related to the rest of the bean family….are legumes all a source of these problems….or just soy??????

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  15. we are meat and dairy free..have occasional local eggs…(more debate and debacle!)…we do not eat alot of meat substitutes or soya in any form really…but we do like organic soya milk in our tea and other hot drinks (my 10 yr old child does not usually drink these)..

    please tell me whether we can carry on drinking soya in moderation like this..(ie; in beverages..)..and eat the occasional organic soya based savory or tofu…also cheezly (a cheese substitute..which contains some soya)… my mother recently found she has a slight under active thyroid…she is now taking thyroid support supplement containing iodine..

    are we really putting our health at risk by such small ammounts?…is it damaging my sons growth etc and my mums thyroid health?

    I would be so grateful for answers. Thank you.

  16. Pingback: Jess Ainscough gives good advice Courtesy of MindBodyGreen | DirtyFilthyHealthy

  17. I was very sick as a child and early adult. My first couple of children were also very sick and I have a child w Juvenile Diabetes. Now, we actually use NON GMO Soy and are much healthier. I couldn’t walk at one point and I am now a Natural Health Provider and very healthy with 6 children.. Our daughter with Juv Diabetes now uses non gmo spy protein and uses less insulin than the docs have ever heard of and is very healthy. The issue IS the GMO. Soy saves lives in 3rd world countries where people die of malnourishment. I am glad you stressed the GMO. We provide our clients with non gmo.

  18. Gia Gulino via Facebook May 8, 2013 at 5:37 pm

    I am a recovering vegan/vegetarian. had pancreatitis twice. too many years of eating soy at every meal. cut it out for good over four years ago.

  19. Has any study been done on whether soy (and I mean real soy, not the stuff that is mangled into textured soy protein, or is a product made into something alongside wheat as ingredient) is better absorbed by, say, Chinese people than by Caucasian people? As in the way certain ethnic groups from areas of Europe and Africa have in their own way adapted to the lactose in dairy, while other groups have not? In China, Japan and other places, they may well eat less soy than we think, but they certainly consume more than most people in America (discounting the obviously bad food like textured soy protein). I am just curious.

  20. Just the fact that GM soybeans are sprayed with the toxic roundup pesticide is enough for me to avoid them completely. According to Bye bye IBS, The Natural Irritable Bowel Syndrome Cure, 93 percent of soy is genetically modified. Then there’s the estrogenic problems and, as Dr. Daniel points out, this whole enzyme inhibitor problem!

  21. Wendy Rolfs via Facebook May 8, 2013 at 12:57 pm

    Elise Rolfs another great article for you to read :) Hope it helps with some of the questions you had …love you!

  22. We are soy free in the kitchen, except we raise meat birds and make our own feed using organic non GMO soybeans. Does that transfer to the chicken meat?

    • yes it does. Switch to field peas. Our chickens are 100% soy free, as we know of many that cannot eat poultry that has been fed soy, no matter the kind.

  23. Isn’t the culprit here GMO and unfermented soy beans? It is my understanding that
    soy made in the traditional way…like natto and real fermented soy sauces is a different
    thing all together….even tofu made traditionally is very much different than our westernized crap!!! If my choices for milk were limited…which they are very….I choose coconut milk.
    It has a variety of great things in it.
    For the most part….I believe the Bible as always is spot on…..Moderation in all things.

  24. Theresa Grant via Facebook May 8, 2013 at 11:21 am

    John, I have yet to try raw milk but will be doing that soon! Good for you and what you do!

  25. I avoid soy completely, as I want no part of the poisons. True, it is in most processed foods, but it is much healthier to avoid those as well. Traditionally, soy was only eaten in very small amounts, mainly as a condiment, and only in a traditionally fermented form, often being fermented for a year or more. Most soy products today are not fermented, and most fermented soy products have been fermented by chemicals in a very short time, which is not the way it was done in the past, and is not the same thing.

  26. Well said Theresa! I totally agree with you on this. The soybean craze is somewhat similar to the margarine is better for your health than butter but we found out that it was false too. I always get concern when there are fades that come in and they say they great and end up being bad in the long run. I am a dairy farmer and I drink raw milk and it has kept me healthy.

  27. Tammy Wagner via Facebook May 8, 2013 at 8:04 am

    Organic non genitally modified soy is actually good for you, especially if it is fermented. Some people consume non organic soy and way too much of it, and that can cause a hormonal imbalance, but there has been NO study showing that some organic soy each day does anything but help improve the hormonal balance in the body.

  28. Its probably to make kids more aggressive to increase the school to prison pipeline. I know I’d be one p.o.ed kid if I didn’t get proper protein…I noticed a while back when I used to eat a lot more grains, if I only ate carbs and little else I would be so hungry within an hour or 2, I was a bear to be around.

  29. here in Iowa back in the late 80’s , our governor lifted the ban on a known cancer causing pesticide for soybeans. The stuff was used generously on bean fields all over the state. I vowed then that I would avoid anything will soy. Since then, we have seen cancer numbers in our area skyrocket.

  30. Karen Reinen via Facebook May 8, 2013 at 12:03 am

    GMO soy is what is bad for you…try to get non-GMO(nearly impossible in this country)!

    • Well that just tells use what side Dr. Weil’s plays for. Both Soy and Canola Oil (GMOs) aren’t good.

  31. I’m not so sure about that. I live on soybeans and have no problems. I’m mean these days everything is bad for you in some way or other. Soy burgers and sausage taste so much better than tofu or other alternatives. I’ll stick with soy no animals have to suffer in the process.

  32. When I pulled this up to read the article I got a notice that the name on the security certificate does not match the owner. Should I worry about that? I wanted to read the article because I am a soymilk drinker having trouble with digestion.

  33. Theresa Grant via Facebook May 7, 2013 at 9:34 pm

    It’s sad that something that is hyped as good for you comes crashing down once again. My MOM has been bugging me to try soy sausage and thinks it’s healthy. I keep telling her I am trying to eat whole foods, not processed foods that have unknown ingredients. What’s wrong with REAL sausage?

  34. Rebeca Beldzik via Facebook May 7, 2013 at 9:31 pm

    Is there a way to detox from previous soy consumption? Consumed in the past out of ignorance and happy to have found out the truth..? Does the soy stay in the body after years of drinking it? at least 5 years? non fermented GMO soy :(!!!

  35. Robbin Roshi Rose via Facebook May 7, 2013 at 9:29 pm

    it’s Genetically Modified soy that seems to be the culprit- unfortunately that’s what we get in the US – not much choice but to avoid it altogether. :-/


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