The Dark Side of Soy

Is America's favorite health food making us sick?

| Utne Reader July / August 2007



Image by Mo Riza, licensed under Creative Commons.

As someone who is conscious of her health, I spent 13 years cultivating a vegetarian diet. I took time to plan and balance meals that included products such as soy milk, soy yogurt, tofu, and Chick'n patties. I pored over labels looking for words I couldn't pronounce--occasionally one or two would pop up. Soy protein isolate? Great! They've isolated the protein from the soybean to make it more concentrated. Hydrolyzed soy protein? I never successfully rationalized that one, but I wasn't too worried. After all, in 1999 the Food and Drug Administration (FDA) approved labeling I found on nearly every soy product I purchased: 'Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.' Soy ingredients weren't only safe--they were beneficial.

After years of consuming various forms of soy nearly every day, I felt reasonably fit, but somewhere along the line I'd stopped menstruating. I couldn't figure out why my stomach became so upset after I ate edamame or why I was often moody and bloated. It didn't occur to me at the time to question soy, heart protector and miracle food.

When I began studying holistic health and nutrition, I kept running across risks associated with eating soy. Endocrine disruption? Check. Digestive problems? Check. I researched soy's deleterious effects on thyroid, fertility, hormones, sex drive, digestion, and even its potential to contribute to certain cancers. For every study that proved a connection between soy and reduced disease risk another cropped up to challenge the claims. What was going on?

'Studies showing the dark side of soy date back 100 years,' says clinical nutritionist Kaayla Daniel, author of The Whole Soy Story (New Trends, 2005). 'The 1999 FDA-approved health claim pleased big business, despite massive evidence showing risks associated with soy, and against the protest of the FDA's own top scientists. Soy is a $4 billion [U.S.] industry that's taken these health claims to the bank.' Besides promoting heart health, the industry says, soy can alleviate symptoms associated with menopause, reduce the risk of certain cancers, and lower levels of LDL, the 'bad' cholesterol.

Epidemiological studies have shown that Asians, particularly in Japan and China, have a lower incidence of breast and prostate cancer than people in the United States, and many of these studies credit a traditional diet that includes soy. But Asian diets include small amounts--about nine grams a day--of primarily fermented soy products, such as miso, natto, and tempeh, and some tofu. Fermenting soy creates health-promoting probiotics, the good bacteria our bodies need to maintain digestive and overall wellness. By contrast, in the United States, processed soy food snacks or shakes can contain over 20 grams of nonfermented soy protein in one serving.

'There is important information on the cancer-protective values of soy,' says clinical nutritionist Ed Bauman, head of Bauman Clinic in Sebastopol, California, and director of Bauman College. Bauman cautions against painting the bean with a broad brush. 'As with any food, it can have benefits in one system and detriments in another. [An individual who is sensitive to it] may have an adverse response to soy. And not all soy is alike,' he adds, referring to processing methods and quality.

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2/4/2014 11:34:24 AM

I can only speak from my personal experience, I have always love tofu, soy milk and soy products but made sure it was moderate and not overloading myself with soy. After getting married, my husband is great fan of soy milk and soy products and we started to take lots of lots of soy in our diet.The result is GYNECOMASTIA for my husband and irregular periods for me. Have been to the doctors, had ultrasounds of the breast, thyroid and the reason is because of Soy, which contains large amounts of ISOFLAVONES that mimic estrogen, am not saying soy is bad but I would suggest not eating too much of soy or for that matter anything, the idea is to have a wide variety of different kinds of foods in moderation. It has been a few days that we stopped soy intake, we should wait and see how it goes.

9/23/2013 6:17:47 PM

I developed a soy allergy after a year of mild soy intake. It does happen and I believe it's because of the way we are over processing soy.

9/22/2013 7:22:11 AM

'We fare better when we eat according to our ethnicity. Soy is a viable food, but we need to look at how it's used.' What is this - diet advice for racists? This article is five screens full of junk science, fear mongering, and plainly bizarre advice such as the quote above.

9/18/2013 1:37:29 AM

I have been living in Japan for 25 years, and although I can't comment on the depressing scene in the US with its GM beans and highly processed forms of soy, I can tell you that although Japanese may not eat tofu daily, contrary to claims I have seem on some websites, they do eat it on a regular basis, and the young beans (edamame) are consumed on a regular basis as well(when in season). (I just ate a small tub of tofu with edamame, chopped tomato and cucumber, and dressing for lunch!) So, based on the fact that they have been doing so for hundreds of years and are among the healthiest/longest living people on the planet, I would say either Japanese physiology is completely different (highly unlikely), the anti-soy studies have been poorly done or are biased, or the problem is US made. My feeling is that the last suggestion is the most likely one, possibly in combination with the second.

9/15/2013 12:15:56 PM

i ve been vegetarian 3 years and my diet, even before that, contained a large amount o soy---like a half-gallon of Silk terribly Vanilla each 5-6 days, soy cheese, soy nuggets, soy, soy, soy, boy. 2 things once reading this article: No, soy hasn't crumpled my physical attraction, to mention the smallest amount. And, two, i feel it is the explanation for my fucking beginner moobs despite my long commitment to exercise. so I abandoned soy a month ago; currently it's beans, almond milk and legumes, till somebody comes around and says those things cause your intestine movements to glow within the more

8/4/2012 2:39:50 PM

'Soy is not a food that is native to North America or Europe, and you have issues when you move food from one part of the world to another,' Bauman says. That's NO SENSE! According to that we should stop eating bananas, pinapple, potatos, tomato and corn in Europe!

Jola Zandecki
6/22/2012 2:09:52 PM

Interesting article. Although the anecdotal evidence in this article seems to indicate that many individuals are in fact sensitive to soy products, I am not to convinced of the science behind the author’s claims. For a bit more scientific and balanced view on soy I highly recommend folks check out It “is the first non-commercial, science-based website to provide free daily updates on the latest discoveries in nutrition.” To learn more about soy specifically you can follow this link:

DrCarlos Gonzalez
3/20/2012 12:26:49 PM

There will usually always be critics like Anna520 below (probably works for Soy Silk). If you read all the comments below the majority all report negative experiences with soy.

DrCarlos Gonzalez
3/20/2012 12:20:11 PM

This is probably the best article on Soy I have come across! Great job!

10/18/2011 1:40:09 PM

Thanks for this! I always love different views.

5/10/2011 12:29:20 PM

I'm rather appalled that Utne Reader would publish such obvious junk science. The only two sources referred to by name -- Daniel and Bauman -- don't strike me as reliable authorities. Bauman in particular doesn't seem to stand up to scrutiny once you actually try to find information about the college he directs (it seems more like a platform for marketing snake oil than the website of an institution for higher learning). Vague references to unnamed "studies" fill the gaps, leaving the reader frightened but unable to follow up on the claims. While a lot of the claims here are incredibly scary, the fact is that when you look at high-quality studies in peer-reviewed journals, soy seems to be much more benign than either its proponents or detractors make it out to be. Probably not the magic bullet for menopause symptoms, but it's not going to kill you either. Here are some places to start: Hamilton-Reeves, J.M., et al. (2009). Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis; Hooper, L., et al. (2009). Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis; Messina, M. (2010). Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence.

Bob Due
4/7/2011 4:52:51 AM

There is a big difference in the way soy is processed. Most of the soy in food and supplements is solvent extracted and done with heat. If the soy is water extracted with LOW heat, then it is a totally different product. I have been using a soy protein powder since 1970 that has been handled this way and would not want to be without it.

3/29/2011 9:00:29 PM

I've been vegan three years and my diet, even before that, contained a ton o'soy---like a half-gallon of Silk Very Vanilla every 5-6 days, soy cheese, soy nuggets, soy, soy, soy, boy. Two things after reading this article: No, soy hasn't dented my libido, to say the least. And, two, I think it's the cause of my fucking beginner moobs despite my lifelong commitment to exercise. Thus I abandoned soy a month ago; now it's beans, almond milk and legumes, until someone comes around and says those things cause your bowel movements to glow in the dark.

1/26/2011 11:30:37 AM

"We should eat according to our ethnicity." What exactly does that mean? Only Latinos should eat tacos? Only South Asians should eat curry? Only Black people should eat watermelon?

12/16/2010 8:33:53 AM

I switched to a daily serving of light soy milk with my cereal, instead of dairy milk which had been making me feel bloated and uncomfortable. I've been drinking soy for just over a year and I have not experienced any digestion problems or decrease in testosterone. After reading this, I will probably do the occasional substitution with almond milk for a little more soy moderation, though I'm not crazy about the taste.

10/13/2010 11:32:04 AM

I have done extensive reading on the pro's and con's of soy. Maybe you should and you too will figure out that soy is not good for Humans or animals to consume. Unless it is fermented as the Asians ferment it. But here it America it is not done that way and that is why it is NOT a healthy food to eat. But to all you doubters, go ahead and eat it. No one is telling you not to, they are just saying it's bad to eat. When you are sick everyday with mysterious ailments and end up with cancer one of the foods to not eat on the list your oncologist will hand you will be "Soy". Thank you Mary for taking the time out of your day to post this insightful blog.

10/13/2010 11:27:06 AM

I have done extensive reading on the pro's and con's of soy. Maybe you should and you too will figure out that soy is not good for Humans or animals to consume. Unless it is fermented as the Asians ferment it. But here it America it is not done that way and that is why it is NOT a healthy food to eat. But to all you doubters, go ahead and eat it. No one is telling you not to, they are just saying it's bad to eat. When you are sick everyday with mysterious ailments and end up with cancer one of the foods to not eat on the list your oncologist will hand you will be "Soy". Thank you Mary for taking the time out of your day to post this insightful blog.

8/18/2009 2:27:53 PM

This is not crazy. I diagnosed myself 10 years ago, with this problem when no doctor could figure it out...I'd basically replaced all cow's milk with soy and was drinking some everyday. I was also eating tofu. After several months, I began experiencing horrible headaches, and seemed to have perpetual PMS symptoms- irritability, bloating, sore breasts, pimples. I was 30 years old and had always been healthy. It became almost debilitating. Then, one day, I was at the gym and saw an ad posted in the locker room aimed at menopausal women. It said that soy mimics human estrogen and that these women could ease their symptoms by taking a soy supplement. It immediately became clear to me that I was experiencing soy overload. I went to my doctor and asked her about my theory. She said it was plausible. So, I stopped consuming soy completely and after two weeks, all of my horrible symptoms vanished. I avoid soy now and always tell other women about this. I think the problem in this country is that we always want to overdo everything- even what should supposedly be a good thing- without asking questions. Don't just throw yourself into one mindset or diet- ask questions first and be cautious. You can't trust the FDA. They are understaffed and unable to protect the public health.

8/12/2009 2:07:34 PM

Hi, This is crazy I cant believe what i just read.I have been drinking and eating soymilk and edamane beans. And other soy products for years.

Katherine Heicksen
8/17/2008 6:40:29 PM

I would love to see some sources on this one, and on any articles of this type. Its always nice to be able to review the info one's self. Could you post sources?