Dangers of Soy

Some people have publicly said that soy is a beneficial food and we should eat more of it, especially as a replacement for red meat. Many vegetarians rely heavily on it for their protein. It has been claimed to be good for women who are menopausal or peri-menopausal. But how true is this? Let’s take a look at some of the myths about soy, and the real truth. Thanks to the Weston A Price Foundation for the following information:

Myth: Use of soy as a food dates back many thousands of years.
Truth: Soy was first used as a food during the late Chou dynasty (1134-246 BC), only after the Chinese learned to ferment soy beans to make foods like tempeh, natto and tamari.

Myth: Asians consume large amounts of soy foods.
Truth: Average consumption of soy foods in Japan and China is 10 grams (about 2 teaspoons) per day. Asians consume soy foods in small amounts as a condiment, and not as a replacement for animal foods.

Myth: Modern soy foods confer the same health benefits as traditionally fermented soy foods.
Truth: Most modern soy foods are not fermented to neutralize toxins in soybeans, and are processed in a way that denatures proteins and increases levels of carcinogens.

Myth: Soy foods provide complete protein.
Truth: Like all legumes, soy beans are deficient in sulfur-containing amino acids methionine and cystine. In addition, modern processing denatures fragile lysine.

Myth: Fermented soy foods can provide vitamin B12 in vegetarian diets.
Truth: The compound that resembles vitamin B12 in soy cannot be used by the human body; in fact, soy foods cause the body to require more B12

Myth: Soy formula is safe for infants.
Truth: Soy foods contain trypsin inhibitors that inhibit protein digestion and affect pancreatic function. In test animals, diets high in trypsin inhibitors led to stunted growth and pancreatic disorders. Soy foods increase the body’s requirement for vitamin D, needed for strong bones and normal growth. Phytic acid in soy foods results in reduced bioavailabilty of iron and zinc which are required for the health and development of the brain and nervous system. Soy also lacks cholesterol, likewise essential for the development of the brain and nervous system. Megadoses of phytoestrogens in soy formula have been implicated in the current trend toward increasingly premature sexual development in girls and delayed or retarded sexual development in boys.

Myth: Soy foods can prevent osteoporosis.
Truth: Soy foods can cause deficiencies in calcium and vitamin D, both needed for healthy bones. Calcium from bone broths and vitamin D from seafood, lard and organ meats prevent osteoporosis in Asian countries—not soy foods.

Myth: Modern soy foods protect against many types of cancer.
Truth: A British government report concluded that there is little evidence that soy foods protect against breast cancer or any other forms of cancer. In fact, soy foods may result in an increased risk of cancer.

Myth: Soy foods protect against heart disease.
Truth: In some people, consumption of soy foods will lower cholesterol, but there is no evidence that lowering cholesterol improves one’s risk of having heart disease.

Myth: Soy estrogens (isoflavones) are good for you.
Truth: Soy isoflavones are phyto-endocrine disrupters. At dietary levels, they can prevent ovulation and stimulate the growth of cancer cells. Eating as little as 30 grams (about 4 tablespoons) of soy per day can result in hypothyroidism with symptoms of lethargy, constipation, weight gain and fatigue.

Myth: Soy foods are safe and beneficial for women to use in their postmenopausal years.
Truth: Soy foods can stimulate the growth of estrogen-dependent tumors and cause thyroid problems. Low thyroid function is associated with difficulties in menopause.

Myth: Phytoestrogens in soy foods can enhance mental ability.
Truth: A recent study found that women with the highest levels of estrogen in their blood had the lowest levels of cognitive function; In Japanese Americans tofu consumption in mid-life is associated with the occurrence of Alzheimer’s disease in later life.

Myth: Soy isoflavones and soy protein isolate have GRAS (Generally Recognized as Safe) status.
Truth: Archer Daniels Midland (ADM) recently withdrew its application to the FDA for GRAS status for soy isoflavones following an outpouring of protest from the scientific community. The FDA never approved GRAS status for soy protein isolate because of concern regarding the presence of toxins and carcinogens in processed soy.

Myth: Soy foods are good for your sex life.
Truth: Numerous animal studies show that soy foods cause infertility in animals. Soy consumption enhances hair growth in middle-aged men, indicating lowered testosterone levels. Japanese housewives feed tofu to their husbands frequently when they want to reduce his virility.

Myth: Soy beans are good for the environment.
Truth: Most soy beans grown in the US are genetically engineered to allow farmers to use large amounts of herbicides.

Myth: Soy beans are good for developing nations.
Truth: In third world countries, soybeans replace traditional crops and transfer the value-added of processing from the local population to multinational corporations.

So does this mean we shouldn’t eat soy?

Yes. Unfermented soy products should be avoided. Soy that has been fermented has much of the anti-nutrients neutralised, and can be safely eaten in small amounts. This includes tempeh, miso and tamari.

But like the Asians, think of soy as a condiment – a small part of a balanced diet. Don’t rely on it for your protein.

To summarise the dangers of soy:

  • High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets have caused growth problems in children.
  • Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders. In test animals soy containing trypsin inhibitors caused stunted growth.
  • Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women.
  • Soy phytoestrogens are potent antithyroid agents that cause hypothyroidism and may cause thyroid cancer. In infants, consumption of soy formula has been linked to autoimmune thyroid disease. They also block thyroid medication, so people on those meds shouldn’t have soy at all.
  • Vitamin B12 analogs in soy are not absorbed and actually increase the body’s requirement for B12.
  • Soy foods increase the body’s requirement for vitamin D.
  • Fragile proteins are denatured during high temperature processing to make soy protein isolate and textured vegetable protein.
  • Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines.
  • Free glutamic acid or MSG, a potent neurotoxin, is formed during soy food processing and additional amounts are added to many soy foods.
  • Soy foods contain high levels of aluminum which is toxic to the nervous system and the kidneys.

For more information check out the Soy Alert section of the Weston A Price Foundation

For a personal perspective on the effects of soy, here is a letter that was printed in the Winter, 2002 edition of Wise Traditions, the quarterly magazine of the Weston A Price Foundation.

To this I can add that I know of more than one man who has had a major reduction in sex drive after eating soy regularly. After stopping eating soy, things went back to normal.


Thanks for your website! I found it by doing a Netscape search on isoflavones which took me to soyonlineservice.co.nz which took me to you.

Until 2 years ago I was a regular consumer of homemade soymilk. I have a PhD in plant physiology and over the years I systematically worked to optimize the process I used at home so that I could make a soymilk much more palatable than any on the market. I had an interest in eventually starting a business to make it. But then I learned that I probably had an adverse reaction to isoflavones in the soymilk and 1 stopped consuming soyfoods.

I tried taking isolated soy isoflavones. basically just to see what effect they had and also because they were reported to be good for prostate health (I am 57). (I am aware that there are studies pro and con benefit to prostate.) I took 2 SoyCare tablets (a total of 50 mg Novasoy isoflavones)- A few hours later I found that it was difficult to speak and I nearly got into a serious accident due to impairment in judging the speed of a car. I definitely had serious mental impairment which I attributed to the isoflavone supplement. (This was gone by the next day.) I don’t think it was due to an allergic reaction or mini-stroke.

Once before I had similar difficulty in speech when a doctor gave me an atropine-like medicine, Atropine antagonizes acetylcholine action, which triggers some of the nerves involved in memory. Memory is an essential component of speech!

Previously I had thought (based on ignorance) that isoflavones in soy probably had insignificant health effects. After the reaction to the isoflavones, I starting searching Bioabstracts for studies on soy isoflavones. I quickly learned that genistein is a potent inhibitor of tyrosine kinase, a key enzyme in mediating cell responses to our natural cell growth factors. (It had been used for this purpose in over 1000 research studies!) That did not sound like something I wanted in my food! Furthermore, I found several studies that showed that tyrosine kinase is also involved in triggering of nerves involved in memory, and this is blocked by genistein! My memory was flaky enough already and I quit eating soy products, except for a few subsequent trials of soy milk.

Besides inhibition of lyrosine kinase, adverse cognitive effects of soymilk could also be due to anti-estrogenic actions (estrogens are important for speech and memory in both males and females) or to anti-thyroid action. Or maybe to all three!

All my adult life I have been bothered by rather severe seasonal affective disorder (SAD, winter mental sluggishness) when I lived at northern latitudes. In the last two years I have rarely drunk soymilk, but when I did, it seemed to worsen the SAD and each time I felt an undesirable aggressiveness. (A recent study showed soy isoflavones increased the potent androgen dihydrotestosterone in men.) I think my particular physiology made me more susceptible to soy’s adverse effects. Subsequently I learned of the Hawaiian study on elderly Japanese. It was the first time I heard that soy may cause cognitive problems.

Gene Samuels Reston, VA

Another soy testamonial that has been doing the rounds by email lately. As there is no name on it, it can’t be verified. But it’s a sobering story, very detailed and with a ring of truth. Read it and decide for yourself whether there could be any truth in it.

This is my true story, nothing altered. These are facts, as they relate to my experience, my opinions based on what I have read and felt am relating them to warn other young health-conscious women who are unwittingly harming themselves.

In 1989, I graduated from high school in Texas and couldn’t wait to hit the big college city. One of the changes I wanted to make was to eat healthier.

Once I moved to health-conscious Austin, Texas, I began to fortify my body with the best and healthiest foods I could find. Tofu was the main ingredient in every healthy dish and I bought soya milk almost every day. I used it for everything from cereal to smoothies or just to drink for a quick snack. I bought soya muffins, miso soup with tofu, soyabeans, soyabean sprouts, etc.

All the literature in all the health and fitness magazines said that soya protected you against everything from heart disease to breast cancer. It was the magical isoflavones, the estrogen-like hormones that all worked to help you stay young and healthy . I looked great, I was working out all the time, but my menstrual cycle was off.

At 20, I started taking birth control pills to regulate my menstrual cycle. In addition to this I began to suffer from painful periods, began to get puffy, it was as though I was losing my muscle tone, began to suffer from depression and getting hot flashes. I mistook all this for PMS since my periods were irregular. By the time I was 25, my periods were so bad I couldn’t walk. The birth control pills never made them regular or less painful so I decided to stop taking them. I went on like this for another two years until I realized my pain wasn’t normal.

At 27, my gynecologist found two cysts in my uterus. Both were the size of tennis balls. I went through surgery to have them removed and thank God they were benign. The gynecologist told me to go back on birth control pills. I didn’t.

In 1998, he discovered a lump in my breast. Again, I went through surgery and again it was benign.

In November 2000 my glands swelled up and my gums became inflamed. Thinking I had a tooth infection I went to the dentist who told me that teeth were not the problem. After a dose of antibiotics the swelling still did not go down.

At this point I could feel a tiny nodule on the right side of my neck. I told my mother I had thyroid trouble. She thought I was being silly. No one in the family suffered from thyroid trouble. Going on a hunch I saw a specialist who diagnosed me with Papillary Thyroid Carcinoma. After a series of tests he told me it was cancer. My fiancé and I sat stunned. We were not prepared and I was so scared. We scheduled surgery right away.

The specialist told us that it would only be after the operation that a pathologist would be able to tell us for sure if it was cancer. They found a tumor at my right lobe composed of irregular cells and another smaller tumor growing on the left, so the entire thyroid was removed.

They told me that after undergoing radioactive iodine I would be safe and assured me that I could live a long life.

After treatment I began to search for the cause of all these problems. I never once thought it could be all the soya I had consumed for nearly ten years. After all, soya is healthy.

I came upon a web page that linked thyroid problems to soya intake and the conspiracy of soya marketed as a health food when in fact it is only a toxic by-product of the vegetable oil industry.

This was insane, after all, the health and fitness magazines had said nothing about soya being harmful.

I visited a herbalist who was diagnosed with thyroid cancer in 1985. She informed me that soya was the culprit. She had a hysterectomy due to cysts and other uterine problems. A few months later another acquaintance who had consumed soya came down with thyroid cancer. A girl in England I met through the internet in a thyroid cancer forum had just undergone surgery and she was only 19.

What was going on?

Breast cancer is linked to estrogen. What mimics estrogen in the female body, SOYA!

But I never suspected soya because until now I never once found a single article that stated soya could be dangerous. Women who took soya prior to thyroid problems will continue to take it after if they are not aware of what soya actually does, what it contains and how it reacts in the female body. I think this is the reason that women with thyroid cancer often develop breast cancer later.

My co-worker is big into soya and I see her losing hair and gaining weight despite a walking workout during her break and after work, and apples and oranges for lunch. She just had cysts removed from her uterus too. I warn her to stay off soya. I refer her to websites but evening news on all four networks, women will suffer. Since the thyroidectomy I do not touch soya, haven’t for two years.

Dear readers, please use my story in any way you can. There are so many young girls who are consuming soya because they think they are taking care of themselves, and women taking soya because they want to be healthy. It is so unfair that the information about the dangers of soya isn’t more widely circulated. It is sad. There are many out there who feel this way and it is a terrible blow when you realize you are not as healthy as you thought and that the information that you depended on was wrong.

Here are a couple of official rulings about soy that are rather telling:


The FDA confirmed on October 4, 2005 that the Solae Company has withdrawn its petition for a soy protein and cancer health claim. Had this health claim been approved, it would have doubled the sales of soy protein in the USA, bringing huge profits to the soy industry while putting American men, women and children at risk.

“This represents a major blow to the soy industry,” says Kaayla T. Daniel, PhD, author of The Whole Soy Story: The Dark Side of America’s Favorite Health Food. “The FDA advised Solae on at least one occasion that it had not convincingly established that soy can prevent cancer and that it had failed to counter massive evidence that soy can cause, contribute to or accelerate cancer growth.”

Dr. Daniel joined the Weston Price Foundation to present much of the scientific evidence against soy that led to the FDA’s questions and to Solae’s withdrawal. The Weston A. Price Foundation has been a leader in alerting the public to the fact that soy protein and soy oil in the food supply have been linked to digestive distress, thyroid damage, reproductive problems, infertility, ADD/ADHD, dementia, heart disease and cancer.

Solae first petitioned the FDA for a health claim in February 2004. Food manufacturers put health claims approved by the FDA on labels and packages to increase sales because they encourage consumers to make “healthier” purchases. The FDA had hoped to announce its final decision on October 23, 2005.

Between June 2004 and April 2005, the Weston A. Price Foundation submitted three detailed and heavily referenced documents to the FDA that refuted the claims for soy and cancer made by the Solae Company, a joint venture of Dupont and Bunge. This summer the Foundation drew the FDA’s attention to a July 2005 health advisory issued by the Israeli Health Ministry that warned that soy infant formula should not be given to infants, that children should be fed soy foods no more than once per day to a maximum of three times per week and that adults should exercise caution because of increased risk of breast cancer and adverse effects on fertility.

In addition, the Foundation spearheaded a write-in campaign to the FDA earlier this year that brought in over 1,000 comments by our members requesting the FDA to not approve Solae’s petition. You are all to congratulated for this fine effort.

In its petition to the FDA, Solae contended that a qualified health claim was warranted because of “substantial scientific agreement” among experts that soy protein reduces the risk of breast, prostate and colon cancers. “No such consensus exists,” says Dr. Daniel. “Scientists at the FDA’s own Center for Toxicological Research have warned of soy protein’s carcinogenic potential and of the health dangers of excess soy-food consumption. We showed the FDA that Solae was highly selective in its choice of evidence and biased in its interpretations. We reported on the fact that they had omitted many studies proving soy to be ineffective in preventing cancer, emphasized favorable outcomes in studies with mixed results and excused the results of the few unfavorable studies that they included to give the illusion of balance. Most importantly, we drew the FDA’s attention to the fact that Solae excluded many studies showing that soy protein can cause and accelerate the growth of cancer, particularly breast cancer.”

In addition to the recent soy warning issued by the Israeli Health Ministry, expert scientists with the British Committee on Toxicity, Swiss Federal Health Service and other government agencies have all expressed concern about soy’s potential to disrupt the digestive, immune and neuroendocrine systems of the human body and its role in rising rates of infertility, hypothyroidism and some types of cancer including thyroid and pancreatic cancers.

Soy is also highly allergenic. Most experts now place soy protein among the top eight allergens, and some rate it in the top six or even top four. The Swedish Health Ministry has warned that allergic reactions to soy are increasingly common, ranging from mild to life threatening, and that fatalities have been reported.

“People are finally starting to hear that soy is not a ‘miracle food,'” says Dr. Daniel. “More and more expert scientists are issuing warnings about soy. The FDA made a big mistake in 1999 when it kowtowed to the soy industry and allowed a soy-and-heart-disease health claim. Today’s FDA is under intense scrutiny because of the Vioxx debacle and could not afford to approve an unfounded soy-prevents-cancer health claim. Solae withdrew its petition because it knew that its science was unconvincing and that the FDA had no choice but to turn them down. The bottom line is that soy does not prevent cancer.”

And in Israel:

Israeli manufacturers of soya products were rattled by the recommendation issued by the country’s health ministry that consumption of soya products be limited in young children and avoided, if possible, in infants. After a year’s work, a committee of experts also advised that adults who eat soya products do so in moderation, pending authoritative future studies. Although research showing possible harm;a higher risk of cancer, male infertility, or other problems from soya is based on animal or retrospective human studies, the committee of 13 issued recommendations based on the precautionary principle.

Soya contains phytoestrogens that may have some of the effects of the human hormone if consumed in large quantities. Soya consumption is high in Israel, and use of soya based baby formula is among the world’s highest per capita. Nevertheless, the ministry decided not to prohibit the sale of soya based formula without a doctor’s prescription, which is already required in New Zealand and Australia.

Widespread soya use in Israel is due to a number of reasons, most prominently kosher food practices. Jewish law and tradition forbid the mixing of milk and meat products, dishes, and cutlery, and after eating meat individuals must wait some six hours before ingesting dairy foods. Although this interval is not required of babies, many ultraorthodox mothers observe it anyway, and those who do not breastfeed prefer soya based rather than cow’s milk formulas so bottles are not on the table during meat meals.

The actual need for soya based formula due to allergy to cow’s milk based formula is negligible. Since soya provides cheaper protein than meat, it is widely served in various forms, especially in day care centres that are spared from using separate dishes and cutlery. Soya burgers made from reconstituted flakes and other forms, many of them developed by Israeli companies, as well as tofu and misu, are popular among health conscious people.

“We don’t know the long term effects on health of large amounts, so we are urging moderation,” said Dorit Nitzan Kaluski, director of the health ministry’s food and nutrition service who was a committee member. “We want to be careful. And while it is easy to identify soya products, there is much more soya added to foods such as breads, cakes, cookies, and crackers.”

Paediatricians will monitor the thyroxine concentrations in infants and toddlers who have hypothyroidism who drink soya based formula or soya foods. And women with breast cancer or a high risk of it will be advised to consult their doctors about soya in their diets.

Dr Nitzan Kaluski said that to avoid pressure from soya food firms, the committee did not inform them in advance, but within a day of the report’s release, she received at least one lawyer’s letter and numerous requests for information. She expects lawsuits are on the way.