When I was in naturopathic medical school in the early '90's, I was a serious vegan. My wife and I were co-owners of a vegan restaurant and we had a vegan wedding. What that translated into for us is that we were basically mainlining soy. Tofu, tempeh, soy milk, soy protein powder, soy mayonnaise, soy yogurt, tofu "dogs," "Tofurkey," tofu chocolate pie - these were all a part of our standard daily fare. But gradually we began to notice that our diet wasn't really working for us. For me it was a digestive nightmare. But wasn't soy supposed to the best thing we could possibly eat? How could we possibly consider abandoning soy, especially when some of our mentors, very well respected in the world of nutrition, were convinced of soy's "superpowers"?
One very clear memory I have from one of my favorite professors, was the memory of her mentioning the "one food" that she would have with her on a deserted island. What was it? Soy of course. At that time, research was pouring in over the soy isoflavones that may benefit the heart and breasts. It seemed the perfect food for women. What happened thereafter is that word got out, the dietary supplement industry (as well as "big pharma") caught on and before we knew it soy was everywhere and in everything: cereal, protein powders, dietary supplements, dog food, beverages, meatless "burgers," and more.
The perception that soy is the "perfect food" may still be out there, yet it may be time to relinquish that title; hence the need for an update. This is not to instill fear in vegans or vegetarians, it is simply to set the record straight in terms of knowing what we are putting into our bodies. And to be clear, the purpose of this paper is not to put down soy, it is simply to bring forth the most current information available.
In 2012, over 90% of the soybean crop is genetically modified (GM). According to the American Academy of Environmental Medicine (AAEM), "GM foods pose a serious health risk." Their position paper goes on to state that, "there is more than a casual association between GM foods and adverse health effects" [and that] "GM foods pose a serious health risk in the areas of toxicology, allergy and immune function, reproductive health, and metabolic, physiologic and genetic health." This is very important information to take in when we look at the way soy has infiltrated our food supply.
Whether we know it or not, most of us are consuming large amounts of GM soy. Grocery Manufacturers of America has estimated that as much as 80 percent of processed food on US shelves contains GM ingredients. This includes breakfast cereals and other products labeled "natural" or "all natural." It includes the meat, dairy, and egg products where the animals have been raised on soy and/or corn feed (almost always GM crops unless labeled 100% organic or certified non GM feed).
Soy isoflavones are classified as "phytoestrogens." Phytoestrogens are basically plant-derived substances that have estrogen-like characteristics. They can compete with estrogen for binding sites in the body and they are often used in alternative medicine to try and mimic estrogen activity in individuals who are not candidates for traditional estrogen hormone therapy (in the case of stroke, thrombosis or breast cancer history). When you combine this information with the statement released by the AAEM, I can begin to see how GM soy can potentially disrupt our hormones.
Soybeans (and soy foods) are among a group of foods that have been identified as "goitrogenic." This means they contain goitrogens. Goitrogens are substances that obstruct iodine uptake and can thus inhibit the function of the thyroid gland.
Soybeans contain strong enzyme inhibitors that hinder the action of trypsin and other enzymes needed for protein digestion (J AOAC Int. 2005 May-Jun;88(3):967-87). This may result in acute gastric distress, reduced protein digestion and create chronic deficiencies in amino acid uptakes. Animal studies have shown these affects to be even more severe and leading to significant health challenges including pancreatic insufficiency and cancer. Now I understand why my digestion was so off during my vegan years.
Tofu Versus Tempeh - What is the Difference?
First and foremost, whether you like, love or are indifferent about consuming tofu or other soy products, make sure to choose organic or certified non GMO soy foods whenever possible. Choosing organic fermented soy products like tempeh and miso appears to have more health benefits compared to consuming tofu, soymilk or other types of non fermented soy products.
Tempeh's fermentation process and its retention of the whole bean result in a higher content of protein, dietary fiber, and vitamins. Tempeh has a firmer, chewier texture than tofu and a nutty, earthy flavor. Tempeh has origins in Indonesian culture and cuisine. Miso, originating in Japan, is also a fermented product that is traditionally made from soybeans but also can be made from rice and other grains. Soy based miso is made from soybeans fermented with salt and some type of fungus. These fermented soy products are a good source of probiotics, otherwise known as friendly "gut bugs." Fermentation can actually neutralize or decrease the goitrogens present in soybean products.
Tofu originated in China. It is produced by coagulating soy milk and pressing the resulting curds. Coagulation is accomplished by adding either a salt or an acid to the boiling soymilk. Some evidence suggests that tofu and soy milk may be contributing to thyroid dysfunction or hypothyroidism in women in the United States.
Soy protein isolate or soy protein powder is commercially produced in factories where all kinds of additives and toxins may be present.
Several articles and websites sight a finding by toxicologist Dr. Mike Fitzpatrick, who estimated that infants fed soy formula "receive the estrogenic equivalent (based on body weight) of at least 5 birth controls pills per day. By contrast, almost no phyto-estrogens have been detected in dairy-based infant formula or in human milk, even when the mother consumes soy products." (Campaign for Truth in Medicine). These comments do not come without controversy and is often the case, further research is warranted to substantiate this claim.
There are many books and articles that you can find online on both the perils of soy and the wonders of soy. My own recent PUBmed search on Soy Isoflavones returned 1589 Human studies (If I were to add animal and in vitro studies, that number would quadruple) of which 372 were clinical trials, 26 were meta-analysis, 314 were randomized controlled trials, 395 were reviews. Almost all of the results suggest that further research is warranted.
There is evidence that consuming soy may increase bone density in post menopausal women. In terms of cancer prevention, I remain unconvinced that there is any reason to consume high doses of isoflavones or phytoestrogens like soy in the quest to prevent or treat cancer. Overall, a generous consumption of fresh fruits and vegetables has been associated with decreasing your risk of cancer. One meta analysis suggested that consuming soy isoflavones reduced risk of breast cancer incidence in Asian populations, but not in Western populations (Breast Cancer Res Treat. 2011 Jan;125(2):315-23. Epub 2010 Nov 27). Could this have something to do with GM soy? I don't know - the studies simply are not there.
Soy continues to be advertised as "heart-healthy" and used for type 2 diabetes, asthma, osteoporosis and preventing and treating certain cancers including prostate cancer, endometrial cancer, breast cancer, thyroid cancer and lung cancer. It has been promoted as a possible solution for premenstrual syndrome (PMS), menopausal symptoms, muscle soreness, memory enhancement, and breast pain.
Not all evidence is positive. Some studies have shown no significant benefit. Most research is incomplete or simply lacking. Much of the research is funded directly or indirectly by the soy industry.
Consuming large amounts of soy may interfere with certain medications. For example, estrogen, tamoxifen, and birth control pills. Soy may decrease the effectiveness of coumadin. Check with your doctor and/or pharmacist to see if soy interferes with any of your prescription medication.
It is truly up to each individual to do his/her homework and find out where their food comes from. It doesn't matter if you are vegan, vegetarian, fruitarian or omnivore - now more than ever is the time to choose whole foods that have not been genetically modified. Purchase fewer pre-packaged goods, know your sources and educate yourself. Trufoodnow.org offers a free download and a free App - Shoppers guide for avoiding foods made with genetically modified organisms (GMOs). It is my understanding that tofu must be labeled if it is made from genetically modified soybeans.
Know your body. Write down how you feel after eating certain foods. Keep track of any unusual symptoms or digestive challenges so that you can hone in on what works and doesn't work for your unique physiology. Ask questions of your doctor or well-researched nutritionist. Have regular physicals and have annual bloodwork done to monitor your thyroid and other blood indices. Whether or not you choose to eat or drink soybean products is truly a personal choice. Take the information and do what you need to do to support your highest and best.
List of Soy Alternative Protein Sources: