Are Soy Foods Safe?

Let me start off by saying that I was a fan of soy foods for a few years. For those of us with chemistry not especially-well designed to digest fats, soy seemed like a great idea---that is, until now. I am sure many of you are going to be disappointed by this post because you are happy with your soy milk, soy shake, soy protein bars, soy cheese, soy crumbles, soy cereal, and the beloved soy ice cream! I am going to present some facts here and you can decide for yourself whether you want to continue eating soy foods.


The early promotion of soy products in the U.S. was aimed primarily at vegetarians, anxious for a meat substitute, and the poor. Today this has changed dramatically as marketing of these products is directed towards the "health-conscious" consumer. The fact of the matter is, soy is big business in the U.S. This has been particularly true since 1998 when an FDA ruling permitted a health claim for soy based on research that under certain conditions it could lower cholesterol. Unfortunately, today we have an overwhelming body of published, reliable research which demonstrates that most soy foods are detrimental to your health. Further research is underway as concerns mount.


Fact: Soy protein is extremely difficult to digest due to its high content of naturally-occurring antinutrients including trypsin inhibitors, lectins, saponins and phytates.


Many people suffer from intestinal gas when eating soy foods. This may be due to the trypsin inhibitors which actually inhibit your protein digestion. Keep in mind that cooking will not eliminate soy trypsin inhibitors entirely. It may surprise you to learn that soy is actually high on the list of human potential allergens. Therefore, another likely explanation is that many individuals may be suffering from an undiagnosed soy allergy or sensitivity.


Some in the soy industry claim trypsin inhibitors don't pose a digestive problem. I would seriously disagree. Let's look at how this works. When you eat soy foods, trypsin inhibitor in the food signals the hormone CCK (cholecystokinin) to get the pancreas to secrete more digestive enzymes. If this happens infrequently, it does not tax the pancreas significantly. However, if it happens often, like in the case of those who eat soy foods mostly each day, the pancreas is quickly stressed and overburdened. Furthermore, this can lead to enlargement of pancreatic cells and an increase in the number of cells. Since soy is used extensively in the processing of foods in the U.S., it is difficult to totally avoid unless you eat a very clean, whole foods diet.


Phytates are also naturally-occurring compounds found primarily in beans, grains, and seeds. They have a purpose in nature in that they prevent premature germination and are the storage facility for phosphorus which the plant needs to grow. These phytates bind to certain minerals like zinc, calcium, magnesium and iron. This is why I highly recommend that you soak beans and most grains for several hours before cooking to remove most of the phytates. Soy contains enormous amounts of these phytates and therefore requires soaking and fermentation to remove these phytates. Phytates are pretty much intact in soy milk and its products, tofu, TVP, and soy protein isolate. Miso, tempeh, natto, and fermented soy sauce are healthy choices because they go through a process of soaking and fermentation. Phytate in the supplement form, IP6, has shown potential benefit, but it specifically must be taken between meals and other supplements to avoid binding of important minerals.


Lectins and saponins work together to create havoc in the digestive system. When eaten separately, studies demonstrate they are relatively harmless (though research is mounting that many people are lectin-sensitive), but together, as they occur in soy, they have been shown to cause serious sensitivity reactions in the small intestine. It is true that a healthy body can certainly handle a myriad of disturbances from things like lectins, saponins, and phytates, but even the strongest constitution can be affected if constantly assaulted.


Soy contains substantial amounts of manganese which is a trace mineral we need for things like growth, wound-healing, and brain function. The problem is soy contains high amounts of manganese. Some studies have linked manganese toxicity to learning disabilities, ADD, and behavioral disorders. This was revealed at a September 2000 Conference of Nutritionists, Pediatricians, and Toxicologists at the University of California at Irvine. Infants on soy formula take in approximately 75-80 times more manganese than those who are breast fed or dairy formula fed (http://72.167.254.180/2006/Daniel%20Kaayla%20MV%20article.pdf).


Fact: Soy foods contain goitrogens. These are substances that block the synthesis of thyroid hormones.


Foods like broccoli and cabbage also contain goitrogens, however, they are rarely eaten excessively and they are neutralized by cooking or fermentation. Soy foods are resistant to these methods.


The phytoestrogens in soy, primarily genistein and daidzein, have been shown to inhibit thyroid peroxidase which is involved in T3 and T4 synthesis. Interference with T3 and T4 production can lead to decreased levels of thyroid hormones. So if you are trying to increase your metabolism to lose some weight, you definitely don't want to consume soy foods. There are concerns about the estrogen effects of soy, and the results of research are inconsistent. Breast cancer patients are usually advised by their physicians to avoid soy products.


There was an alarming announcement in 1999 at the Third International Symposium on the Role of Soy in the Prevention and Treatment of Chronic Disease in Washington DC. Research showed that 2 or more servings of tofu per week in midlife would likely lead to cognitive decline, senile dementia, and brain atrophy later in life. This was based on the research of Lon R. White, MD a neuro-epidemiologist at the Pacific Health Institute in Honolulu (http://archives.starbulletin.com/1999/11/19/news/story4.html


If you are not allergic to dairy or suffer from lactose intolerance, I highly recommend you reintroduce dairy products into your diet rather than eat soy. Purchase organic, grass-fed products or locally-produced, hormone-free, grass-fed products.


There is some good news. The traditional oriental soy foods, miso, tempeh, natto, and naturally-fermented soy sauce (shoyu), are highly digestible. So if you enjoy these foods, I do recommend their moderate consumption for those not allergic to soy. Edamame, because it is the young soy bean, appears relatively safe if eaten in small amounts as they do in the oriental countries (not a bowl full). Again, keep in mind it would not be a good choice if you tend to overeat Edamame (more than a few pieces) and you are trying to increase your metabolic rate.


If you want to learn more details about the research on soy, I highly recommend The Whole Soy Story written by Kaayla T. Daniel, PhD, CCN.