Vegans and Vegetarians: Let's Talk About Soy

Do You Eat Soy?

So, what’s all the rage about soy? After all, it’s a bean, a quite controversial bean and a matter of much current debate. There are two strong and opposing views about soy consumption. The research varies greatly concerning whole soybeans and processed soy products such as soy protein isolate and soybean oil. Much of the controversy surrounds the bioactive components such as saponins, phytic acid, protease inhibitors, oxalates, goitrogens, and the phytonutrient, genistein, which is an estrogen-like isoflavone. The soybean is a complete protein source supplying all 8 essential amino acids which makes it valuable for individuals following a plant based diet. It’s also a cheap crop that grows easily in the U.S. Finding a cheap protein source seems like a win, win. Consuming small quantities of whole, organic, cooked soybeans and fermented varieties seems to be a healthy addition for most individuals, but the overconsumption of soy, especial soy foods that have been highly processed and are genetically modified, can have detrimental health effects. Many publications have made significant claims concerning soy and hence, the debate: Is soy safe to eat or not?

What is Soy?

Soybeans, or soya beans, are seeds from the plant, Glycine max. They have been cultivated in East Asia since the 11th century B.C. according to the website, www.ncsoy.org. Originally, soybeans were grown and used for fertilizer due to the nitrogen fixing ability of its roots and prized in crop rotation practices. Raw soybeans are toxic to humans, chicken, pigs and all mono-gastric animals and must be cooked in wet heat to destroy the trypsin inhibitors (Circle et al., 1972). A slow fermenting process was developed to reduce the anti-nutrient affect of some of its constituents and to aid in digestibility (Daniels, 2005). Soon after, soy consumption became a regular practice in much of Asia. The website, www.soyfoods.org, says that soybeans came to America in 1765 by a sailor named Samuel Bowen who had visited China. Soy was only used for industrial purposes prior to the 1920s. The U.S. has become the largest producer of soybeans in the world with 85% of the soybean crops processed into oil and animal feed. Soybean oil replaced tropical oils that were found in many foods because it was cheaper (Mercola, 2010). Genetic engineering of this crop began in 1998. As of 2010, 93% of soybeans grown in the US are genetically modified (NASB, 2010). Traditional soy foods include fermented soybeans such as tempeh, miso, natto and soy sauce and also tofu, made from whole, pureed, cooked soybeans and have been enjoyed in Asia for centuries. ‘Modern day’ soy foods include soybean oil, extracted using hexane or other solvents, leaving behind defatted soy flour. This soy flour can be mixed with proteins to make animal feed or washed with water to create soy protein concentrate. Soy protein concentrate is used to create even more highly processed soy foods such as TVP (textured soy protein) and SPI (soy protein isolate) through an extrusion process. Many low-fat soy milks use SPI. Many meat substitutes use TVP. These highly processed variations of soybeans are vastly different from its whole food form. In America, soy is more often used as a meat and dairy substitute as opposed to a legume that we incorporate into a healthy, whole foods diet. Highly processed variations of soy do not contribute to our health. Fermented variations, such as miso, tempeh and natto, seem to be the healthiest ways to incorporate soy into your diet.

The nutritional properties of soy seem impressive. Soy is praised as a valuable source of protein and fiber, with no cholesterol and very little saturated fat. This information may be the reason that the Food and Drug Administration authorized a health claim linking soy consumption with lowered risk of coronary heart disease in 1999 (Daniels, 2005). Depending on the variation of soy that you consume, it can be high in iron, phosphorus, omega 3 fatty acids, magnesium, potassium, molybdenum, and manganese. There are also unique proteins, peptides and phytonutrients in soy. The way that your body utilizes these nutritional properties seems to spur the debate.

The Controversy

The interest in the health benefits of soy consumption is understandable. Observing populations that consume soy on a regular basis, such as the inhabitants of eastern Asia, which have lower incidences of bone fractures, cardiovascular disease, age related brain problems, menopausal symptoms and breast and prostate cancers, make us hopeful that soy could be the answer (Barrett, 2006). Approximately 2,000 soy-related papers are published every year (Messina & Messina, 2010). Both sides of the soy controversy seem to agree that moderate consumption of whole, organic soybeans, either fresh or dried, and fermented variations such as natto, miso and tempeh, are safe and beneficial to eat, allergies aside. The controversy is not focused on the nutrient content but on the beneficial health claims made about soy. The research varies with regards to whole soybeans and isolated soybean derivatives. Epidemiological studies and clinical trials suggest that optimal soy intake associated with health benefits should be between two and four servings per day (Messina & Messina, 2010). Since soy has been advertised as a health food, many people eat or drink it without understanding the consequences of overconsumption. Many people are unaware of the adverse health affects of soy foods that have been processed such as soy milk, soybean oil, soy flour and meat substitute products, and herein lies the problem with soy. The controversy swirls around how much soy consumption is beneficial and when does it become harmful? Soy has many components that can be problematic to our overall health. First of all, soy in high quality form is hard to find. More than 90% of soy grown in the United States is genetically modified which comes with it’s own set of health concerns, including fertility issues (Mercola, 2010). While soybeans are valued as being a complete protein source, the amino acids are not in the right ratios. For instance, soy is low in the essential sulphur containing amino acid, methionine. So a person who relies on soy as a meat and dairy substitute may be deficient in this essential amino acid. Soybeans contain several bioactive components such as saponins, goitrogens, phytic acid, protease inhibitors, oxalates, and isoflavones. Most people can deal with these components in moderation but when eaten in excess can lead to health problems. Soy also contains a substance called hemaggluttin that causes red blood cells to clump together which inhibits the blood from distributing and absorbing oxygen to the body’s tissues. Many of the processed varieties of soy foods have soy protein and isolated soy protein powder in them. These substances are highly processed involving acid washing in aluminum tanks which leaches into the soy product. These soy products are found in protein bars and protein drinks and usually contain MSG, a known excitotoxin that can cause neurological damage, to help it taste better. Soybean oil has replaced healthy tropical oils such as coconut and palm oil in many prepackaged foods because it is cheaper. Soybean oil is chemically treated with hexane or other solvents to extract the oil from the bean and is high in Omega 6, which is unstable and susceptible to oxidative damage. Soybean oil is hydrogenated which produces trans fats and should be avoided. It’s no mystery why processed soy would be damaging to our health but let’s take a deeper look into the bioactive components of the soybean itself. Soybeans contain several bioactive components such as saponins, goitrogens, phytic acid, protease inhibitors, oxalates, and isoflavones. Dr. Kaayla Daniels says, “ Saponins injure the gut mucosa and contribute to ‘leaky gut syndrome’. Cooking does not remove saponins. The process of fermentation does reduce the saponin content. Saponins can also lower cholesterol (Daniels, 2005). Goitrogens are substances that block the synthesis of thyroid hormones. They can also interfere with iodine metabolism which affects thyroid function. Phytates (phytic acid) binds to minerals such as calcium, iron, zinc and magnesium preventing the body from absorbing them which can lead to mineral deficiencies. Soybeans have one of the highest phytate levels of grains and legumes. Protease inhibitors interfere with protein digestion. Long fermenting processes, such as with miso, can reduce the effects from the protease inhibitors and phytic acid. Oxalates can be a problem if eaten in excess because they can become concentrated in the body fluids and crystallize. Oxalates can also interfere with calcium absorption. Isoflavones are phytoestrogens which have plant based, estrogen-like structures which can affect reproduction and decrease testosterone levels. Genistein, the isoflavone in soy has been studied extensively. A study published in the October 2005 issue of Biology of Reproduction, linked genistein with effects such as altered ovarian function, infertility, and abnormal estrous cycle in mice (Jefferson, 2005). Isoflavones can also disturb endocrine function which can lead to infertility (Mercola, 2010). It has also been known to alter a woman’s menstrual cycle. It is believed that monks consumed soy to aid them in their sexual abstinence because it decreases testosterone levels (Daniels, 2005). It is important to note that these bioactive compounds are not unique to soy and are found in other foods as well. The problem and concern with soy is the overconsumption of this food and its many processed derivatives. It has been promoted as a healthy meat and dairy substitute which may mean that people are eating too much of it with the belief that they are making healthy choices. There are also other individual considerations when choosing to add soy to your diet. The U.S. Centers for Disease Control state that soybeans are one of the top eight foods associated with food allergies. If you notice common symptoms of food allergy or sensitivity such as runny nose, itchy eyes, skin rashes, or gastrointestinal disturbances when you eat soy, you may want to avoid it. Another consideration is that there are several studies showing that soy consumption has adverse affects on thyroid health including thyroid suppression and goiter formation (Doerge & Sheehan, 2002). If you have thyroid issues or a family history of thyroid issues such as hypothyroidism, you may want to avoid soy consumption. If you are pregnant, or trying to get pregnant, you may want to avoid soy. In 1992, The Bulletin de L’ Office Federal de la Sante Publique presented findings that 100 grams of soy protein contains the estrogen equivalent to the contraceptive pill. One study showed that developing females in utero exposed to genistein, the isoflavone in soy, caused harm to their reproductive systems (Jefferson, et al., 2009). Other studies links the excess consumption of phytoestrogens, such as those found in soy, to infertility and abnormal fetal development (Konkel, 2009). If you are at high risk of developing breast cancer, or currently have breast cancer, you may want to avoid eating high amount of processed soy foods. The website www.breastcancer.org, last modified on May 8th, 2013, states, “Until the issue becomes clearer, many doctors recommend that women who take hormonal therapy or who have estrogen-receptor-positive breast cancer avoid soy supplements because they contain high concentrations of isoflavones.”, but this is debatable. Isoflavones in preclinical studies have been shown to promote estrogen dependent breast cancer growth (Cohen, 2010). If you are male, you may want to limit your soy consumption. Many active men are unaware of how much soy are in sources such as protein bars and protein drinks. Research shows that men who were fed 56 grams of pure soy per day for 28 days experienced a 19% drop in serum testosterone (Goodin, et al., 2007). Men who consume considerable amounts of soy had lower sperm concentration which can affect reproduction (Chavarro, et al., 2008). Soy consumption may increase the risk of developing prostate cancer in men (Ward, et al., 2010) but there is also opposing resesrch. Individuals with existing kidney or gallbladder problems may want to avoid eating soy due to the presence of oxalates in the soybeans. Oxalates can become too concentrated in the body and crystallize. They can also interfere with calcium absorption, so people with osteoporosis may want to be careful. If you choose to include soy in your diet make sure it pertains to your own biochemical needs and don’t overdo it. On the flip side of the controversy, soy offers many health claims. Some suggest that the ‘soybean can do it all’. These include reducing the risk of coronary heart disease, helping fight osteoporosis, protection against breast cancer, prostate cancer and colon cancer and offering bone health benefits according to the website, www.ncsoy.com. That’s why there have been so many studies done to disprove these claims as previously discussed. Many that advocate for soy in place of meat and dairy consumption argue the health benefits of soy. Soy is higher in folate and Vitamin K, has more calcium, magnesium and iron, and has more fiber than meat. Soy also has no cholesterol and very little saturated fat. Even though soy is a plant protein and may contain smaller amounts of protein building amino acids than dairy and meat, soy contains unique peptides. These peptides have been shown to help our bodies with improved immune function, improved blood pressure regulation and better blood sugar level control as stated on the website, www.soyfoods.org. Some studies have shown that soy can play a beneficial role in cardiovascular health such as those relating to cholesterol (Zhan & Ho, 2005). According to George Mateljan’s website www.whfoods.com , the isoflavone, genistein, in soy, has been linked to increased activity of antioxidant enzymes and is often the focus in cancer studies. Genistein, can increase the activity of p53, a tumor suppressor protein and can also block protein kinases activity that can slow tumor formation, especially in breast and prostate cancer. The website also notes that genistein becomes more concentrated in fermented soy foods. Greater consumption of foods containing isoflavones, including soy, have been found to reduce the risk of endometrial cancer in postmenopausal women (Ollberding, et al., 2011). A large, population based, prospective cohort study showed strong evidence of soy intake during adolescence and adulthood to have a protective effect against premenopausal breast cancer (Lee, et al., 2009). New studies have suggested that there is a decrease in recurrence for breast cancer survivors who consume soy (Cohen, 2010). Soybeans are also a valuable source of many minerals including copper, magnesium, molybdenum, phosphorus, and potassium. Soy is a good source of the omega 3 fatty acid in the form of alpha linolenic acid (Mateljan, 2007). Claims have been made that soy contributes to bone health but the findings have mixed results. Soy has been shown to improve bone health when the body is able to convert the soy isoflavone, dadzein, into the metabolite, equol. People of Asian decent seem to be able to make this conversion better than Americans (Mariko, 2013). With these health claims, much is still to be investigated. It seems reasonable that most individuals would positively benefit from including small amounts of whole, organic, minimally processed soy and fermented soy foods to their diet. Soy consumption remains a controversial health issue. There is still much to be investigated. It is important to understand the associated health concerns and to fully educate yourself on foods that you choose to incorporate into your diet. Your body has its own specific biochemical needs. Keep in mind that soy is a legume and may have a place as part of a whole foods diet, eaten in moderation. My personal position on the soy controversy is as follows: I think enough research exists to error on the side of caution when tempted to use soy as a meat and dairy replacement. I believe that the overconsumption of soy foods, especially processed varieties, is very risky. As with food choices in general, I believe it is wise to eat a variety of whole foods, including legumes such as soybeans, to promote optimum health. I also support eating fermented varieties of whole foods including soybeans. Even Dr. Kaayla Daniels, author of The Whole Soy Story, admits to eating miso soup on occasion. Dr. Mercola, a popular advocate of current natural health information, also agrees that fermented soy has health benefits. Eat a variety of whole, organic and fresh foods that are minimally processed. Don’t rely on any one food source for all of your protein needs. Any food eaten in excess is probably not good for you.


References

Barrett, Julia R. (2006). The Science of Soy: What Do We Really Know? Environmental Health Perspectives June; 114(6): A352-A358. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1480510/

Bulletin de L'Office Federal de la Santé Publique, No 28, July 20. (1992).

Chavarro, JE, Toth, TL, Sadio, SM, & Hauser, R. (2008). Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Human Reproduction 2008, Vol. 23. No. 10, 2584-2590. http://www.ncbi.nlm.nih.gov/pubmed/18650557

Circle, Sidney Joseph & Smith, Allan H. (1972). Soybeans: Chemistry and Technology. Westport, CT: Avi Publishing. pp. 104, 163. ISBN 0-87055-111-6.

Cohen, Lorenzo PhD. & Lee, Richard M.D. (2010). The Soy - Breast Cancer Controversy. http://www2.mdanderson.org/cancerwise/2010/03/soy-breast-cancer-controversy.html

Daniels, Kaayla T. (2005). The Whole Soy Story: The Dark Side of America’s Health Food, New Trends Publishing, Inc. Washington DC Doerge, Daniel R. & Sheehan, Daniel M. (2002). Goitrogenic and Estrogenic Activity of Soy Isoflavones. USA Environmental Health Perspective. 2002 June; 110(Suppl 3): 349–353.

Goodin, S, Shen F, Shih, WJ, Dave N, Kane MP, Medina P, Lambert GH, Aisner J, Gallo M, & DiPaola RS. (2007). Clinical and biological activity of soy protein powder supplementation in healthy male volunteers. Cancer Epidemiol Biomarkers Prev 2007;16:829–833. Jefferson, Wendy. (2005). Adverse Effects on Female Development and Reproduction in CD-1 Mice Following Neonatal Exposure to the Phytoestrogen Genistein at Environmentally Relevant Doses. Biology of Reproduction October Issue. Vol. 73 no.4 p. 798-806. http://www.biolreprod.org/content/73/4/798.short?related-urls=yes&legid=biolreprod;73/4/798

Jefferson, Wendy N, Doerge, Daniel, & Newbold, Retha. (2009). Oral exposure to genistin, the glycosylated form of genistein, during neonatal life adversely affects the female reproductive system. Environmental Health Perspective 2009 Dec;117(12):1883-1889.

Konkel, Lindsey. (2009). Soy Foods: Eating too much of a good thing might be bad, scientists say. Environmental Health News. Nov. 3, 2009. http://www.environmentalhealthnews.org/ehs/news/estrogenic-effects-of-soy

Lee, SA, Shu XO, Li H, Yang G, Cai H, Wen W, Ji BT, Gao J, Gao YT, Zheng W. (2009). Adolescent and adult soy food intake and breast cancer risk: results from the Shanghai Women's Health Study. Am J Clin Nutr. 2009. JUne 2009 vol 89 no. 6 p. 1920-1926. http://ajcn.nutrition.org/content/89/6/1920.abstract

Mariko, Uehara. (2013). Isoflavone metabolism and bone-sparing effects of daidzein-metabolites. Department of Nutritional Science, Faculty of Applied Bioscience, Tokyo University of Agriculture, Journal of Clinical Biochemistry and Nutrition Vol. 52 (2013) No. 3 p. 193-201 Mateljan, George. Tofu and Tempeh. http://www.whfoods.com/genpage.php?tname=foodspice&dbid=150

Mercola, Dr. Joseph. (2010). Got Thyroid Problems? Then Stop Consuming This “Healthy” Food October 13, 2010. http://articles.mercola.com/sites/articles/archive/2010/10/13/soy-controversy-and-health-effects.aspx Messina, Mark & Messina, Virginia. (2010). The Role of Soy in Vegetarian Diets. Nutrients. 2010 August; 2(8): 855-888. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257705/

National Agricultural Statistics Board annual report (NASB). (2010). June 30, 2010. Retrieved July 23, 2010. North Carolina Soybean Producers Association, Inc. http://www.ncsoy.org/ABOUT-SOYBEANS/History-of-Soybeans.aspx

Ollberding, NJ, Lim U, Wilkens LR, Setiawan VW, Shvetsov YB, Henderson BE, Kolonel LN, Goodman MT. (2011). Legume, soy, tofu, and isoflavone intake and endometrial cancer risk in postmenopausal women in the multiethnic cohort study. Journal of Natl Cancer Inst. 2011.doi: 10.1093/jnci/djr475. http://jnci.oxfordjournals.org/content/early/2011/12/11/jnci.djr475

Soy Food FAQs. http://www.soyfoods.org/soy-information/faq

Soy Nutritional Content. http://www.soyconnection.com/soy_foods/nutritional_composition.php

U.S. Center for Disease Control (CDC). http://www.cdc.gov/healthyyouth/foodallergies/

U.S. Food and Drug Administration (FDA). (2013). Title 21, Volumn 2, Revised as of April 1, 2013 http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.82

Ward, Heather A, Kuhnle, Gunter GC, Mulligan, Angela A, Lentjes, Marlene AH, Luben, Robert & Khaw, Kay- Tee. (2010). Breast, colorectal, and prostate cancer risk in the European Prospective Investigation into Cancer and Nutrition-Norfolk in relation to phytoestrogen intake derived from an improved database. American Journal of Clinical Nutrition 2010 Feb;91(2):440-8. http://ajcn.nutrition.org/content/91/2/440.abstract?sid=91353595-73af-4f21-b034-ad259835c6eb.

Zahn, Siyan & Ho, Suzanne C. (2005). Meta-analysis of the Effects os Soy Protein Containing Isoflavones on the Lipid Profile. The American Journal of Clinical Nutrition. February 2005 Vol 81 no. 2 p. 397-408

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