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Soy in the Vegan Diet: A Practical Approach


Soyfoods are popular, particularly among vegans who often rely on them as a main source of dietary protein.  From whole and fermented foods like edamame, tofu, tempeh, and miso to soy-based products like mock meats and cheeses, everyone seems to be eating a little more soy these days.  But as the market for soyfoods grows, so too, does the conflict among health experts who continue to debate the safety of soy.  While researchers and health professionals weigh in on the purported health benefits and risks of consuming soy, many of us are left wondering:  what role should soy play, if any, in our diets?

Soy: Benefit or Risk to Health?

Soy is an important source of complete protein in the vegan diet, readily providing the body with all eight essential amino acids.  Rich in a group of phytochemicals called isoflavones, soyfoods may help reduce the risk of certain cancers (such as breast, prostate, and colon cancers) and heart disease (soy may help lower the “bad” LDL cholesterol and total cholesterol).  Soy may even help some women build stronger bones and reduce the risk of osteoporosis-related hip fractures.  But despite these findings, some health advocates have raised concerns about the safety of soy in the diet.  And as soy becomes more prevalent in our food supply—some industry experts estimate that as much as 60 percent of the processed foods on the market contain soy, often in the forms of isolated soy protein, soy lecithin, and soybean oils—these concerns are worth considering.

Much of the controversy over soy has centered on whether or not soy may actually increase—not decrease—cancer risk, particularly in those with a hormonally-driven cancer such as breast cancer; cause thyroid disease; and contribute to reproductive or fertility problems.  It is important to know human studies appear to support the safety of soyfoods in the diet, and most experts agree that soyfood consumption is not linked to increased cancer risk, thyroid disease, or reproductive issues.  But there are a few points worth considering in this debate.

Because soyfoods contain isoflavones, phytochemicals that appear to exert estrogen-like effects on some tissues of the body, some people fear that soy could cause or make worse hormonally-driven cancers, such as breast cancer.  Fortunately, human studies have found quite the opposite; it appears that the consumption of soy products may help reduce the risk and recurrence of breast cancer, among other cancers.  Experts do note that the protective effects are seen from food, not supplements, and that more research is needed to learn how the consumption of high amounts of soy might impact cancer recurrence.  But for now, organizations like the American Institute for Cancer Research (AICR) state that women, including those with breast cancer, can safely include up to two or three servings of soyfoods in their diets each day.  However, they also recommend avoiding soy supplements and minimizing soyfoods while receiving anti-estrogen treatments.

While consuming soyfoods appears to have a protective effect when it comes to cancer, some experts have pointed out that highly concentrated proteins—including those from soy—may elevate blood levels of insulin-like growth factor, a compound that has been linked to increased cancer risk.  So while you enjoy soyfoods in your diet, it may be sensible to limit or avoid concentrated sources of soy protein, such as the soy protein isolates that are more commonly found in processed foods.

Finally, when it comes to the health of the thyroid, experts note that soyfoods have not been shown to cause hypothyroidism or any other diseases of the thyroid.  Soy can take up iodine in the body that is intended for the thyroid, and it may decrease the absorption of the medication used to treat hypothyroidism; so if you are being treated for hypothyroidism or are iodine deficient, it is important to discuss your soy intake with your physician, as with any potential drug-nutrient interactions.

Choosing Soy: A Practical Approach

With so much controversy surrounding soy, what is a vegan to do?  I will keep following the experts as they continue their debate over soy.  And in the meantime, here are five tips—a practical approach—for choosing soy in your diet:

1. Choose whole and fermented soyfoods. The protective effects of soyfoods appear to come from consuming soyfoods, not supplements.  Edamame, tempeh, tofu, natto, and soymilk are all good choices.  And if you have concerns over the processing of or ingredients found in your soymilk, choose simple brands like EdenSoy® organic unsweetened soymilk and WestSoy® organic unsweetened soy milk; these brands contain only purified water and organic soybeans.  Of course, you could also choose from other non-dairy milks including rice, coconut, almond, and others.

2. Choose organic. By choosing organic soyfoods, you are ensuring that the soy you consume is not genetically modified and was not grown using pesticides, herbicides, or other chemicals.  As with most other food choices, organic is simply better for your body and environment.

3. Choose processed foods less often, if at all. Soy-based meats, cheeses, ice creams, and other vegan treats can certainly help individuals transition to or easily maintain a vegan diet—and that is great news for many vegans.  But try to build the foundation of your diet from real, whole foods—vegetables, fruits, legumes, nuts, and seeds—and skip or limit the amount of processed foods in your diet.

4. Rethink your protein. Soyfoods provide a simple way for vegans to meet their protein needs.  But remember that you can obtain all of your essential amino acids by simply eating a variety of grains and legumes over the course of each day.  Add to that a few servings of nuts and seeds, and plenty of fresh vegetables—and you will begin to see how easy it is to get the protein you need—with or without soy.

5. Relax. Simply moving toward a vegan diet benefits your health, the animals, and the environment.  Vegans enjoy longer lifespans and reduced risk of chronic disease compared to their animal-eating counterparts.  So no stressing over soy—that will only take years off your life!

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3 comments on “Soy in the Vegan Diet: A Practical Approach”

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Tiffany (NatureMom)
6 Years Ago

I would have to disagree with "experts" that say soy does not cause hypothyroidism. I have avoided soy for years due to its ill effects on health but this past year I started consuming soy daily without knowing it. I failed to read the label on what was marketed as a health food product and was consuming soy for about 2 months when I developed a lump under my breast and my hair started falling out. I was immediately diagnosed with hypothyroidism. The culprit was quite obvious as it was the only change I made and had been perfectly healthy prior to this. After I stopped eating the soy the lump went away within 2 months and my thyroid levels improved. Soy was no health food for me!

Leslie Irvine
6 Years Ago

Most of the misconceptions about the alleged health risks of soy come from the Weston A. Price Foundation, which is dedicated to increasing the consumption of dairy products and meat. Others have done a good job of debunking their quackery, so I won't duplicate it but instead refer interested readers to Leo Babauta's blog: http://zenhabits.net/soy/

Lauri Boone
6 Years Ago

Hi Carolyn, I am not yet on facebook, so I am hoping you check the comments section. Here is the citation you requested: Dewell A, Weidner G, Sumner MD, et al. Relationship of dietary protein and soy isoflavones to serum IGF-1 and IGF binding proteins in the Prostate Cancer Lifestyle Trial. Nutr Cancer. 2007;58(1):35-42. If you have any questions, please don't hesitate to ask! This is certainly a broad topic to fit into a rather brief article. Regards, Lauri


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