New to a plant-based diet and worried if you should eat soy or not? We get this question a lot from plant-based beginners — and it’s a good one. Soy is often found in plant-based recipes, from tempeh to tofu to Tamari. But there is a lot of confusion as to whether or not eating soy is harmful or healthy, particularly when it comes to breast cancer risk. We’re here to dissect common soy myths and get to the root of the matter to answer the question: should soy be part of your plant-based diet?
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Soy is a type of legume, originated from Asia. Soy is a popular plant-based protein in vegetarian and vegan communities and can be eaten whole or in processed forms. (More on the different ways soy can be eaten in a bit...)
Worried soy will lead to a breast cancer diagnosis? This is a common plant-based diet myth. It was once believed that eating soy would increase your risk of breast cancer. But cancer research debunks this. Not only does eating soy not increase your risk of getting breast cancer, as Dr. Neal Barnard of Physicians Committee for Responsible Medicine points out, “it does the opposite, it reduces risk.”
So how did we get this wrong idea about soy and breast cancer in the first place? Isoflavones are plant estrogens found in soy. We know that high levels of estrogen increases breast cancer risk so it was thought these plant estrogens would do the same. The initial studies suggesting a link between increased breast cancer risk and soy consumption were done in mice. And while breast cancer risk was increased in the mice with higher soy consumption, it was later discovered that rodents and humans metabolize the isoflavones found in soy differently. While isolfavones are structured similar to human estrogen, these plant estrogens bind to the body’s estrogen receptions differently, and function differently.
According to the American Institute of Cancer Research, “population studies don’t link soy consumption with increased risk of any cancer.”
And observational studies in Asian women (many of whom consume lots of soy and many of whom consume no soy) link moderate soy consumption (one to two servings a day) with lower breast cancer risk.
It’s yet another health myth that women who’ve already had a breast cancer diagnosis ought to steer clear from soy. What does the research show us? That after a breast cancer diagnosis women who consume soy actually have a better chance of survival — a 21% reduction in all-cause mortality and continued remission -- than women who don’t eat soy.
What about women with a higher genetic susceptibility to breast cancer, like those with mutated BRCA genes? BRCA genes, when functioning properly, produce tumor suppressor proteins to help repair damaged DNA and can prevent cancer from forming. Certain genetic mutations in BRCA1 and BRCA2 increase the risk of breast and ovarian cancers in women. But studies suggest women with mutations on their BRCA1 or BRCA 2 genes can benefit from soy consumption as well.
Ok, so soy doesn’t increase breast cancer risk — and actually protects against it, potentially even for those with mutated BRCA genes. All good news! But let’s shift to the men in the room for a second and talk about how soy may affect them. Specially, does eating soy lead to “man boobs” or gynecomastia, a condition that makes breast tissue swell in males.
Again, this common soy myth comes back to our misunderstanding of the estrogen-like isoflavones found in soy. Estrogen is a female hormone and when we hear that the isoflavones in soy show estrogen-like activity, some men may worry this means they’ll experience an increase in feminized traits, like gynecomastia.
Luckily, science shows us this isn’t the case.
A review in 2010 looked at Asian populations, where soy is consumed in large quantities by men and women, and found that “soybean isoflavone exposure does not have feminizing effects on men.” And this study followed babies and children who’d been fed soy from an early age, which also showed no hormonal effects after long-term soy consumption.
Reducing your risk for breast cancer is just one of the health benefits of eating soy. Some other benefits include:
- Soy contains phytonutrients, which may lower your risk for developing disease in general.
- The isoflavones found in soy are also linked with reduced risk for endometrial cancer and prevent bone loss in women.
- Soy is naturally cholesterol free and low in saturated fat, which makes them a great meat alternative for vegans looking to get their plant-based protein.
- Soy foods contain fiber, which is great for boosting gut health (where our immune system lives!).
- Soy is high in omega-3s, an important fatty acid that can reduce your risk of heart disease and boost your skin and hair health.
You may have noticed “soy protein isolate” listed in the ingredients on many processed foods, from some brands of veggie burgers to protein bars. Soy protein isolate, or SPI, is a processed form of soy that’s made when the fat is removed from soybeans, leaving behind only the protein component and none of the fiber, minerals, and complex carbohydrates that make soybeans such a healthy plant-based protein choice.
Not to mention, the way SPI is often chemically processed raises some eyebrows in the nutrition community, as there can be trace amounts of unhealthy additives like aluminum and hexane. Hexane, is a petroleum byproduct of gasoline refining. It’s also found in glues, inks, varnishes, and some cleaning agents...not exactly something you want to be chowing down on.
The omnipresence of soy protein isolate in unhealthy processed foods often contributes to misconceptions about soy. Whole food sources of soy are a different animal altogether, nutritionally speaking -- with all their nutrients intact and none of the additives.
When it comes to your whole food plant-based diet. It's best to consume organic non-GMO soy (any soy that says “organic” is also non-GMO, by the way). And again, be sure to choose soy foods in their whole form or minimally processed. These healthier choices include:
- Soy beans (edamame)
- Low sodium Tamari
- Soy milk (need help finding the right non-dairy milk for your needs? Read this blog!)
- Chocolate Peanut Butter Shake - Click here for chocolate shake recipe
- Vegan Breakfast Benedict Recipe - Click here for vegan breakfast recipe
- Oil free vegan fried rice - Click here for fried rice recipe
- The ultimate plant-based protein shake - Click here for protein shake recipe
- Tamari mushroom stuffed sweet potato - Click here for the sweet potato recipe
As can be the case with any food, some people just don’t tolerate soy. About 1 in 2,000 people report soy allergies, which is about 40 times less common than those suffering from the most common food allergy, dairy milk. But if you do fall into the soy allergy camp, by all means avoid it! And if you just plain don’t like it, that’s OK, too. You do not need to eat soy to have a well-rounded plant-based diet.
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- Eating soy does affect your risk for cancer -- it decreases your chances of developing it and even can help survival rates for women already diagnosed with breast cancer.
- Soy consumption is not linked with gynecomastia, or swelling of the breast tissue in males.
- Eating soy over meat can help reduce your risk of developing serious diseases, like heart disease. Soy consumption is also linked with decreased risk of bone loss and endometrial cancer in women.
- Not all soy foods are created equally! Processed soy protein isolate is found in many common processed foods, from veggie burgers to protein bars, and should be avoided on a whole food plant based diet.
- A whole food plant based dieter should enjoy whole or minimally processed forms of organic non-GMO soy, including soybeans, soy milk, tempeh, miso, and tofu.
- You don’t HAVE to eat soy to enjoy a healthy whole food plant-based lifestyle -- it’s merely one option of healthy foods to add to your plate.