Is Soy Safe?

Soy. For some, it’s declared as a heaven-sent meat alternative. For others, it’s a cancer-causing villain. The pervasive mystery surrounding soy is there for good reason. There are literally thousands of papers published on the topic. So let’s explore the mystery surrounding soy and answer the question: Is soy safe?

Soy Nutrition

Soy comes from soybeans, a vegetable in the legume family. The beans may be harvested early when they’re still green (also known as edamame), or when they’re mature and a light brown color. They can be cooked and eaten whole or processed into a number of different products including soymilk, tofu (the “cheese” of soymilk), miso, tempeh (a fermented whole soybean product), soy nuts, and soybean oil.

Soybean’s most famous characteristic is its protein content, making it super popular among plant-eaters. It’s comparatively higher in protein than many other vegetables and the amino acid content mimics what humans require, making it a sought after protein source for vegetarians and vegans. Soybeans are also higher in fat than other beans and contain both essential types of fat, omega-6 and omega-3, with the majority being the unsaturated omega-6. The type of carbohydrates found in soy promotes healthy growth of intestinal bacteria by providing the bacteria with a food source. Soy is rich in other nutrients as well; it contains iron, folate, vitamin C, potassium, magnesium, and calcium as well as certain phytochemicals that have been shown to kick-start your health. (1, 2, 3)

Soy and Health

Soy has curiously been touted to both prevent and cause breast cancer. This stems from the fact that soybeans contain a uniquely high amount of a group of phytochemicals called isoflavones. Isoflavones from soy have some estrogen-like properties and can act similarly to estrogen in some circumstances or have anti-estrogen effects in other circumstances. Critics of soy claim these estrogen-like properties may be harmful to those at risk for breast cancer, however, the most recent evidence does not point to this.  Some evidence has even suggested that soy isoflavones may be beneficial for those with certain breast cancers. Even more compelling research suggests that women who consume soy in childhood and teen years have a lower risk of developing breast cancer later in life. The bottom line here is, at a minimum, we don’t have good evidence to show that whole soy foods are unsafe for healthy women and they may actually have some benefits. There is less evidence available when it comes to isolated soy protein—protein that has been extracted from the whole soybean—which is often found in soy protein supplements and soy meat alternatives like veggie burgers. (1)

Women are not alone in reaping the health benefits of soy. It has been shown to reduce cholesterol, a risk factor for heart disease, although whether this translates to a lower incidence of heart disease events (like a heart attack) is still unclear. Isoflavones may also help protect the arteries. Considering heart disease is, globally, the number one killer, that could mean powerful things. Other potential benefits involve improved bone health and prostate cancer reduction, although it’s likely your intake of soy needs to be lifelong to get the bone boost. (1)

What should I eat? 

So, let’s say you want to start chowing down on some soy. What’s the best soy food to eat? Vegan for Life (1) suggests we take some guidance from traditional Asian diets, where people have thrived eating soy for over 1,000 years. In fact, residents of Okinawa Island, Japan—where soy is eaten on the daily—are famous for having the longest disability-free lifespan in the world. (4) The main sources of soy in traditional Asian diets are tofu, soymilk, edamame, and the fermented foods miso, tempeh, and natto. These are the soy foods I would suggest including in your diet. Make sure to keep an eye on the ingredient list of soymilk; I would choose a brand without added sugar or flavoring. I also recommend choosing organic soy products or those labeled non-GMO whenever possible.

What about all those meat alternative products like veggies burgers and the like? They generally contain soy as soy protein isolate. While there is no reason to believe the isolated protein is harmful, it may not have some of the same benefits as the whole food would. (1) There are also a wide variety of soy meat alternatives available that contain a wide range of ingredients. I recommend reading the ingredient list and choosing those with the fewest ingredients as well as ingredients that you recognize. While meat alternative products can be included in a healthy diet, I would suggest less-processed versions of soy like tempeh, edamame, soymilk, tofu, and miso. Or you can experiment with homemade meat alternative recipes and you’ll know exactly goes in ’em. (Try Emma’s Spicy Edamame Burger recipe for a yummy start.) As far as how much you should eat goes, there is no official requirement for soy in our diet. If we look to traditional Asian diets for clues, I would suggest 1-3 servings per day.

Now that you have some info, I hope you can make an informed decision as to whether soy is right for you. I believe soy can certainly be part of a healthy diet. As with many things in my diet, my goal is to eat it in a form as close to the way I’d find it in nature. In soy’s case, that means whole soybeans, usually as edamame. Soymilk, tempeh, tofu, miso (or even natto if you’re adventurous) have a little more processing but can add a healthy variety to a plant-based diet. Soy has been cultivated and consumed for over 1,000 years and I see no reason to stop anytime soon.

xo. Lindsey

A note from Sarah:

Great job, Lindsey! As previously mentioned, soy contains both omega-3 and omega-6 fats, predominantly the latter. Soybean oil, considered a vegetable oil, is one of the most commonly used oils in processed and convenience foods, thanks to its high smoke point and cheaper price tag. Omega-6 fats are polyunsaturated and, in excess, can be pro-inflammatory. While inflammation isn’t always a bad thing (inflammation helps heal cuts and wounds), too much of a pro-inflammatory food can be bad as it may worsen chronic states of inflammation now known to cause adverse conditions like diabetes, obesity and heart disease. So how much is too much? Recommendations are that we aim for a 1:1 ratio (omega-6: omega-3). Soybean oil falls around a 9:1 ratio (58% omega-6: 9% omega-3), yikes! Oils are highly concentrated and when consumed regularly, you’ll quickly find yourself exceeding the 1:1 recommendations. The best way to counteract this is to ensure you’re consuming plenty of healthy omega-3 rich oils—like flaxseed oil—while not going overboard with the omega-6 rich processed foods and oils.

Credits // Author: Lindsey Kelsay with contribution from Sarah O’Callaghan. Photo by: Emma Chapman. References: 1. Norris, J., Messina, V. (2011) Vegan For Life: Everything You Need to Know to Be Healthy and Fit on a Plant-Based Diet. Da Capo Press. 2. Melina, V., Craig, W., & Levin, S. (2016). Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. Journal of the Academy of Nutrition and Dietetics, 116(12), 1970–1980. http://doi.org/10.1016/j.jand.2016.09.025 3. USDA National Nutrient Database. Available at https://ndb.nal.usda.gov/ndb/ 4. Mishra, B. (2009) Secret of Eternal Youth; Teaching from the Centenarian Hot Spots (“Blue Zones”). Indian Journal of Community Medicine, 34(4), 273-275.
  • Thank you, thank you, thank you for this article!!!

    I had cancer from ages 7-13, and my treatments kinda caught my pituitary gland in the crosshairs off and on. I thank God I’m healthy now, but since treatment was during puberty, near that gland, and other hormonal-type cancers run in my family, hearing a few years ago that soy could be dangerous really alarmed me. I’m trying to manage my weight and be on the look out for potential long-term side effects, and had previously considered soy products a great alternative to some dietary items. Then I worried I’d been over-doing it and was afraid of damage done. This article is informative, easy to understand, and hit all the points I’d wondered about! Thank you so much!

  • This was super helpful. I’ve been conflicted over soy in my diet. It is true that soy’s been around for a long time so I will continue to buy my organic tofu for when I want to go meatless and munch on edamame! Makes sense to stay away from processed soy foods.

    In my early 20s I used to love eating anything soy based and would think I was being healthy in buying “better” processed food. But processed health food is still processed food in the end. Time to finally make some veggie burgers of my own so I know exactly what goes in them!

    • I did the same thing in my younger years! Looking back at some of the ingredients, I now realize they weren’t as healthy as I thought. Live and learn, I suppose. Thanks for reading!

  • I love love tofu, and enjoy incorporating it into my diet (especially as a vegetarian!). However, I’ve cut right back because I’ve noticed I always breakout when I have too much tofu or soy milk 🙁

    I only made the connection a few months back when I realised I was having 2-3 soy lattes a day – and if you consider a milk coffee more of a snack than a drink… that’s a lot of snacks!

    So I challenged myself to a month of black coffee only, and when I reintroduced the soy milk, I got a stomach ache and a huge crop of pimples on my chin 🙁 I’ve now noticed the pimples in the same spot each time I have a prominent serving of tofu (a small portion in a stir fry seems to be OK, whereas a tofu steak or tofu-based meals are not).

    So now I’m just choosy about what tofu meals I consume: “Will this be worth the pimples?” hahah! (And sticking with the black coffees – soy milk coffees are NOT worth the pimples when I enjoy black coffee so much!)

  • Thank you!!! Being a vegan means I’m surrounded by soy based products. This article cleared every question I had about it, so again, Thank you!!!!

  • I actually am sensitive to soy (especially soy protein). It messes with my hormones and causes my body to mimic an anxiety attack, which is very unpleasant! Just putting that out there, in case someone wanted an additional view!

  • So my mom used to drink soy milk as her dietitian suggested her to …but later she stopped as she read somewhere that soy milk may trigger hyperthyroidism. I’ll surely forward this post to her.

  • There is definitely a lot of contradictory information from a lot of sources. I don’t plan on cutting soy from my diet. I believe that since I don’t feel certain about any of the two cases either way, I’ll keep consuming it in moderation.

  • Thank you for this article, what perfect timing! I’ve recently started switching over to a mostly vegan diet and have been wondering a lot about soy. I love tofu but will keep an eye out next time for your recommendations.

  • I‘m not against soy and also consume it from time to time. I just think it’s beyond important to watch your product choice. Soy consumption is growing world wide and much rainforest has already been burnt down because of growing soy. This in my opinion is not how it’s supposed to be. So when I buy soy products I only choose the ones that are Fairtrade (or specifically produced with rain forest protection) or – living in Europe – produced in Europe. However Europe is not the best place for growing soy which makes me try to find alternatives like products from lupines for example.

  • As someone with a thyroid condition I am used to people telling me soy will kill me one weak and that soy will save me another. One of these ingredients no one will ever agree on, like milk 🙂

  • Thank you!
    My mom has also worried about soy after a cancer bout and my hunch was to go with the fermented traditional foods rather than the new fangled alternatives.

  • Yes I am so happy that you put the paragraph at the end saying that we should make our own informed decision about soy. There is so much conflicting information out there that I really think you just need to see what it does to your body and go from there. Tofu and soy milk are highly processed, whereas tempeh and natto are actually fermented, this actually increases the health benefits and means it is better for your gut 🙂
    I normally avoid soy as I feel that it makes my acne worse (due to those phyto-estrogens) but I love to chow down on edamame at a restaurant. Or add tempeh to my breakfast every once in a while!

  • This is such a great article. I am working on moving my family from a very processed fast food lifestyle to a plant based one. I was soo overwhelmed at first, but then I decided that a lifestyle is small steps. First I started by cooking at home. We’ve rotated from 90% takeout 10% at home to 90% at home, 10% takeout. We also planted an herb garden and now moved up to a veggie garden. Right now I am just starting cut back the meat in meals so everyone can see that the food can still be tasty! The other day I made a chili with very little meat and my husband loooved it, didnt even notice. Im also so excited to hear that edemame is ok, as the kids love it (something about popping the beans from their shells, haha). Thank you for all the information, these articles are very helpful for me to navigate this change.

  • Thank you ladies so much for sharing evidence based health information. There’s so many opinions out there on the internet with many that don’t hold any water, so it’s always great to read pieces that are carefully researched with appropriate sources cited.

  • There is some concern here in the UK that the oestrogen-like effects of soy *may* be a problem for those suffering from endometriosis; my friend was recently advised by her consultant to avoid it to be on the safe side. X

  • Thanks for sharing that information, I feel more enlightened than before! I definitely have been avoiding soy as my nutritionist warned against it, but you’re absolutely right about it being a normal part of diets in Asia. I think moderation in everything is key.

    Eva | http://www.shessobright.com

  • Interesting read. I’ve always been very curious about this topic when choosing proteins to drink after work out. I usually always try to avoid soy based proteins. Always like being more educated on topics like these! Thanks for sharing your knowledge

  • A caution for people adding a bunch of soy into their diets. Soy is one of the largest and fastest growing food intolerances/allergies out there. I can’t use a good portion of the beauty products on the market because I will break out in hives. I can’t eat at a lot of restaurants because my allergy is sensitive enough that soy oil (which is the majority of cheap “vegetable” oil on the market) will burn through my system. Soy intolerance/allergy presents mostly in gastric distress within a day of consumption. Be cautious always when changing your diet.

    • We also shared an article on milk and milk alternatives recently. Just click the “Ask a Dietitian” tab at the top of this post to see all the topics that have been covered.

  • Loving this series! Nutrition science for the win!

    Follow up question for you ladies: how does the fermentation process change the way our bodies processes soy? I’ve heard some praise tempeh and miso specifically because they are fermented products. Would love to know your take on this!

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