Kris Carr

Blog Post

Understanding How Soy Foods Impact Your Health

Hi Sweet Friends,

Oh, boy, we’re talking about soy.

It’s a hotly debated topic these days, especially in the plant-based community. You’ve probably heard mixed reviews on this elusive bean—some good, some bad and some very ugly. I know it can be frustrating, but don’t throw your tempeh piccata in the trash just yet. With a little extra smarts, you can make an educated decision on how, why and if soy should be part of your diet. I certainly include it in mine, but that doesn’t mean I’ll be signing up for a soy-dog-eating contest anytime soon. As you’ll learn in today’s blog, organic, non-GMO soy foods can provide many benefits when eaten in moderation.

What types of soy foods are best, and how much should you eat?

In my fridge, you’ll find a variety of whole and minimally-processed soy foods, such as edamame, tempeh, miso and tofu. These foods land on my plate 2-3 times per week, although I tend to use tofu the least since it’s one of the more processed choices in my soy repertoire. They’re all rich in nutrients, antioxidants, protein, essential omega-3 fatty acids and phytoestrogens. A word to the wise, almost all soy is genetically modified. That’s why I always buy organic and search for the non-GMO label. It’s best to look for both stamps of approval, since organic does not guarantee 100% GMO-free food.

Eating soy as nature intended (or very close to it) can be beneficial to your well-being in a variety of ways. Soy protein and omega-3s are important for heart health. They also keep your arteries clear and cholesterol levels low. And contrary to some unsubstantiated fear-based claims, phytoestrogens may actually help reduce breast cancer risk among premenopausal women (more on soy and cancer in the following section). In addition, whole soy foods are easier to digest and taste better than their processed cousins. Plus, the microflora in fermented soy products, such as miso and tempeh, are your belly’s BFF.

Again, keep processed soy foods (and processed foods in general) to an absolute minimum. You’ll often find soy protein isolate or concentrate — both at the top of my list to avoid—on their ingredient lists. Faux chicken nuggets, soydogs and other fake meats not only contain processed soy, but a laundry list of food additives and preservatives as well. While these foods aren’t the devil, they certainly aren’t real, and therefore should never be a dietary staple. Think of them as an occasional novelty. The one exception I’ll mention is for those transitioning from a meat-heavy to a plant-happy diet. Eating faux meats and cheeses as a crutch can be helpful, but they definitely shouldn’t hold center stage for long.


We often cling to processed soy foods because of our culture’s protein paranoia.

News flash sweet friends — protein doesn’t need to be the main event on your plate at every meal. Now I’m not saying that you don’t need protein, you absolutely do. But if you’re consistently eating a varied, plant-based diet, filled with beans, legumes, nuts, seeds, grains and vegetables, you’re in good shape! And with such an abundance of protein-rich choices in the plant family, are you starting to understand why soy is optional?

If you’re still concerned about protein, simply calculate your daily requirement using the following formula: Your body weight (pounds) multiplied by .36 equals the amount of protein (grams) needed for a moderately active adult. For example, a 140 pound person needs about 50 grams of protein per day. Here are just a few of the high-protein plant foods out there: one cup of lentils contains 18 grams of protein, one cup of quinoa contains 8 grams of protein and two tablespoons of almond butter contain 7 grams of protein. See how easy it can be to meet your protein needs?

Soy seems pretty straightforward when you’re talking about quality and quantity, but the conversation gets trickier when you begin to explore the claims flying around about soy and certain health issues. Next up, soy dangers demystified!

Is there really a link between soy and cancer?

You may have heard that eating soy increases your risk of cancers such as prostate and breast cancer, but the opposite may be more likely. Recent research has shown that lung cancer patients with a history of eating soy have a better survival rate than those who have eaten less or no soy in the past. Men who consume soy have actually been found to have a reduced risk of prostate cancer. And then there’s the most frequently misunderstood relationship — soy and boobs.

When a woman regularly eats protein-rich and phytoestrogen-rich soy foods, studies show that her breast cancer risk drops. Soy’s potentially protective role may be due to its isoflavones which are phytoestrogens (literally meaning “plant estrogens”) and may block some of estrogen’s activity. It could also be the result of various anti-cancer phytochemicals in soybeans. To get the maximum benefit of soy’s protection, some studies show that healthy soy foods should be part of the diet during puberty and adolescence when breast tissue is forming. But that doesn’t mean that you should go soy-crazy. As we’ve discussed, quality and quantity matter. For example, the ladies who participated in the original studies connecting Asian women’s lower breast cancer risk to their regular soy consumption were eating small, moderate amounts of whole or minimally processed soy foods (not buckets of soy jerky!).

So why are people still concerned about soy when it comes to estrogen-sensitive diseases like breast cancer? We’re still not sure how much soy is safe for individuals such as breast cancer patients and survivors, so doctors often recommend that their patients play it safe by avoiding soy completely. This is a very common approach because hormone-sensitive cancer receptors are stimulated by human estrogen and the structure of soy is similar to human estrogen. At the same time, eating soy foods can actually be beneficial to these types of patients and often recommended to patients in moderation during hormone blocking treatment. And it’s also important to mention that soy supplements (not soy foods) are frequently used in the animal studies that point an accusatory finger at soy and cause alarm.

In Life Over Cancer, Keith Block, Oncologist MD, states that based on his review of the current research, “both premenopausal and postmenopausal women with ER+ tumors can safely eat soy foods such as tempeh and tofu about two or three times per week.” Interestingly enough, many of the same doctors who tell patients to avoid soy altogether never mention the abundant amounts of estrogen and other growth hormones found in meat and dairy products! So if you’re avoiding soy as a result of a cancer diagnosis, think twice about animal products as well.

What about soy-loving fellas?

Good news for boys and men! Despite the buzz that “girlie” phytoestrogens may have a negative effect on hormones and fertility for males, there isn’t a single study showing this—nothing linking these issues to soy formula for baby boys or tofu burgers for boy scouts—nada. In fact, a huge study published in 2009 showed that soy food consumption actually reduced prostate cancer risk by 26 percent among soy-strong men. If you’re pregnant and concerned about soy affecting your baby boy, remember that any studies on the subject have involved animals consuming “large” or “high” amounts of soy—not something that fits into our model of eating a moderate amount of unprocessed, whole soy foods.

If you’re concerned about male reproductive issues, it might be time to look more closely at your dairy consumption. A recent study found that consuming high-fat dairy products like cheese and sour cream may lower sperm quality and fertility, perhaps due to the naturally occurring reproductive hormone, pesticides, chlorinated pollutants and/or heavy metals present in dairy foods.

Does soy impact thyroid health?

Another soy misunderstanding: Much like the confusion surrounding cruciferous veggies and thyroid function, soy isoflavones do not cause hypothyroidism or exacerbate hypothyroidism. Research published in the Journal of Clinical Endocrinology and Metabolism studied two groups of women: one group with 2 mg of phytoestrogens (plant estrogens in soy) and one group with 16 mg of phytoestrogens. They found a small percentage of the high-soy intake group had some decrease in thyroid function, but it should also be noted that the high-soy intake group also saw significant health benefits from this increased soy consumption, such as decreased insulin resistance, decreased inflammation markers and lower blood pressure.

You should be aware that soy isoflavones may absorb some of the iodine needed to make thyroid hormones, which could increase the body’s need for iodine. But, as long as iodine intake is sufficient, soy shouldn’t be a problem for the thyroid. Iodine is especially high in sea veggies, which means that miso soup with tofu cubes and wakame seaweed is not only a soothing combo, but also a match made in thyroid health heaven.

Please note that soy foods may affect the absorption of meds used to treat hypothyroidism. If you take medicine to treat hypothyroidism and love soy, check with your doctor so that your dosages can be adjusted accordingly. And still eat seaweed — it’s good for you!

If soy isn’t a great fit for me, what are the best alternatives?

While soy can be a convenient and healthy part of your diet, know that if you’re allergic (soy allergies are quite common), feel congested after eating it or need to avoid soy for other reasons, it’s not an essential part of a plant-based diet and can be eliminated without compromising your health. As I mentioned earlier, plant protein and essential fatty acids are found in a variety of beans, lentils, nuts, seeds, quinoa and whole grains. And soy-free milk, cheese and meat alternatives are widely available today. Be a label detective and choose products with a short list of ingredients you can pronounce. I opt for a variety of nut, seed and grain-based alternatives, such as almond milk, hemp milk, flax milk, nut cheese and grain meat.

For more soy schooling, check out these highly researched and credible resources:

Whether or not you decide to include soy in your diet is very personal decision that only you can make, but hopefully you feel much more prepared to make that choice with this knowledge under your belt.

Peace & edamame,

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  1. Aimee says:

    Awesome! Thank you. I was JUST thinking about this. I’ve seen a lot of negative press about soy lately. I don’t eat a lot of it but I was wondering if it would be best to cut it out all together. This helps immensely.

    Also – I just moved to Europe. I’m confused about the GMO laws here, which I know are tighter (thankfully!). I believe that if something has GMO in it then it must be labled as such, correct? If it doesn’t say it has GMO crops in it am I safe to assume it is GMO free? Does anyone know?


    • Louise says:

      Hi aimee,
      I don’t know about the rest of Europe in the UK we have all GMO food labelled. In Tesco supermarket, all their own-brand food is GMO free. We’re not keen on GMO here in the UK, and thankfully our stores listen to the public!


      • Nancy Nerem says:

        Foods containing GMO products do not need to be marked as such in the US. There have recently been attempts at passing legislation to accomplish this, but they have failed. As of now, you can safely assume that anything that is not marked “organic” has the possibility of have GMO products in it: especially corn and soy as these are the most prevalent GMO products…

  2. Chara says:

    This is helpful, Kris. The soy issue is confusing. I am not sure soy affects me well, but I’m going to reconsider. I entirely agree with you about avoiding processed and GMO soy. Love your blog and your leadership on dietary issues and health!

  3. Though soy, in its original state, is an incredibly high phytonutrient food, it is high histamine and therefore may cause rashes, bloating, migraines, severe inflammation and other allergy-like symptoms, especially in people who have histamine intolerance, mast cell activation and mastocytosis (but also in people who don’t). Obviously histamine induced inflammation is something you definitely don’t want to deal with in cancer as it can promote tumor growth (interestingly there are a number of studies looking into antihistamines shrinking tumors).

    As one of the quickest rising allergies in the world (likely because many of us lack the enzyme/s to digest it), it’s often the first thing I suggest people look at when they tell me they have weird allergy symptoms, with a negative IgE or RAST test.

    That said, edamame beans are my absolute favourite! How I miss them…

    LOVE your work and all the good you do for people.

  4. Angela says:

    Great article Kris – good on you for being brave enough to get stuck into this much debated topic.

    For info, another excellent and thorough review of the research can be found here:

  5. Jeannie says:

    Eating only fermented soy gets rid of the problems associated with the anti nutrients in soy – and in other pulses as well. Fermented soy is pretty easy to find, although natto is a bit of an acquired taste. Tamari, tempeh and miso are all great fermented products. For other pulses, just sprouting them cuts the phytic acid by about half and boosts the nutritional value – just takes a bit of planning ahead.

    But hardly anyone is going to be suffering from a shortage of protein as long as they’re eating nutrient dense foods, with or without soy. We know that over a long history, Asian cultures that traditionally have consumed quite a bit of soy tend to be long-lived, and for me that’s more convincing than conflicting study results. So for me, I include fermented soy because it adds variety and I do quite a bit of Asian fusion food. I rarely eat non-fermented soy, and absolutely never non organic – if it isn’t organic you are pretty much guaranteed to be consuming a GMO food. Don’t do that.

  6. This blog post is RICH with priceless information on soy: wow! I had wanted clarification about soy for a loooooooong time and having read so many different (conflicting) information, it was getting very confusing.

    I’m gonna share with with posse. Thanks Kris!

  7. Tracy says:

    Great article!
    I used to eat only organic local soy from a small farmer (
    I’m so afraid that Monsanto has gotten its dirty claws into most soy out there, but I felt comfortable with Vermont Soy after meeting the farmers and talking to them about my concerns.

    Recently I had a food sensitivities test done, and soy came up with LOTS of reaction! So…I avoid it now. Gosh, it’s in almost all packaged food!!!!!!!

    Thanx for the great articles, always, Kris!!!

    -Tracy C

  8. Claire says:


    I am a breast cancer survivor who was treated at Memorial Sloan Kettering and was told similar information to as what Kris has written. I am hoping this link to their nutrition pamphlet on healthy eating for breast cancer will work. If so, scroll to page 26 on soy.

    One thing they emphasize, which I also saw on Dr. Oz, is to avoid SOY PROTEIN ISOLATE, a highly processed version particularly harmful for estrogen-based cancers, and which lives sneakily in all kinds of unexpected places like crackers and energy bars. Here is the link to Dr. Oz:

    Kris, love receiving your articles every week!!

  9. This blog post is RICH with amazing information I absolutely needed. I’ve been reading so many contradictory information I was a little confused quite frankly.

    I love my edamame and I’m determined to find a recipe that’ll make tofu taste good (Yottan Ottenlenghi has a great recipe in his new book and I love yours in CSKitchen!) so your clear guidelines Kris and abundance resources above are really helpful.

  10. Janelle says:

    My concern with soy is that Americans consume ver large portions (tofu steaks ???). Most Asian cultures eat a much much smaller portion size.. Thoughts?

  11. Nancy says:

    I rarely use soy products now because of the Cornucopia report about hexane gas extraction, and when I do buy tofu, I buy organic, fermented tofu. I also consult Cornucopia’s list of brand names that use or don’t use hexane gas extraction before buying a soy-based product.

  12. Caitlin says:

    THANK YOU so much for this!

  13. Birgit says:

    Hi Glowy, thanks for the soy talk. I still am a little confused about it. There is a German food chemist named Udo Pollmer he is reporting that soy as such is poisoness and that it is weakening the immuno system. Unfortunately his Youtube things are in german. But he says that the benefits of soy are made up marketing tricks starting in the 50´s and he states that when you are trying to look up the studies for the health benefits on soy you actually find no study… This is all very confusing. Does anyone know something about it?

  14. Helen says:

    As ever, Kris you rock – this is a great de-bunk of the bad vibes about soy!

  15. Veronica. says:

    Thanks for a great article. As a nutritionist, I see lots of women actually gain weight when they increase their soy consumption – even the whole, organic forms. I’ve also seen many women’s hormone levels change, confirmed through saliva analyses – and not for the better. I think the safest soy is fermented and organic, period. Also, there is definitely truth to the harmful effects of conventionally raised meat and the hormones they contain, however, grass-fed meat (for those who eat meat) from local, humanely-raised and happy animals, is actually anti-inflammatory and contains anti-cancer compounds that have been well researched. There needs to be more discussion and openness from vegans and vegetarians to that truth, even if they decide to abstain themselves.

    • Jill says:

      I agree Veronica. I am a nutritionist too and like you, see a lot of women gain fat or fail to loose it when they are eating a lot of beans and lentils. Yes, for vegans and vegetarians there are plenty of protein sources and you definitely can get enough, but often then there is too high a consumption of carbohydrates, even if they are from whole food sources. Bottom line, fermented soy can be very helpful in fulfilling your protein requirements, but let’s all keep an eye on making sure we are not getting too many carbs, even from whole foods.

  16. Leigh says:

    What are possible symptoms of soy allergies? I think I may have one, as I switched to vegetarian from heavy meat-eating just recently.

  17. Laura says:

    Thanks Kris! I get asked by a lot of friends transitioning to a plant-based diet about tofu recipes — it’s important to know how many protein alternatives there are since, like you said, soy should be eaten in moderation.

    That said, I also know friends and family who avoid soy at all costs. I hope your article helps demystify some of the effects of soy.


  18. Jen says:

    I’m still unclear about the safety of whole soy foods during pregnancy. I’ve heard it can negatively affect a male fetus, but I’m not sure how much soy one would have to eat for it to be considered unsafe.

  19. Lynn Fisher says:

    Unless one is in menopause, soy should be avoided EXCEPT in the fermented form (and then only organic of course!) “The Whole Soy Story” is a highly recommended read on the science as well as the businesses behind soy.

    Unfermented soy has the following 10 adverse affects on your body:

    1. High Phytic Acid (Phytates): Reduces assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking, but only with long fermentation. High-phytate diets have caused growth problems in children.

    2. Trypsin inhibitors: Interferes with protein digestion and may cause pancreatic disorders. In test animals, trypsin inhibitors in soy caused stunted growth.

    3. Goitrogens: Potent agents that block your synthesis of thyroid hormones and can cause hypothyroidism and thyroid cancer. In infants, consumption of soy formula has been linked with autoimmune thyroid disease. Goitrogens interfere with iodine metabolism.

    4. Phytoestrogens/Isoflavones: Plant compounds resembling human estrogen can block your normal estrogen and disrupt endocrine function, cause infertility, and increase your risk for breast cancer.

    5. Hemagglutinin: A clot-promoting substance that causes your red blood cells to clump, making them unable to properly absorb and distribute oxygen to your tissues.

    6. Synthetic Vitamin D: Soy foods increase your body’s vitamin D requirement, which is why companies add synthetic vitamin D2 to soymilk (a toxic form of vitamin D).

    7. Vitamin B12: Soy contains a compound resembling vitamin B12 that cannot be used by your body, so soy foods can actually contribute to B12 deficiency, especially among vegans.

    8. Protein Denaturing: Fragile proteins are denatured during high temperature processing to make soy protein isolate and textured vegetable protein (TVP). Chemical processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines.

    9. MSG: Free glutamic acid, or MSG, is a potent neurotoxin. MSG is formed during soy food processing, plus additional MSG is often added to mask soy’s unpleasant taste.

    10. Aluminum and Manganese: Soy foods contain high levels of aluminum, which is toxic to your nervous system and kidneys, and manganese, which wreaks havoc on your baby’s immature metabolic system.

    • Lynn says:

      Mercola is not a credible source. The same website continues to claim a link between vaccines and autism. This article, however, is very comprehensive and weighs the pros and cons very well. Great read!

  20. Jacqueline says:

    Thanks for your fresh and clear approach. Interesting to learn that it’s soy supplements used in testing as opposed to food – definitely great info to look for when I read about studies citing ‘dangers of soy’.

    I like to treat soy mostly as a condiment, and will eat organic tofu maybe once a month or so. Usually at a restaurant when that’s their veggie option. It’s super-easy and soft finger food for the kids, and they love it too!

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