How Soy Can Kill You and Save Your Life

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EATING SOY CAN KILL YOU! Scan the media reports and surf the Internet, and you’re bound to come across scary claims that would lead you to believe this is true. You may have heard:

  • Soy will give you breast cancer.
  • Soy formula is dangerous to babies.
  • Genetically modified soy foods may modify you.
  • Soy foods block your thyroid function.
  • Soy prevents the absorption of minerals and interferes with digestion.
  • Tofu causes Alzheimer’s disease.

As some of you may be aware, I often recommend soy as part of a whole foods diet. Many people question why I include these foods in light of such startling media coverage on the dangers of soy. The reason is relatively simple.

I have reviewed reams of research and many claims for and against soy foods. From the studies available, I can tell you that soy is neither as good as the proponents say, nor as evil as the critics claim. I wish we had more convincing science to report, but we don’t. The key is to take all the available evidence together and see what shakes out.

In today’s blog I have done that for you. I will review some of the recent data for and against soy, and provide you with a few guidelines and things to remember when choosing soy foods.

What the Data Says about Soy

If you want an excellent, unbiased, scientifically sound review of all the relevant human data on soy, I recommend reading the 100-page report from the Agency for HealthCare Research and Quality entitled, The Effects of Soy on Health Outcomes, which reviewed thousands of studies based on rigorous criteria for scientific validity. Its conclusion was this: There is no evidence of significant benefit or harm based on the quality of evidence that exists today.

The dangers of soy are overstated. The benefits may be too.

So what’s a confused consumer to do? Give up on soy until we know for sure? Or chow down on soy nuts? Don’t panic. There are some things we do know about soy, both good and bad.

First, you should be aware that the amount of soy used in many of these studies was much higher than what we normally consume — the average dose of soy was equivalent to one pound of tofu or three soy protein shakes a day. That’s a lot of soy! Most people just don’t eat like that. So when you read negative things about soy, remember that many of those claims are based on poorly designed studies that don’t apply to real-world consumption.

You could apply that thinking to other studies, too — like those that show that broccoli contains natural pesticides or that celery is high in toxins. Sure, those foods might cause you some problems — but not in the amounts that most of us eat. The same is true for soy.

Second, it’s important to recognize that many of the common claims about soy simply don’t pan out when you look at the evidence carefully. Let’s review four of these claims and the science behind them so you can have a better understanding of the real relationships between soy consumption and potential health threats.

#1 “Soy Causes Breast Cancer”

Because soy foods contain natural plant compounds (called isoflavones) that appear to work like hormones, some people worry that they could increase hormonally driven conditions like breast cancer. But that doesn’t seem to be the case. In fact, research findings (i) suggest just the opposite:

  • All population studies (studies of groups of people) of soy either show reduced breast cancer risk or no effect.
  • The only studies to show increased cancer risk are on mice with no ovaries or damaged immune systems who eat high amounts of processed soy.
  • Studies in mice WITH ovaries and functioning immune systems show inhibition of tumor growth.
  • Mice studies may not reflect the effect of soy on humans (in case you didn’t notice, mice and humans are not the same species).
  • High breast tissue density is linked to a higher risk of breast cancer. Breast tissue density increases with estrogen replacement, but decreases with isoflavone consumption in postmenopausal women. That’s a good thing.
  • Eating soy foods at an early age (childhood and the teen years) appears to have a significant protective effect against breast cancer.

If you really want to reduce your risk of breast cancer, drink less alcohol and eat less trans and saturated fats — all of these compounds may raise risk in high amounts. If it’s a choice between chicken nuggets and tofu, I recommend tofu!

#2 “Soy Formula Could Harm a Baby’s Development”

Some 20 million infants have used soy formula since the 1960s — but some people are concerned that the isoflavones it contains could affect a child’s growth and reproductive development. Yet the only large, long-term study on humans, published in the Journal of the American Medical Association, (ii) found that there were no major health differences in 811 men and women between the ages of 20 and 34 who had been fed either soy or milk formula as infants.

More recently, a report issued by the National Toxicology Program Center for the Evaluation of Risks to Human Reproduction concluded that there just isn’t enough human or animal data to say for sure whether soy formula harms a baby’s developmental or reproductive health.

So what should a mother do? First, breastfeed if at all possible, for as long as possible — ideally until your child is one year old. If that’s not possible and you have to use soy- or dairy-based formula, don’t beat yourself up about it. If there are any risks, they are likely to be very small. Hopefully, continuing research will shed more light on this question.

#3 “Soy is a Thyroid Poison”

I think this claim makes a mountain out of a molehill. Yes, there’s no doubt that soy can affect your thyroid gland — the real question is, how much does it take? If you’ve read that soy is bad for your thyroid, you’re probably reading claims based on a few poorly-designed studies that have been blown out of proportion.

Instead, consider this: A review of the research found no significant effects of soy on the thyroid except in people who are iodine deficient — a condition that is rare in this country.

Another well-designed study in the American Journal of Clinical Nutrition (iii) studied the effect of realistic amounts of soy protein on hormones, including thyroid hormone. It found that soy had no significant effects on these hormones.

Based on my assessment of this and other research, I am convinced that normal amounts of traditional soy foods pose no risk to thyroid function.

#4 “Fermented Soy is Better than Non-fermented Soy”

Now here’s a claim that DOES have some basis in fact. That’s because soybeans — along with other beans, nuts, and seeds — contain compounds called phytates, which bind to minerals inside your body and contain some potentially harmful compounds.

The Asian cultures that have traditionally consumed soy typically ferment it first. This process breaks soy down and makes it easier to digest. Plus, fermentation adds extra nutrients and probiotics (“good” bacteria) to soy. For these reasons, I prefer fermented soy foods, like miso, natto, tempeh, tofu and some brands of soy milk.

So, should you eat soy? My answer is YES — but with two very important guidelines:

  1. Say YES to whole, real soy. The Okinawans are the world’s longest-lived people, probably in part because of their diet. For more than five millennia, they’ve eaten whole, organic and fermented soy foods like miso, tempeh, tofu, soy milk, and edamame (young soybeans in the pod). One to two servings a day of any of these foods are fine.
  2. Say NO to processed soy. That includes soy protein isolate and concentrates, genetically engineered soy foods (typically made from Monsanto’s Roundup soybeans), soy supplements, and soy junk foods like soy cheese, soy ice cream, soy oil, and soy burgers. They don’t have the thousands of years of traditional use that whole soy foods do, are processed, and contain unhealthy fats and other compounds. I have real concerns about these types of soy.

In truth, good human studies on soy are limited, but those we do have suggest that soy may help lower cholesterol, prevent cancer, increase bone density, protect the kidneys of people with diabetes, and relieve menopausal symptoms like hot flashes.

When you are considering the media reports about soy, here are some things to remember:

  1. The dangers of soy are overstated (and the benefits may be, too).
  2. We eat far too much processed soy (and processed foods in general). Stay away from those in your diet including soy protein concentrates or isolates, hydrolyzed or textured vegetable protein, hydrogenated soy bean oil, non-organic sources of soy, and soy junk food like soy cheese and ice cream. Don’t eat them.
  3. Whole soy foods can be a source of good quality protein and plant compounds that help promote health.
  4. Eat only organic soy. Stay away from genetically modified versions.
  5. Replace soy oil with olive oil, fish oil, nuts, and seeds.
  6. Breastfeed your child. I prefer that no one feed dairy or soy formula to their babies, but if you have to, try not to worry about it.
  7. Don’t worry about soy’s effect on breast cancer if you eat it in the forms and amounts I recommend. It has even been shown to protect against breast cancer if you start eating it at a young age.
  8. The effects on the thyroid are not significant or relevant unless you are deficient in iodine (which you can easily get from eating fish, seaweed or sea vegetables, or iodized salt).

I’m eager to see more research on the effects of soy on our health. But as we wait for more studies, there’s no need to pass up this healthful and delicious food. It can be safely included as part of a whole foods diet — which is one of the most important keys to lifelong vibrant health.

Have you experienced any health problem because of eating soy?

Have you experienced any health benefits from consuming soy?

Do you agree or disagree with any of the arguments about this controversial subject that I’ve listed?

Let me know your thoughts by leaving a comment below.

To your good health,

Mark Hyman, MD

References

(i) Messina, M. 2010. A brief historical overview of the past two decades of soy and isoflavone research. J Nutr. 140(7): 1350S–4S.

(ii) Strom, B.L., Schinnar, R., Ziegler, E.E. et al. 2001. Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood. JAMA. 286(7): 807–14.

(iii) Persky, V.W., Turyk, M.E., Wang, L. et al. 2002. Effect of soy protein on endogenous hormones in postmenopausal women. Am J Clin Nutr. 75(1): 145–53.

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28 Responses to How Soy Can Kill You and Save Your Life

  1. Maria April 1, 2013 at 7:43 pm #

    What about non-GMO soy lecithin. Is it rich in isoflavones and is it bad for the thyroid?

    • Avatar of Dr. Hyman Nutrition Staff
      Dr. Hyman Nutrition Staff April 5, 2013 at 3:30 pm #

      Hi Maria,

      If you have a sensitivity to soy than you might note a reaction. Typically, soy lecithin has higher amounts of omega 6 fatty acids, lower anti-inflammatory omega 3. This might provoke a reaction if you are very inflamed. This being said, it is best for you to note how your particular system responds to it by keeping a detailed food journal such as the one suggested by Dr Hyman in his book, The Blood Sugar Solution.

      For more personalized nutrition advice, Dr Hyman’s nutrition coaching team would be happy to work with you on an individual level to help you reach your goals. To work with the nutrition coaching team please go to:http://www.bloodsugarsolution.com/nutrition-coaching/ OR call (800) 892-1443 to get started.

  2. Claudia April 2, 2013 at 4:25 pm #

    Dr. Hyman, could you please specify the brand sof soymilk that you DO recommend? Thanks!

    • Avatar of Dr. Hyman Nutrition Staff
      Dr. Hyman Nutrition Staff April 5, 2013 at 3:56 pm #

      Hi Claudia,

      To see the brands that Dr Hyman likes, please go to: http://www.bloodsugarsolution.com/links/
      For more personalized nutrition advice, Dr Hyman’s nutrition coaching team would be happy to work with you on an individual level to help you reach your goals. To work with the nutrition coaching team please go to:http://www.bloodsugarsolution.com/nutrition-coaching/ OR call (800) 892-1443 to get started.

      • Michele July 16, 2013 at 2:32 pm #

        help! … I went to the link you provided (above) to see Dr. Hyman’s recommended brands of soy milk … there is a “beverages” category that doesn’t allow me to click-on it to get to the information! … help! … thank you

  3. Dipa April 13, 2013 at 3:58 pm #

    Hi, what are your thoughts on Metagenics ultra meal plus 360? It contains soy isoflavones as its protein source.

    • Avatar of Dr. Hyman Nutrition Staff
      Dr. Hyman Nutrition Staff July 12, 2013 at 11:27 am #

      Hi Dipa,

      This is a great protein powder for your shakes depending on your ultimate health goals. What are you looking to achieve?

      For more personalized nutrition advice, Dr Hyman’s nutrition coaching team would be happy to work with you on an individual level to help you reach your goals. To work with the nutrition coaching team please go to:http://www.bloodsugarsolution.com/nutrition-coaching/ OR call (800) 892-1443 to get started.

  4. Antionette April 13, 2013 at 8:29 pm #

    I know a little bit about soy and have seen some benefits. But, recently was told that soy should not be a part of my diet due to me going through menopause. I beg to differ. i don’t consume that much at all. Maybe in smoothies and very seldom use soy milk. I take Iodine Plus 2, Vitamin D3 with Krill oil together to prevent inflammation, SuperC22, several B’s at different times, Cal Max, seldom eat meat, love fish and some chix. The rest in fruits and vegeatables. Seldom eat pasta or bread unless I splurge

  5. Antionette April 13, 2013 at 8:33 pm #

    What kinds of soy other than Organic Milk could I eat? I’m 50 years old. Thanks

    • Avatar of Dr. Hyman Nutrition Staff
      Dr. Hyman Nutrition Staff July 12, 2013 at 11:25 am #

      Hi Antionette,

      Eat whole food-based soy products that are labeled as NON-GMO and preferably organic, if possible. Try edamame, tofu, miso or tempeh. If you are interested in learning more about these foods or how to prepare them hop on over to Dr. Hyman’s nutrition coaching for more guidance.

      To work with the nutrition coaching team please go to:http://www.bloodsugarsolution.com/nutrition-coaching/ OR call (800) 892-1443 to get started.

  6. Geraldine August 2, 2013 at 8:21 am #

    Thank you for this informative article but I’d like to know the effects of traditionally prepared Soy formular on an infant. I exclusively breast fed my baby for six months and since last week been feeding her on cereals mixed with soy formular. I made it myself using soybeans, crayfish, oven baked unripe plantain and a little quantity of peanuts. Am nigerian and it is common here. I was alarmed when I accidentally read abt all the evil sides of soy. Though this article has relieved me ssomewhat.

    • Avatar of Dr. Hyman Nutrition Staff
      Dr. Hyman Nutrition Staff August 16, 2013 at 2:54 pm #

      Dear Geraldine,
      Thank you for your interest in Dr. Hyman’s work. Is your infant responding well to the formula? Dr. Hyman would suggest using NON-GMO soybeans if possible. If you would like to work with Dr. Hyman’s nutrition coaches, please hop on over to:http://www.bloodsugarsolution.com/nutrition-coaching/ OR call (800) 892-1443 to get started.
      In Good Health,
      The Nutrition Team

  7. shay August 9, 2013 at 1:05 am #

    Good article. I appreciate your balanced advice. I was struggling with low thyroid that was undiagnosed. Looking back, I still have no clue why my dr never checked my thyroid. I know my thyroid was low because my hair was thinning and I lost the majority of my right eyebrow when I was 30. After being diagnosed with fibromyalgia, I began eating a whole foods diet which was a huge improvement in my health. But still no eyebrow. 2 years ago I started making green smoothies with organic soy milk, green leafy veggies and sea greens. I drink one per day. Not only did my eyebrow fully come back, my hair has gotten so thick my hair stylist has to thin it out with thinning shears or I look like one of the Beatles (I have short hair ) For me the results have been dramatic. I do not use a lot of soy, but I try to get in one serving per day.

    • Carole November 16, 2013 at 2:02 pm #

      Hi Shay,

      I was wondering how old you were when your hair became very thin and your right eyebrow more or less disappeared? Also, what green leafy veg did you use and what are sea greens (?) for the smoothies you drank per day? My hair has gone very thin but I think its medication that has caused it. But I wouldn’t mind trying what you did to see if I got a similar result. I am however, in my early 60′s and wear a wig if I go out, which isn’t very often.

      Thanks,
      Carole

  8. Mallika September 1, 2013 at 2:11 pm #

    Hi,

    I get soy chunks (nuggets) which I roast and eat. I don’t get so tired or my feet don’t hurt so much if I eat about a cupful of these roasted nuggets. But I have heard soy is very bad for the pancreas. Can I continue eating soy in this manner?

    Thanks!

  9. steve October 5, 2013 at 7:23 am #

    You know I love science,but I see a flaw in modern science as well. Knowing how big money influences most things, to me it seems it also influences science, what is known, or allowed to be known, and what studies get the most publicity. Which makes it hard to sometimes figure out the real truth. Perhaps everything has pro`s and con`s but which is publicized the most seems to relate to which has big money behind it.

  10. Joey October 11, 2013 at 1:13 pm #

    It seems easier to just cut Soy out of your diet.
    Anytime I hear “as long as you dont have a certain amount,” I question it.
    That amount, which we dont know the quantity of, has different effects on different people.

  11. Malika November 14, 2013 at 8:34 am #

    I used lasco soy milk instead of milk for 2 weeks without sugar adding sugar and i lost 30 pounds also ate whole grain products and limited oil to olive oil for that same period… but even with my pms.. when i started bk the milk i got pms symptoms like cramps n bloating up 2 2 weeks before it periods n bad migraines… poor skin acne n discoloration i started bk my soya 2 months now n no bad tummy aches or headaches and skin cleared up hugely…. so yep n i lessen my meat intake and eat veggie or beans n on an off soya chunks and chicken breast… n still use oil n flour…. so yep i love soya…

  12. Jonathon - Food Scientist December 9, 2013 at 11:39 am #

    Generally tofu and edamame are NOT fermented and therefore have a lot more of the dangers of soy. Stick with tempeh, miso, and natto.

  13. Gianca December 11, 2013 at 3:51 pm #

    I have been using now for one month a new product at GNC called Vege Fuel. It is a soy based protein powder. It is working well for weight loss and muscle health. I have no complaints so far and the improvement seems to be compounded each week. I still eat healthy and well balanced. I have a shake with water and cacao for taste first thing in the morning then 3.5 hours after, Then 3.5 hours after I eat normal. My diet is based on the Qivana diet which was designed by Dr. Layman, head of nutrition at Illinois University. In any case I am wondering if i am having too much…

  14. Lareena Groves December 30, 2013 at 12:46 am #

    Thank you Dr Hyman for your balanced review on soy research. I have been consuming soy products for 22 years (vegetarian for 27 years).
    I became aware of danger alerts that seemed to gain momentum about 15 years ago. Many high profile health experts whom I have great respect for and follow much of their advice, are alarmist in their attitude towards soy. I decided to trust intuition and my own reasoning, so hence I am so very grateful to stumble on your well considered report.

    My diet consists of a wide variety of organic, whole plant foods and whilst soy is definitely in the mix, it doesn’t over dominate and which includes: soy milk, miso, tofu, tempe and tamari sauce. To be honest I didn’t feel that much different switching from animal proteins to vegetable proteins, the transition for my body was easy. Is it because I am Type A blood type ?? However when I gave up dairy a few years on, the difference was profound. My energy levels skyrocketed, and basically I never knew that I was sluggish because that was what normal had always felt like. Omitting dairy meant that I switched to soy milk.
    I enjoy good health without the consumption of flesh foods or dairy, had a blessed pregnancy, birth and breastfeed for 2years with plenty of milk supply. My daughter is now 14 and has never eaten meat, vegan for first 7, now has home eggs since became available to us and rarely eats dairy. She has above average health, no allergies, or anything to remark on, rarely gets sick… is tall and not emaciated. All the things she shouldn’t be according to all the advice???

  15. Meneta Deaton April 28, 2014 at 2:22 pm #

    I am glad to see the discernment between processed soy and other versions, like fermented. Soy is a term that covers a lot of different things. My experience was that I ate a lot of Kashi products, particularly the bars, often one at breakfast and one at lunch. They contain the soy protein isolate as the protein source, as do many bars that profess to be high in protein. My thyroid production became an issue (low), so they put me on meds, with little change. When I cut out the bars with soy protein isolate, my body’s production went back up, so they took me off the medicine. My thyroid has been fine ever since.

  16. Jack May 9, 2014 at 6:39 am #

    Dr. Hyman, I have been doing a lot of things to reduce blood pressure. One breakfast item I saw on a list of recommendations for this was a smoothie made of a banana, blueberries, juice or skim milk, ice cubes, and a scoop of SOY protein powder. What do you think?

    Also, you are a male. So why is there a picture of a blond woman with all your responses here?

    Jack

  17. Belinda May 18, 2014 at 9:20 pm #

    I live in NZ where Iodine deficiency is more common. I drank soy for all of my 20′s and by my early 30′s was on 200mcg of Thyroxine per day. FYI.

  18. Bea June 25, 2014 at 2:30 am #

    Dear Dr. Hyman,

    Thank your for your considered report on soy. I have avoided soy for some years due to hearing of its dangers. I have several friends who ate tofu and soy milk all the time and got breast cancer. Of course they didn’t eat enough green vegetables either. For myself I never ate that much soy, and have all along eaten a lot of vegetables. However recently I have discovered I react to many foods due to severe histamine and gluten sensitivity and a couple of bouts of over strong antibiotics a few years ago. Strangely enough, now when I eat sprouted organic tofu, it gives me a noticeable boost. Perhaps because I am well past menopause? It feels like there is something in it my body needs. I can’t have fermented food except for plain yogurt, so I avoid fermented soy. I am glad I can have a bit of tofu now and then without having to worry that it may bring on cancer or some other dread disease. I don’t get soy in my diet otherwise since I cook everything from scratch and throw it out if its over two days old. I also don’t eat much meat these days due to its high amine content which unfortunately usually gives me a migraine. Ditto with fish unless I catch it myself and cook it almost immediately. Fortunately I don’t seem to have any kind of allergic or sensitivity response to fresh sprouted organic tofu. Weird eh? Since soy is so highly allergenic. However I have used nattokinase capsules (which are derived from fermented soy) to good effect for years, so I guess I just am not allergic/sensitive to it.

  19. Laurie Holbrook June 27, 2014 at 3:09 pm #

    I’m allergic to soy and it has terrible consequences for me. So I personally am disgusted that they are putting soy in everything and they aren’t required to let you know. Only veggies and fruit for me now.

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