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:
- 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.
- 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:
- The dangers of soy are overstated (and the benefits may be, too).
- 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.
- Whole soy foods can be a source of good quality protein and plant compounds that help promote health.
- Eat only organic soy. Stay away from genetically modified versions.
- Replace soy oil with olive oil, fish oil, nuts, and seeds.
- 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.
- 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.
- 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.
Thank you so much for this blog, Dr. Hyman. I feel much less confused now about the good things about soy, and the bad things about it.
Hi,
I also thank you for everything you do! I am Bulgarian and your books are translated into Bulgarian and are very popular!
i’m a big fan of your work and your youtube videos. however, you mention “saturated fats can cause breast cancer”? there are certainly TONS of factors that come before satfat as risk for breast cancer, like vitamin D and iodine deficiency, smoking, omega-6 vs 3 ratio, chronic systemic inflammation, way too high amounts of carbs and fructose, etc etc. don’t tell me you’re still one the very outdated “saturated fat is bad for you and clogs your arteries” train, are you? that would cut my respect for you at least in half, to be honest
. pretty much every myth about how bad satfat is has been debunked since at least 10 years now, and often proved to do exactly the opposite, like the protectiveness of cholesterol and satfat against heart disease etc. if you want to do something good for your health, go lower in sugars and simple carbs, ans certainly NOT in saturated fat, which is a completely neutral, if not explicitly beneficial energy source for the body (in contrast to too much carbs, which cause all sorts of chronic diseases).
also, you say, don’t eat processed soy like soy protein isolate! i couldn’t agree more. but isn’t that exactly what’s in baby formula? soy protein isolate? i would NEVER give that to my child (if i had one).
Thank you for your blog, Dr. Hyman.I also hear about it,especially teenagers (boys)
said that they can get more obesity in their chest like small female breast for ingest
this special nutrients,
Thank you,
Magda.
At last! A sensible explanation of soy. I’ve been generally avoiding it, thinking the disadvantages outweighed the benefits. But I think I’ll start eating it again, in its fermented form at least. Thanks for not being an alarmist about soy!
I’m not sure what research you’re reading, Dr. Hyman, perhaps those funded and sponsored by the soy industry I suspect. You might try reading Kaayla Daniels, The Whole Soy Story. http://blog.wholesoystory.com/
I would also suggest the readers of this blog, do their own research including how soy milk and soy protein isolate are made. They are industrial products that are highly processed and created using toxic chemicals. There is a reason why many countries now have issued warnings regarding soy in respect to infants and women at risk for breast cancer.
Sorry Dr. Hyman, I think you are wrong about soy. I have read your book, The Ultra MInd Solution and I think you make many important points reagarding diet and health. The soy issue is one I think you’ve made a mistake.
Thanks for your article. I was finally diagnosed 10 yrs ago with hypo thyroid. Since then I’ve read so many conflicting articles about eating and not eating soy with my disease. I like soy and wanted to have it as a main source of protein but I’ve been voiding using it for years. I just recently decided since I’m doing well on my meds, I started eating soy and eliminated all animal products, so I’m glad I ran across your article.
I personally know 2 people, my son and a friend who bought their hyperthyroid down with soy. My son was young and I gave him soy based protein shake because he was on the borderline of hyper, in 2 weeks he was normal. My friend had been on anti-thyroid medications for 2 years because she was hyper and it would not come down. They were going to do irradiation, so I told her about soy and raw cruciferous vegetables, but she mostly did it with soy. The result was 2 weeks later she was hypothyroid and on thryoid hormone, but at least they didn’t kill her thyroid. I myself am hypothyroid, and I can eat about all of 5 soybeans before they make me go to sleep, I can have maybe 1 8 oz. glass of soy milk, etc., so what I do is avoid all unfermented soy because it is just not worth the affects it has on me. It is not all in my mind either, before I knew I had Hashimotos and before I heard/read anything about soy, I noticed the effects of soy on me. I noticed soybeans (raw like edamame) make me really tired. I used to get soy dumplings sometimes with this girl from work and we would split them for lunch, and without fail a couple of hours later I would be falling asleep at my desk. I can eat a TINY bit of tofu (and I do mean tiny). I really think that in this case Dr. Hyman, you should do more research because I think (from my own an my friends) experience you are very wrong. My Sister (who also has Hashimotos) has successfully used soy milk to bring her thryoid back to normal range when she was hyper. That is not to mention the tons of people I have met up with on the Internet with stories just like mine. I really think that hypothyroid people are best doing what I do, avoid all unfermented soy. There is plenty of fermented stuff, miso, tempeh, soy sauce, natto, etc., that you can eat if you really want soy, and fermented soy does not cause any problems.
One more comment, tofu, soy milk and edamame are unfermented; if I eat those things I get hypo even though I am on thyroid hormone. I actually had one MD/ND who wanted me to eat more unfermented soy and take a higher does of thryoid hormone to compensate, I told her no, I did not think that was a good idea at all. I have the bad affect if I eat more than 5 edamame, more than 1 oz. of tofu, or more than 1 8 oz. glass of soy milk in a day, which is not much, that is why I just don’t bother. I can eat a whole bowl of miso soup (as long as it does not have tofu in it) and not worry about it, why eat unfermented soy at all and have to worry about what I ate? If I don’t eat unfermented soy at all, there is no problem.
I just thought of one more thing I want to say, I think the processing of soy must be different in Japan. I say that because I was recently in Japan (last month) and we ate mostly sashimi, but one night we had sukiyaki at a fancy restaurant. It was mostly beef and vegetables but 4 pieces of tofu (about 2 oz. each) were included. I decided to try just one piece of tofu to see how it would be (in comparison to tofu here in the USA). To my surprise, I didn’t notice any effect from it (normally I would have a reaction to that much tofu), so I think there must be something different in the processing methods that makes the Japanese tofu superior quality (back when I used to eat tofu, I tried it from whole foods and all kinds of places, but no matter what it had the bad effect). That said, I am not convinced soy does all that much for your health anyway, and I think they put soy in way too many processed foods (there is a laundry list I avoid because of that but I try to just avoid processed foods as much as possible), but I would bet all that sashimi I ate was a lot better for my healthy anyway.
A few years ago a health care practitioner put me on Soy protein. I turned on an allergy that was like Hay Fever from Hell. As soon as I quit the soy the allergy went away. The soy was good quality from a top brand non GMO etc.
As I mentioned my experience I found lots of people are similarly allergic to Soy. One person said it nearly killed Jay ( a mutual friend). I stayed totally clear of soy for many years and then I was taking supplements and got a skin rash and didn’t feel so good.
Checking the ingredients sure enough soy was there in small amounts in some of them. The supplements were all from reputable companies and non GMO.
On stopping taking the one’s containing soy again all allergies stopped.
The point I want to make is that a lot more people are allergic to soy than is commonly thought and the allergies can be quite severe.
It’s important to evaluate your source of evidence. Kaayla T. Daniel (a vocal critic of soy) received her “doctorate” from Union Institute and University, an online school that is not accredited by any recognized agency that grants a doctoral degree in two years. Ms. Daniel seems to be a pop nutritionist with no specific expertise in evaluating medical research. In contrast, Dr. Hyman is a practicing medical doctor, citing mainstream research published in well-known journals.
Dr. Hyman, this is my first time I am reading on this page.
And, I compleatly agreed with you 100% , that ” IT IS MORE IMPORTAN TO UNDERSTAND THE IMBALANCES IN YOUR BODY’S BASIC SYSTEMS AND TO RESTORE BALANCE, RATHER THAN NAME THE DESEASE AND MACH THE ILL”.
One of my concerns is who wants to do it?, when the medicine industry is big $!…
Thank you so much for your part in this world, educating us,
I wish, I could have a dr. with your mentalaty.
I enjoyed this article and appreciate your honesty and candor. You did not mention soy yogurt. Does it fall in the good or bad category?
Thank you for taking the time to present this over view of the issue. You have given us good food for thought, and just like every other food out there each person needs to decide is it for me. No two people are the same, so how soy affects me may be totally different from how it affect you.At least we have a few facts to look at.
It is not the soy that is bad , it is the processing that is bad, and that just goes back to your original advice, which is stay away from processed foods. Thank you again.
The Soy of Life skin cream ingredients linked to birth defects!
What research are you reading?? Were these studies sponsored by the soy industry? There is a lot of independent research that tells the oposite of what you are saying about soy. Perhaps you need to look at this matter again.
I started drinking soy milk for premenopausal symptoms in 1999. It clearly helped with those symptoms (as in they diminished when I was drinking it and returned when I lapsed in drinking it) and I grew to really like it. Six years later I started having allergic reactions to foods I have eaten my whole life with no problem, such as strawberries, almonds and cashews. I realized that adding soy milk was the only significant change I had made to my diet in those years. I eliminated all soy and nuts and strawberries for six months, then cautiously tried eating one nut at a time, mindful of reactions. Without soy in my diet, I again can eat all those favorite foods in moderation without any problem. I have no idea what the specific body-chemistry change was from the soy milk that initiated these other allergic reactions (hives on face and chest, swelling and tingling in lips, hands and feet) but my personal experience and experiment were enough to make my own decision not to drink soy milk anymore!
Tofu is not fermented, and I have not seen any fermented soy milk. I make my own tofu and soymilk as well as purchasing organic sprouted tofu. Please clarify why you said: . “For these reasons, I prefer fermented soy foods, like miso, natto, tempeh, tofu and some brands of soy milk.”
I am making keifer from my home made soy milk in an attempt to ferment the milk. Soymilk makers are great. I have fresh soy milk in 20 minutes from my sprouted organic beans.
I do not digest soy well at all, except for tempeh and other fermented soy products. I’ve tried soy yogurt, soy milk, soy ice cream, etc and I get horrid indigestion, bloating and crippling gas. So I avoid all soy products except for the fermented variety.
Dear Dr. Hyman.
First of all I would like to say Thank you for sending me lots of correct information in order to keep our life healthy in natural diet.I wish some one will translate your books in Urdu language.because English is not my mother Tungus.but I still get lots of knowledge from you.
With best regards,
jawed,Pakistan
I always aim at a balanced regime: 40% carbohydrates, 30% proteins, 30% lipids. I find it difficult to get the proteins at breakfast. Therefore I eat a mixture of old fashion oatmeal (carbo), lecithin (lipid) and two tablespoons of soya protein isolate (protein). I don’t realy want two eggs or two ounces of cheese with my cereals. I have done that for years. Should I stop the soya proteins isolates and replace it whith what?
Hi Angeline, thank you for your comment and for your interest in Dr. Hyman’s website. I think the message in this blog is about eating real, organic soy versus processed soy.
Wishing You the Best of Health!
Dr Hyman,
I also think you may have missed the boat on this one.
From what I understand, 3 bottles of soymilk formula may equal 1 birth control pill’s worth of estrogen.
Fermented soy (natto, miso) is what Asians are primarily eating, and relatively small amounts of tofu (unfermented).
About 80% of soy grown in the US has been genetically modified, and it is nearly impossible to find soymilk made with organic beans that did not come from China (organic?? pesticides? what does organic mean in China?).
The message should be to avoid all food additives and processed foods that contain soy derivatives, disguised under a lot of different technical names.
Hello doctor,
Can you recommend or tell me how to pick the healthiest brand of soy milk? I am in search of nom gmo milk and a minimally processed brand if possible.
After being asthmatic my entire life I switched from milk to soy milk, largely reducing my dairy intake and most of my asthma is generally gone as well as much less stomach bloating.
Thank you for your insight.
Melanie
Hi Melanie,
We like organic companies that have been third party tested for Quality Assurance for non GMO sourced soy as well natural fermentation instead of laboratory induced chemicals… A good example of this would be the brand Eden Soy. Check this article out for more info: http://www.non-gmoreport.com/articles/millenium/soymilkedenfoods.php
In good health!
Lizzy