"Eating soy will 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.
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.
Mark Hyman, M.D. is a practicing physician, founder of The UltraWellness Center, a four-time New York Times bestselling author, and an international leader in the field of Functional Medicine. You can follow him on Twitter, connect with him on LinkedIn, watch his videos on YouTube, become a fan on Facebook, and subscribe to his newsletter.
Follow Mark Hyman, MD on Twitter: www.twitter.com/markhymanmd
http://en.wikipedia.org/wiki/Phytic_acid
http://en.wikipedia.org/wiki/Trypsin_inhibitor
http://en.wikipedia.org/wiki/Soy_protein
Hyman misrepresents soy research. Long having advised eating soy, he perceives the research through a cloud of bias favoring his advice.
If a soy product is not both (a) 100% organic & (b) fermented, it is DANGEROUS.
Hyman’s assertions are misleading. Here are five (of many) examples:
(1) Hyman asserts: “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.” That assertion is false.
(2) Hyman asserts: “All population studies (...of people) of soy either show reduced breast cancer risk or no effect.” That assertion is (a) partly false (his term “All”) and (b) very misleading, since it does not account other cancers or for the matter that soy affects males and females and old and young differently and does not account for reliable animal-studies.
(3) Hyman misrepresents the soy-eating of the Okinawan population, which eats mostly fermented soy — very little or no non-fermented soy.
(4) Hyman cites Messina, A brief historical overview of the past two decades of soy and isoflavone research. But Messina says, among else: “...in vitro and animal research has raised questions about the safety of isoflavone exposure..., although the human data are largely inconsistent with these concerns.” Note: the term “largely inconsistent” does not equal “contradict,” and enough studies SUPPORT “these concerns.”
CONTINUED with PART TWO
(5) Hyman cites Persky, et al, Effect of soy protein on endogenous hormones in postmenopausal women. But that piece concludes: “This study does not provide evidence that long-term ingestion of soy protein alters steroid hormone values, but it suggests that soy protein may have small effects on thyroid hormone.... The thyroid effects are...consistent with previous findings in animals and highlight the need for future research investigating possible mechanisms of action.” And note: the study covered only soy PROTEIN and POSTMENOPAUSAL WOMEN.
NON-FERMENTED soy's phytic acid blocks mineral absorption. Its trypsin-inhibitors impair nutrition. Its hemagglutinin causes pathological blood-cell agglutination.
NON-FERMENTED soy’s isoflavones may cause thyroid & thymic abnormalities, sexual/reproductive ills, digestive-system distress, immune-system dysfunction or degeneration, cognitive decline, cardiovascular disease, and some cancers.
Non-fermented soy is allergenic in many humans. If not 100% organic, it is toxic because of MASSIVE doses of pesticides, herbicides, and toxic fertilizers; and near-all is genetically engineered, hence MORE toxic & allergenic.
The matter is not that non-fermented soy will harm everyone who eats it. The matter is that non-fermented-soy threatens health SUBSTANTIALLY.
See these references AND THEIR references.
http://thyroid-info.com/articles/soydangers.htm
http://personalhealthzone.com/vitamins_supplements/soy_side_effects.html
http://current.com/14mbu4c
http://seedsofdeception.com/utility/showArticle/?objectID=296
Beware of soy-industry/genetic-engineering-industry propaganda like
http://en.wikipedia.org/wiki/Soybean
according to Kazuhiko Taira - 12% are "flavonoid-rich" foods, not just soy. Okinawans eat 100 grams EACH of pork and fish each day. Legume consumption is around 75 grams per day, from all legumes, soy included. Many other studies like China Study found around 12 g per day total legum consumption, a third of which is soy. And let us not forget the devil in the details, they're not eating extruded solvented product usually. As someone who has seen the symptoms from years of soy eating in my body and my family, I can definitely say getting off soy has been a major improvement for me personally.
Why's a nice guy like him doing in a place like this?
Soy plays a necessary role in too many people's "-ism" to be condemned. As one of the few plants with a decent enough amino profile to be considered a complete protein, if you're coming from a vegetarian or especially vegan first principle, then you "need" soy to be good, soy "must" be good, because if it turns out one of the only plants that can meet our protein needs is otherwise toxic-junk, then your entire "-ism" falls apart. Particularly if you're advocating it for health reasons.
"Scientists at the Shanghai Cancer Institute found similar results when they studied the relationship between soy intake and breast cancer rates. The Shanghai Women's Health Study, published last year, showed the more soy protein women ate in a day, the less likely they were to be diagnosed with breast cancer. Farquhar recommends daily helpings of 8-10 grams of soy protein, which can be found in tofu, soy nuts, soy milk or edamame.
According to the Centers for Disease Control, breast cancer is the most common cancer for women in the United States, followed by lung and colorectal cancers. The list is the same for men, except that prostate cancer replaces breast cancer at the top of the list. According to Farquhar, a strategic, healthy diet can help prevent these cancers.
He recommends a daily serving of berries, especially blueberries, which deliver a high concentration of antioxidants that help prevent cell damage that occurs naturally with age. Slowing age-related cell damage helps prevents cancer and other diseases".
So far, 12 generations of cattle have thrived on GM soy and corn. There have been absolutely no signs of any negative effects. Nutritionally, GM is identical to non GM. Many, many tests and studies confirm this.
It's helpful to ask yourself why virtually all scientists and nutritionists say that soy is soy and corn is corn, with no significant difference between GM and conventional.
Lots of folks blame that on a conspiracy between government, industry, academia, and the target du jour. Me, I believe the experts all all saying same thing because it's true.
Mindless shill accusations begin in three, two, one . . .
You state that 12 generations of cattle have thrived on GM soy and corn. Then why are antibiotics in greater use today in cattle than ever in history? If one simply evaluates the lay information available it is clear that there are significant illnesses inherent in cattle today. Well more than 50 years ago. It is incorrect to state that "studies" confirm nutritional equivalence. This is simply not true. Nutritional equivalence is not maintained and is in fact a roll of the dice. The methods used to modify food to GM status is not controlled and is in fact risky at best. There are however significant studies that identify nutritional deficiencies in GM food.
When the GM food industry presents their " study" findings for peer review to financially non-aligned scientific groups and makes their study design and data publicly available we can get much closer to the truth. Meanwhile, GMO is a health crap-shoot and certainly not worth the health risks posed.
They are legal here because our US government is heavily lobbied by multinational corporations who actually write laws that are then introduced by heavily funded congressmen. These corporations care nothing about you or your health, only that they create the highest possible profits for the cheapest possible food to produce.
Look at what happened to the American ag corporations that found themselves in competition with Monsanto and DuPont. Does anyone seriously think that European ag corporations want to endure that kind of competition? The only way for them to survive is to persuade their politicians to pass protectionist laws that pretend to protect consumers.
I find it amazing that so many people think that the European Union decided to block American biotech competition because a bunch of English housewives are afraid of "Frankenfood."
I mean, billions of Euros are at stake. How can anyone be so naive?
Obviously, we should all pay attention. After all, they wouldn't print it if it wasn't true.
You don't have to pay attention to anything at all. That is your business.
My comment was for those individuals who choose to gain broader knowledge on this subject and who have personally developed ailments from the consumption of soy.
You choose to be in the dark that is your problem.
Screw the FDA and Monsanto. Screw Obama for appointing another Monsanto man in the FDA.
I am growing black soybeans right now, and boy, do they have a richer, more delicious flavor. Next harvest I am going to make tofu with these black beans and see what it comes out like.
Plus, if you want to hold out China as some sort of example for natural, unprocessed, unadulterated food, you might want to reconsider...
I cook with soy milk, you have to get the unsweetened brand, which is what I buy.
cereals, pancakes, mashed potatoes everything tastes so much better and smoother.
Every new crop variety has the potential to contaminate previous varieties. This was as true 100 years ago as it was today. Contamination is never a good thing, but non-GMO contamination is actually worse.
We never had STAR-LINK corn episodes with hybridized Maize....