Because my husband regularly consults for the soy industry, I’ve chosen not to write very much about soyfoods and health. And, since Jack published his excellent comprehensive article on the controversies surrounding this issue, there isn’t much need for me to do so anyway.
But two issues regarding soyfoods always prompt me to provide some clarification, because they seem to be universally—and consistently—misunderstood despite very clear and conclusive research findings. One pertains to the types and amounts of soy consumed in Asia which I wrote about several months ago. The other is the mistaken idea that soyfoods contain estrogen, which I want to address here.
Soyfoods are unique among commonly-consumed foods because they contain large amounts of isoflavones. And in order to understand the controversy around soyfoods, it’s necessary to understand what isoflavones are—and why they aren’t the same as estrogen. Sometimes referred to as phytoestrogens, isoflavones have a chemical structure that is very similar to the hormone estrogen, but small variations in their structure translate to important differences in physiological effects.
Both isoflavones and estrogen bind to and activate estrogen receptors (ERs) on cells. Human cells have two types of these receptors–ER-alpha and ER- beta—which have different distributions in different tissues. That doesn’t matter to estrogen, which happily binds to either type, but isoflavones are more finicky. They much prefer ER-beta. It’s an important distinction, because the two types of receptors produce different—sometimes completely opposite—effects.
As a result—while estrogen always acts like estrogen—isoflavones function differently in different tissues. They may have estrogen-like effects or anti-estrogenic effects, or no effects at all. For this reason, isoflavones are considered to be SERMs, or selective estrogen receptor modulators.(1)
Their selective nature makes some SERMs useful in medical therapy. For example, while estrogen therapy can protect bone health in postmenopausal women, it may also raise risk for breast cancer. In contrast, the osteoporosis drug raloxifene—which is a SERM—has estrogen-like effects on bones, but anti-estrogenic effects in breast tissue. So it helps protect bone without raising breast cancer risk.(2)
Because they function as SERMS, research is focused on potential health benefits of isoflavones, particularly as safe alternatives to estrogen. There is evidence that they may reduce menopausal symptoms like hot flashes,(3,4) but the findings on isoflavones and bone health are more conflicting.(5,6) And while some data suggests that isoflavone-rich soyfoods could improve prognosis in women who have breast cancer,(7-10) it’s not clear that women who begin consuming soy in adulthood will actually reduce their risk of cancer.
What we do know with certainty is that isoflavones are not estrogen and, looking at how estrogen acts in the body doesn’t tell us anything about the effects of eating soyfoods. In fact, if isoflavones were the same as estrogen, there wouldn’t really be any interest in studying them as alternatives to this hormone. The only way to know what isoflavones do is to study isoflavones
1. Oseni T, Patel R, Pyle J, Jordan VC. Selective estrogen receptor modulators and phytoestrogens. Planta Med 2008;74:1656-65.
2. Heringa M. Review on raloxifene: profile of a selective estrogen receptor modulator. Int J Clin Pharmacol Ther 2003;41:331-45.
3. Bolanos R, Del Castillo A, Francia J. Soy isoflavones versus placebo in the treatment of climacteric vasomotor symptoms: systematic review and meta-analysis. Menopause 2010;17:660-6.
4. Nelson HD, Vesco KK, Haney E, et al. Nonhormonal therapies for menopausal hot flashes: systematic review and meta-analysis. Jama 2006;295:2057-71.
5. Ma DF, Qin LQ, Wang PY, Katoh R. Soy isoflavone intake increases bone mineral density in the spine of menopausal women: meta-analysis of randomized controlled trials. Clin Nutr 2008;27:57-64.
6. Taku K, Melby MK, Takebayashi J, et al. Effect of soy isoflavone extract supplements on bone mineral density in menopausal women: meta-analysis of randomized controlled trials. Asia Pac J Clin Nutr 2010;19:33-42.
7. Shu XO, Zheng Y, Cai H, et al. Soy food intake and breast cancer survival. JAMA 2009;302:2437-43.
8. Guha N, Kwan ML, Quesenberry CP, Jr., Weltzien EK, Castillo AL, Caan BJ. Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study. Breast Cancer Res Treat 2009;118:395-405.
9. Caan BJ, Natarajan L, Parker B, et al. Soy food consumption and breast cancer prognosis. Cancer Epidemiol Biomarkers Prev 2011;20:854-8.
10. Kang X, Zhang Q, Wang S, Huang X, Jin S. Effect of soy isoflavones on breast cancer recurrence and death for patients receiving adjuvant endocrine therapy. Cmaj 2010;182:1857-62
[…] well worth reading for anyone wanting a better understanding of where soy bashers lose the plot. Link. Spread the […]
Another awesome article! It always blows my mind when I get into discussions with WAPF/Real Milk types, and they get all preachy about soy and estrogen and oh the babies! I can’t help but think of
a) the many, many other foods that contain phytoestrogens (flax, almonds, etc) that they choose to ignore because it’s not en vogue to demonize those foods, and
b) um, forget pretend plant estrogens, what about the *dozens* of REAL, ACTUAL mammalian hormones that are naturally present in all dairy foods??
Crazines, I say.
Thanks for a clear explanation!
At times, I wonder how someone can look at themselves in the mirror in the morning.
If estrogen is so different from soy isoflavones why did this guy’s estrogen levels go up when he was drinking a lot of soy milk and down when he stopped all soy consumption?
http://www.menshealth.com/nutrition/soys-negative-effects
Why has the American Academy of Pediatrics recommended milk based formula for infants who can’t be breast fed instead of soy formula?
Why did men who consume half a serving a day of soy have about 40% lower sperm count than men who consume no soy?
http://www.newscientist.com/article/dn12792-eating-soya-could-slash-mens-sperm-count.html
The first article focuses on the case of one guy — this is not a study of hundreds or thousands of people. The second article begins, “Men who eat just half a serving of soya a day have drastically fewer sperm than those who do not consume such foods, according to a small, preliminary study.” Keywords, “small, preliminary study.” If you delve into the peer-reviewed literature and look for large, high-quality studies, systematic reviews, and meta-analyses, the picture becomes a lot more murky. I looked around and found everything I could that fit that description, and did not come away with a very alarmist position.
The American Academy of Pediatrics position on soy-based formulas is not as alarming as you imply: “In summary, although studied by numerous investigators in various species, there is no conclusive evidence from animal, adult human, or infant populations that dietary soy isoflavones may adversely affect human development, reproduction, or endocrine function.”
Thanks, Anna, for sharing some perspective on this.
Daisy, in the case study reported in Men’s Health, the subject was consuming nearly 10 times the amount of soyfoods in a typical Japanese diet. There are any number of healthy foods that would cause problems at those high intakes. In contrast to that, the actual clinical studies show that even when men consume as many as 6 servings of soyfoods per day–which is still much higher than usual Asian intake and higher than recommended amounts of soy–they don’t experience feminizing effects.
In the study on sperm concentrations, the concentrations were lower because volume of ejaculate was higher. So actual sperm volume wasn’t lower. And the dietary questionnaire used in the study hadn’t been validated, which makes it very difficult to get a picture of overall diet. That’s important, because many dietary factors affect sperm count.
Finally, the American Academy of Pediatrics does in fact consider soy to be a safe alternative for infants.
You can continually make excuses if you want, Ginny. But IMO, it’s dishonest and dangerous for someone with your influence to continue to say soy is safe with absolutely no restrictions!
Yes, the MensHealth article was only one man. And he drank a lot of soy milk. Why? Because the soy industry has spent $billions (including supporting you and your husband very well) in pormoting the idea that soy is a healthy, safe food, that it cures cancer, menopause, and a multitude of other diseases. In your original post on this thread, you specifically said “…isoflavones are—and why they aren’t the same as estrogen.” While they are not estrogen, it’s obvious from this man’s sad experience, they do affect estrogen levels…in men, likely in women and children. I believe you know that and still encourage the consumption of this potentially dangerous food!
Yes, there’s an impressive list of “research” supporting your article. I’d wonder how many of those studies were done while “Dr. Soy” was handing out grants at the NIH? Before he went to work directly for the soy industry? Do you have a count? The dates aren’t in your reference or it would be quite easy to find out.
And, yes, the AAP still recommends soy formula….as a last resort. Breast milk is their first recommendation, cows milk next, then soy.
http://aappolicy.aappublications.org/cgi/content/full/pediatrics%3B101/1/148
Daisy, in the interest of fairness, would you be willing to share what you do for a living? From your email address, I’m wondering if it might have something to do with the cattle industry.
My husband left the National Cancer Institute in 1992, and as far as I know, none of the studies referenced in this post were the result of his ability to “hand out grants.” He worked for the Diet and Cancer branch of the NCI, and his job was to identify areas of potential research for dietary prevention of cancer. For various reasons related to the state of the science at that time, his focus was on a possible relationship of soy to breast cancer. His perspective on issues related to soy is actually very balanced, and when the research doesn’t support a benefit for soyfoods, he’s always willing to say so. That’s one reason why he is well respected within the scientific community as an expert on issues related to soyfoods. It’s certainly your right to question his integrity but I think you’d find that most people in the nutrition field who know him would disagree with you.
Soy has been a part of Asian diets for at least 2,000 years, so it’s hard to imagine that it’s a “dangerous” food. Furthermore, many compounds that are perfectly benign—or even beneficial—in usual quantities can be harmful in high doses. For example, high intakes of vitamins A and D are toxic. Would you say that this makes foods that contain these vitamins “dangerous?”
Several months ago a case study reported in the New England Journal of Medicine referenced a woman who nearly died from eating large amounts of bok choy because of the effects of glucosinolates which are found in cruciferous vegetables. These are the same compounds that are believed to have anti-cancer activity. Would you say that cruciferous vegetables (cabbage, kale, Brussels sprouts, etc) are dangerous foods?
Plant foods contain chemicals—such as isoflavones—that have biological activity. How these chemicals act when people consume megadoses of them has nothing to do with their safety at usual levels of intake. I don’t know anyone who thinks it’s a good idea to eat 15 servings per day of soyfoods. Or 15 servings of vitamin A-rich liver or 15 servings of bok choy.
Fairness? My husband is in the military. I don’t work outside the home or draw a paycheck for any work.
Attacking the messenger won’t change the facts, Ginny. The articles are the articles. The research is the research. And there’s much more of it out there damning soy. I put these out there because of your blatant assurances to your readers that the isoflavones are not a danger to health. They certainly could be and have been to some people.
The Bok Choy industry doesn’t spend $billions every year promoting the health benefits of their product. The soy industry does. I doubt the Bok Choy industry gets $billions in farm subsidies every year from the US government. The soy industry does. I doubt the Bok Choy industry has a “Dr Choy” handing out research grant money at the NIH either.
In the 2,000 years of human consumption, soy was not eaten like it is today…either the quantity or kind. Today you don’t have to buy soy to eat it. You get in bread, cooking oils, cereals, and a multitude of other places without realizing it. You know that, yet you continue to use your VEGANRD credentials to promote it without any restrictions or warnings. Shame on you.
But then when religion and money comes together, bad things can happen….often to other people.
“You get in bread, cooking oils, cereals, and a multitude of other places without realizing it.”
Plus a lot of other undesirable stuff. Which is yet another reason why I don’t eat “food” that comes from a box. Unprocessed whole foods is the way to go. I shop the outer isles of the grocery stores and the farmer’s markets.
Daisy. I’m sure you can understand why your email address suggested a possible relationship to the beef industry. I apologize, though, if my question read like an “attack.” I was only trying to get some clarification about your interest in this topic.
The fact that soy is present in a lot of foods has nothing to do with your argument about the safety of isoflavones. The food industry uses isolated soy protein—which typically contains only very low levels of isoflavones, if any at all—as a functional ingredient. It’s there in small quantities and has little nutrition relevance. So yes, there are small amounts of soy in many, many foods. For the most part, they don’t contribute isoflavones. And I don’t think you see me promoting those types of mainstream processed foods, most of which aren’t vegan.
I think you’d be surprised at how little money is spent on promoting soy for human consumption—an amount that is dwarfed by that spent in promoting animal foods. You might be confusing this with money that is spent on support of soybean farming for other purposes. I’m sure you’re aware of the fact that the vast amount of soy grown is this country and in South America is for animal feed and soy oil. (Have you ever heard me promote use of soy oil?) And the NIH does, in fact, fund research on cruciferous vegetables and has done so for many years. Along with berries, fish oil, grapes and many other foods.
You are insisting that soy is dangerous because someone suffered negative consequences from eating ridiculously large amounts of it. I was merely pointing out that this is an argument that doesn’t make sense. Many, many foods are dangerous in large amounts; it doesn’t mean that it isn’t safe to consume a few servings a day of these foods as a regular part of a varied diet.
The research is the research, but the majority of it is certainly not damning soy. What are you reading? Articles from magazines or the actual research published in peer-reviewed journals? If you refined your search to high-quality articles published in peer-reviewed journals, a much less scary picture would emerge. The evidence just isn’t there that the isoflavones in soy will mess up your endocrine system. Strip away all the politics, and it’s just a food. It’s not poisonous and it’s not magical either. But it is versatile and full of protein, which is why I eat it.
I would only add that if you don’t like soy (I won’t touch it) then don’t eat it. Simple! There are plenty of other foods one can add to a vegan diet.
Just a brief word on peer-review – its not the be all and end all you (and I) may have thought it was.
http://oncampus.macleans.ca/education/2011/01/06/the-problem-with-science/
No wonder I’m becoming more skeptical as time goes on! :o(
“In the 2,000 years of human consumption, soy was not eaten like it is today…either the quantity or kind.”
I guess you have not spent much time in south east asia, korea, the phillipines, japan or china. Soy foods have been around for more than 2000 years!
I am an Asian living in Hong Kong. I can assure you that my ancestors have eaten much higher quantities of soy in all its various forms than what you would ever do in the west because meat was not easily affordable in the past and soy was a nutritious, cheap source of protein! It certainly has not affected our ability to reproduce and flourish since we are today one of the most populous peoples in the world!!
Well said! 🙂
@Daisy:
Your post reads like a prototype for confirmation bias.
To me, it looks more like a prototype for trolling.
We don’t need soy milk, and we certainly don’t need cow’s milk. It’s a beverage. If I need to use a little bit in a recipe, I would much rather use soy, rice, or almond milk….never cow’s.
I didn’t understand the article. Is soy dangerous or not? Does it promote breast cancer or decrease the risk?
Veroni, the article was really just meant to point out that isoflavones are not the same as estrogen, and didn’t got into issues of safety and benefit, so I understand your confusion.
Basically, eating soy the way that Asians do–1-3 servings per day of traditional foods–isn’t associated with harm. The exceptions are people with soy allergies, of course, and also possibly people who have sub-clinical thyroid disease and are not taking medication.
As for breast cancer, soy appears to be safe, but it’s not really known whether it’s actually protective. There is some evidence that girls who eat soyfoods in puberty have a lower risk for breast cancer later in life. And also new evidence to suggest that in women who have had breast cancer, eating soyfoods may lower their risk of recurrence. But these are epidemiological studies so they aren’t definitive, and we just don’t know whether soy is protective or not. But at the very least, it appears to be safe.
I’m taking Soy Isoflavones tablets to treat hot flashes and night sweats. It did worked like magic for the first month of usage but I’m having the ‘heat” attacks again lately although not as bad when it all started early this year. I will continue taking it, especially knowing that it is safe. My question is, what is the maximum intake of these tablets per day, at 50mg/tablet?
I try not to do soy as much as possible..But not cause I’m paranoid of it and it’s health pro’s and con’s… However I will never do cows milk ever again.
Almond milk seems to be my love…I’ll just stick with it 🙂
[…] Soy Isoflavones and Estrogen But two issues regarding soyfoods always prompt me to provide some clarification, because they seem to be universally—and consistently—misunderstood despite very clear and conclusive research findings. One pertains to the types and amounts of soy consumed in Asia which I wrote about several months ago. The other is the mistaken idea that soyfoods contain estrogen, which I want to address here. […]
I would like to add that many folks, including many vegans, are low/deficient in iodine, which can lead to thyroid issues. I’m recovering from an iodine deficiency at the moment, and soy does affect me (sending my TSH high, as well as other symptoms). People in Asia generally eat a much more iodine rich diet than in other parts of the world. Since many vegans may use sea salt instead of iodized table salt, the problem may be more of an iodine issue than a soy issue per se. Also, because the thyroid is so sensitive to iodine, it’s important to get the ‘right’ amount, i.e. not too much and not too little. For example, eating too much seaweed/kelp/nori/dulse can also cause problems, and the amount of iodine in seaweed can vary greatly. This could technically cause issues for people trying to heal their thyroid problems. For me, I have to supplement, so that there is a specific controlled amount going in every day, and not a lot of crazy variance. But I am healing from a deficiency, so my situation is a bit more picky.
Ginny,
I congratulate you on your patient, factual and well-balanced responses to the comments by Daisy, despite her quite unwarranted insinuations that you are hiding information about soy’s dangers. We have to be guided by the research when it comes to the safety or otherwise of food, and you have shown in your blog and books that you are open minded enough to report the research accurately. The chapter on soy in your Dietician’s guide to Vegetarian Diets is one of the best overviews of this controversial topic that I have read.
Keep up with the good work – it is much appreciated.
Regarding breast cancer, have there ever been done any long-term studies which show a possible link between a specific diet and breast cancer? For example, does breast cancer occur more in women who eat meat compared to those who are vegetarian?
[…] does contain isoflavones (also called phytoestrogens), which have a structure similar to estrogen’s but not similar […]
[…] Soy does contain isoflavones (also called phytoestrogens), which have a structure similar to estrogen’s but not similar enough for them to have equal effects in our bodies. Isoflavones exhibit different effects in different tissues; they might have an estrogen-like effect, anti-estrogen effect, or no effect at all. There have not been any comprehensive studies on isoflavones’ effects but you can bet there is currently a ton of research underway. Given soy’s plant origin and combined cholesterol and blood pressure-lowering properties, I am willing to bet it’s in the clear. […]
[…] is of interest to you to spend some time reading about it, a good place to start might be here: http://www.theveganrd.com/2011/0…. Read the linked page first to understand who the information is coming from, but the real […]
[…] Not wanting to take things like this at face value, I wanted to learn more. I dove into some online research to discover that soy is an isoflavone. Isoflavones have a similar chemical structure to the hormone estrogen. Isoflavones are not a substitute for estrogen, as they are ‘selective’ in how they work. I found a comprehensive article, written by Ginny Kisch Messina, MPH, RD, who used reliable references, to offer a very good, easy to understand explanation of how the soy isoflavone works in the body. If you are interested in reading more, go to http://www.theveganrd.com/2011/08/soy-isoflavones-and-estrogen.html. […]
Ginny, sorry to bring up an old topic, but could you explain something to me?
Why is soy singled out in this estrogen “scandal”? Is there a difference between soy isoflavones and others? I mean, don’t all legumes and bean sprouts contain isoflavones? Why aren’t people flipping out about eating chickpeas, peanuts, or alfalfa sprouts?
[…] Caution: there are a lot of alternatives that are soy-based on the market today. Soy presents a major concern because it is considered one of the TOP GMO’s being produced today. Not only is soy suspect for being a GMO, but high consumption of soy can be detrimental to women’s health because it may increase estrogen in the body. Increased estrogen may lead to increased risk of breast & reproductive cancers. However another source cites that soy is actually a “selective estrogen receptor modulator” or SERM. Read more on that here from the Vegan R.D. […]
Thanks so much. You have presented it excellently. I will forward this information to a family who maintains that soy elevates estrogen levels – and that because so many babies have been put on soy formula, we are seeing many more people leading “alternative lifestyles”. That’s akin to saying that if a food is labeled “Kosher” or “Parve” the Jewish community gets a cut of the profits. I heard that one quite a few years back. Such a lack of knowledge, and in many cases an unwillingness to learn.
I definitely learned much from your article and the blogs.
[…] a website The Vegan RD the women writer talks about the misconception that soy based products contain estrogen, when in […]
Hi Ginny;
I am an experiment of one. I am 50 years old, going through terrible menopausal symptoms. I have been suffering for at least 5 years. I am on HRT. However, my cognitive ability had been declining so quickly, I thought I was getting Alzheimer’s. Anyway, being of Asian descent, I decided I would try adding a soy supplement to my diet. Not only did it reverse my precarious cognitive decline, it made my mood so much lighter. I am much more gregarious and I have found my sense of humour again. I’d really missed my sense of humour, which had gone to the wayside with menopause.
I am not trying to convince anyone of the benefits of soy. I am simply offering my experience. I am an educator, so my mind is my living.
Soy has literally saved my cognitive ability from dissolving.
Hi, just wanted to say, I loved this post. It was helpful. Keep on posting!
Hi – I recently found out that I have at least 30 fibroids in my uterus and am scheduled for a hysterectomy in September. Now I can try to shrink them by taking a hormone drug that I am opposed to or I was going to try and eliminate soy from my diet to see if that can shrink them. I am a complete newbie when it comes to being vegetarian. In fact, I have only been following a vegetarian/sometimes vegan diet since last August.
I read in another article that soy can prevent fibroids from ever forming but what about shrinking the ones you already have? Any advice/comments/suggestions will be greatly appreciated!!! I am willing to do anything at this point to shrink these things.
It appears as though Ginny isn’t keeping up with this now, or maybe she doesn’t know it’s been a refreshed topic on Facebook yet…
I have recently gone Vegetarian, I have a family of 5, we’re still doing dairy and eggs because I’m afraid, from a nourishment standpoint.
What I’ve been reading is that SOY isn’t actually digested beneficially UNLESS it’s FERMENTED — Natto, ew.
So, I do wonder what to talk about in all this…
Also, PHYTIC acid in legumes is not particularly wonderful to ingest, beans, grains, etc. should all be soaked to release the nutrients we need.
Needless to say, I am SO completely overwhelmed and confused.
I’d LOVE some REAL information. 🙂
Jamie, soy is actually well digested from foods like tofu and soymilk as well as from fermented foods like tempeh and miso. All beans and whole grains contain phytic acid which does interfere to some extent with mineral absorption. However, because they are so high in iron, you end up absorbing some. In fact, iron is very well absorbed from soyfoods, even the unfermented ones. And you can increase the amount you absorb by eating a vitamin C-rich food with the grains or beans.
[…] more information on soy, please see Virginia Messina’s article “Soy Isoflavones and Estrogen.” For a well-researched contextualization of carrageenan with citations, please see “Is […]
I can second what Susan says about the ability of isoflavones to help with menopause symptoms. I eat as much soy and drink as much soy milk as I comfortably can. In reality, this works out to an average of 1-2 servings a day. In addition, I take red clover supplements (another source of isoflavones). This has dramatically reduced the frequency and intensity of hot flashes. I’m hoping I will also get the cognitive lift that Susan describes!
anyone care to comment about the supposed high levels of Enzyme inhibitors present in non-fermented soy products, and the claimed negative effect it may have on digestion and interference with the body’s natural enzymes?
[…] Society on Soy: here, Jack Norris, RD “Soy: What’s the Harm?” , Ginny Messina, R.D. “Soy Isoflavones and Estrogen”, Academy of Nutrition and Dietetics on Soy Safety, More on Soy from the American Institute for […]
[…] tief auf die biochemischen Zusammenhänge einzugehen (wer sich dafür interessiert kann dies gern hier nachholen), kann man festhalten: Phytoöstrogene können östrogenähnliche, anti-östrogene oder auch […]
[…] • Soy Isoflavones and Estrogen […]
Is there any documented evidence that women with endometriosis should avoid eating soy? I’ve read recommendations for both avoiding soy and including soy in the diet of women with this condition.
Thank you.
[…] http://www.theveganrd.com/2011/08/soy-isoflavones-and-estrogen.html […]