By Leo Babauta

It’s one of those things that has spread on the Internet and unbelievably, has become accepted truth to many people: that soy is unhealthy, even dangerous.

I mention (to otherwise smart and informed people) that I drink soymilk sometimes, and a look of pity comes over their faces. ‘This guy doesn’t know the dangers of soy, and might get cancer, or worse … man boobs,’ they’re thinking.

Just about every fitness expert I read — people I respect and trust — says that soy is bad for you, from Tim Ferriss to the primal/paleo folk. I absolutely respect most of these guys and otherwise think their work on fitness-related matters is great. And yet, when I look for their sources on soy, often they don’t exist, and when they do, I can always trace them back to one place.

The Weston A. Price Foundation.

Seriously. I’ve never seen anyone cite a single peer-reviewed study that shows that soy is unhealthy. The only sources are the Weston A. Price Foundation, or other articles that use the Weston A. Price Foundation as a source (read more).

Here’s the thing: the Weston A. Price Foundation (WAPF) have been on a vendetta against soy (and on a campaign for meat and raw milk) for a couple decades now, and they have no solid evidence to back up their vendetta. They have lots of quasi-scientific evidence, lots of reasonable-sounding arguments, but if you look for solid proof, you won’t find any. They are not scientists, and have conducted no actual peer-reviewed studies of their own (that I know about).

It’s amazing how many people have been influenced by WAPF’s wacky writings — whenever you read articles not only against soy, but about the myths of cholesterol or saturated fat (WAPF dangerously advocates a diet high in saturated fat), or about raw milk or meat, or about coconut oil and butter … it is based on the work of WAPF. WAPF has even influenced the writings of major writers such as Gary Taubes and Michael Pollan.

I’m not going to tell you to fill your diet with soy. I eat it moderately, like anything else, but am not afraid of it. What I am going to do is clear up some myths, and challenge those who disagree with me to show actual peer-reviewed studies (not articles by WAPF or that cite WAPF as their source).

Who are the Weston A. Price Foundation?

I won’t do an entire treatise on WAPF, as others have done it better:

I’d encourage you to read these and consider the arguments and evidence, not the sources. While some of these articles are from vegetarians, that doesn’t negate the arguments — they just seem more motivated to do the research on WAPF than most people are.

But basically the WAPF is a fringe group that advocates some weird health claims about meat, raw milk, butter … but who came along just at the time when the meat and dairy industry was worried about soy being promoted as a healthy alternative. WAPF claims they don’t take money from agribusiness or the food processing industry, which is both true and admirable … but they do receive funding from sponsors and members — a large percentage of whom are dairy and meat farmers.

Anyway, the problem is not where their funding comes from — it’s their science. Sally Fallon (WAPF founder) and her co-author Mary Enig, WAPF board member Dr. Joe Mercola, Stephen Byrnes, and other WAPF authors use quack science to promote their agenda, and yet most people can’t distinguish between good and bad science. When they make claims about Eskimo diets being entirely meat and fat based, that sounds reasonable to most people, who don’t realize that you can’t just observe a people and make conclusions that are then generalized to other populations, or that the Inuit Greenlanders had the shortest life expectancy of any indigenous North Americans and high cancer rates (read more). Most people don’t understand how empirical science is done, and so don’t understand why criticism by the WAPF’s Chris Masterjohn of The China Study is a misinterpretation of the evidence.

Don’t take my word for it. Read the links above, become informed, weigh the evidence. Ask for the results of actual peer-reviewed studies, instead of relying on scientific-sounding arguments.

Does soy contain dangerous estrogens?

One of the most-repeated of WAPF’s myths about soy is that it contains dangerous estrogens that will cause cancer, man boobs, and a host of other health problems. So I thought it would be good to clear this up.

There is no evidence that eating soy causes any of the problems caused by raised levels of estrogen (a hormone that’s already naturally in our bodies).

The confusion that WAPF plays on is that soy contains a natural, non-steroidal compound called isoflavones, and also sometimes referred to as phytoestrogens — but actually many other plants and plant foods contain phytoestrogens too, including flaxseeds, sesame seeds, hummus, garlic, peanuts, and more.

Isoflavones are not estrogens, and though they might be similar, they have completely different effects on the human body. They do not affect the sperm count or concentration in men, nor do they affect the size of your testicles or volume of ejaculate (more). Note: A small-scale, preliminary study by Harvard researcher Jorge Chavarro found that processed soy might have some effect on sperm counts of obese men, but even Chavarro cautioned that nothing conclusive has been found (more).

Phytoestrogens don’t cause breast cancer in women (more).

Soy infant formula, while not nearly as good as human breast milk, is safe (more and more).

As you can see, I’ve linked to a few peer-reviewed studies that look at actual evidence, not pseudo-scientific arguments. There are many more that are easily found via Google. If you read or hear people making claims about soy and estrogen, ask for the sources, and ask that they be peer-reviewed studies.

Has soy been shown to be unhealthy?

In a word: no.

While I won’t claim that soy is a magic bullet for getting healthy, it also doesn’t have the dangers that WAPF and others claim it does. In fact, there is no evidence for any of those claims. I won’t get into all the claims, but just touch on a couple of the prevalent:

1. FALSE: Soy inhibits the digestion of nutrients (anti-nutrients). It’s true that soy, like many plants, have anti-nutrients — but when you cook, ferment, soak, roast, or sprout these plants, you do away with the anti-nutrients. From Dr. Andrew Weil: “There is no scientific data suggesting that soy consumption leads to mineral deficiency in humans.” (more) Fallon, Enig, and the other WAPF writers have failed to provide any evidence at all for this claim (more).

2. FALSE: Soy increases the risk of cancer. In fact, the evidence shows just the opposite. The Health Professionals Follow-up Study found a 70% reduction in prostate cancer for men who consume soy milk daily. The American Institute for Cancer Research, in collaboration with the World Cancer Research Fund, issued a major report in 1997 that analyzed more than 4,500 research studies, with more than 120 contributors and peer reviewers, including those from the World Health Organization, the Food and Agriculture Organization of the United Nations, the International Agency on Research in Cancer, and the U.S. National Cancer Institute. The report said that “Phytoestrogens are found in high concentrations in soya beans, and have been shown in vitro to exhibit a plethora of different anti-cancer effects, including inhibiting proliferation.” The report found some evidence that soy protects against stomach and prostate cancers. In 2000, Riva Bitrum, the President of Research for the American Institute for Cancer Research, said that “Studies showing consistently that just one serving a day of soyfoods contributes to a reduction in cancer risk are encouraging. Consuming one serving of soyfoods is a step most individuals would not find too difficult to take.” For healthy women, according to the American Institute for Cancer Research, “even two or three servings a day of soyfoods should be fine as one part of a mostly plant-based diet.” (more)

3. FALSE: Soy causes (insert scare claim here: Alzheimer’s, birth defects, etc.). There isn’t any evidence for any of the scare claims that originate from WAPF. I’m not going to argue them all, but I urge you to read these articles from John Robbins, Dr. Neal Barnard, Syd Baumel, and Dr. Joel Fuhrman — they contain many more sources than I could list here, and they’re based on actual evidence.

4. Legitimate concerns. Like most foods (meat, milk, peanuts, nuts, berries, chocolate, etc.), there are people with certain conditions that should be more careful. None of the legitimate concerns about soy are causes for alarm. Some people are allergic to soy. There is conflicting evidence about soy’s effect on women who already have breast cancer — some evidence suggests that it might be beneficial, but it’s not conclusive. If you already have a thyroid disorder, excess soy consumption (more than a couple times a day) could affect thyroid function (more). Again, none of these legitimate concerns is anything to be scared about — most people can eat soy a few times a day with no effects, according to the overwhelming mass of evidence, and even those who might have a concern can eat some amounts of soy with no problems.

So should I eat soy?

I honestly don’t care if you do or not. My general recommendation is to eat mostly real, whole foods — veggies, fruits, nuts, beans, seeds, a moderate amount of whole grains. I don’t eat meat or dairy for ethical reasons, but if you do eat meat, you should limit your intake of red meat (many studies have shown the health risks of red meat).

But soy has been eaten in moderation for centuries, and as I said above, has not been shown to be unhealthy. It can be included in a healthy diet — tofu, some soy milk, whole soy beans, tempeh can all be good for you if you mix them in with the other real foods I mentioned above. Soymilk is basically whole soy beans soaked in water and squeezed to produce a milky liquid, and tempeh is actual soybeans fermented.

I would be cautious about overly processed soy foods — processed soy protein — just as I would any other processed foods. Meaning, don’t be afraid of them, but don’t make them a major part of your diet. Eat real foods instead.

As a last note to doubters: I welcome your doubt — it’s important not to take my word as final. But instead of rebutting me with scientific-sounding arguments, show me the peer-reviewed studies. And not just one study, as no one study will be proof of anything — show me the mass of research that’s been done. When you look at the entirety of the research that has been done on soy, the evidence is overwhelmingly clear. I’d love to see someone show otherwise.

Update: As of 2016, I’ve now been eating soy multiple times a day for more than 9 years, and have not seen any health problems (no man boobs, no hormone problems) and am completely healthy. My diet includes a daily serving of soymilk (in my Ezekiel cereal with cinnamon and berries), and often tempeh or tofu twice a day, with lots of veggies.