Is Soy Really Bad for Us?

Monday Mar 6 | BY |
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fresh tofu on table

Let’s have a debate about soy!


“You mean, you’re doubting the fact that soy is a horrible so-called “health” food that causes vegetarians to get sick and men to become effeminate from all the hormones it contains?” I already hear some of you say.

I don’t think there’s as much debate about any natural food as there is about soy.

Maybe it’s because tofu is associated with vegetarian diets and hippies; anyone wanting to criticize those diets chooses soy as their main enemy. Maybe it’s because some soy products have flooded the natural food market in such quantities that they’ve snuck into too many food products.

The real question is: is soy good for us or bad for us?

If you read any Paleo blog, soy is definitely one of the enemies. It gall goes back to an article that was published in Mother Jones that blamed soy for causing a number of health problems.

Soybeans are very particular compared to other beans because they contain phytoestrogens, which is a plant clone, so to speak, of our body’s natural estrogen hormones. These so-called phytoestrogen had been linked to some health problems such as low testosterone in men, low sperm count, increased risks of cancer, and infertility. These phytoestrogens are often classified as endocrine destructors. These are chemicals that interfere with the normal function of the hormones in the body.

In an article by Wellness Mama, “These phytoestrogens are so strong that a baby consuming only soy formula is consuming the equivalent hormones of four birth control pills a day.” Of course, there is no reference for that quote, but we’ll see some scientific evidence to show what these phytoestrogens can do.

One common attack on soy and beans in general, is the phytic acid that it contains. Another common complaint is thyroid health. Soy contains goitrogens, which are classified as antithyroid compounds, which can lead to thyroid problems.

When you look at the literature about soy, it’s very confusing because we have many contradicting studies:

  • In 1986, a two-year diet of soy for rats caused enlarged pancreas.
  • A 1989 study showed that soy products have no adverse effects on the human pancreas.
  • In 1991, a study was published showing that soy foods have a potential role in cancer prevention.
  • In 1994, another study was published dictating that soy diets may offer protection against breast, colon and prostate cancer. Also in 1994, Japanese and Chinese women were found to have low incidence of breast cancer because of high consumption of soy.
  • In 1995, another study showed that soy cannot be considered a factor in the low incidence of breast cancer among Japanese and Chinese women. A 1995 study also showed that soy inhibits growth of various tumors in rats.
  • A 1996 study showed that soy-based diets do, indeed, offer protection against breast cancer among Asians.
  • In 1997, a study showed that soy foods might reduce the risk of premenopausal breast cancer. That same year, the consumption of soy food was found to possibly decreased risk of prostate cancer.
  • In 2000, a study showed that soybean foods may prevent urinary track cancer.
  • In 2003, the consumption of soy foods was found to reduce the risk of prostate cancer. The same year, soy supplements were found to have minimal effect on prostate-specific antigen levels of prostate patients.
  • In 2004, consuming soy in green tea was thought to limit the progression of breast cancer.
  • In 2005, soy protein was thought to protect against cancer. That same year, soybean paste and kimchi were considered risk factors for gastric cancer.

As we can see, in terms of cancer, while the vast majority of studies show positive affects, we do not come across any studies that conclusively show that soy foods contribute to cancer. In fact, most studies done after 2005 show that soy foods are associated with lower cancer risk.

In 2009, a study showed that among women with breast cancer, soy food consumption was significantly associated with a reduced risk of death and recurrence. Another study showed that early soy food intake, for example, reduced breast cancer risk. In 2010, a study showed that the consumption of soy may reduce risk of colon cancer in women, but not in men. In 2012, a study showed that soy foods may reduce the risk of lung cancers in non-smoking women.

Now, when it comes to cholesterol, all the studies show that soy food consumption lowers bad cholesterol and increases good cholesterol, and reduces the risk of heart disease.

When it comes to these phytoestrogens and their affects, in 1995 a study showed that soy has no estrogenic affects on postmenopausal women. However, in 1998, a study showed that soy protein supplements substantially reduced the frequency of hot flashes in postmenopausal women. This was contradicted by a study in 2001 that showed soy protein does not reduce menopausal symptoms. In the same year, another study showed that soy products do have a protective effect against hot flashes.

When it comes to men, there is a meta-analysis published in fertility and sterility, based on fifty treatment groups that showed that neither soy products nor isoflavones supplements from soy affect testosterone levels in men. Some studies show that soy products reduce prostate cancer risk in men.

As for genetically modified soy, some studies show that there is reason to be concerned, and most studies show that there is no problem with the genetic modification of soy.

In terms of health and longevity in general, a 1988 study showed that a soy diet increases longevity. However, in 2005, a study showed that soy products should be limited in young children and consumption can lead to higher risk of cancer, male infertility, and may affect human hormones; this was published in the British Medical Journal.

This is just to show you how confusing the data is!

The Bottom Line & Arguments Against Soy

I would say that from reviewing those studies, soy shows promise and the vast majority of research shows positive affects.

We hear that soy contains anti-nutrients that interfere with the digestion of protein and the absorption of minerals, but this would be a problem if soy products were consumed raw, which is never the case.

For cancer, the vast majority of studies show positive affects on cancer; breast and prostate cancer rates are four to six times lower in Japan and China than in Western countries where little soy is consumed.

When it comes to sex hormones, some studies show problems. However, if we look again at soy-consuming countries, they not only have no problems making babies, but also have fewer hip problems, hot flashes and postmenopausal symptoms in women. In terms of thyroid issues, the problem may actually come more from iodine deficiency than soy consumption. Some studies show that soy isoflavones and soy isolates may suppress the immune system and reduce the size of the thymus gland. Overall, there are also other studies showing that soy actually improves the immune response.

After spending a few days reviewing the medical literature, I came to a pretty simple conclusion.

In reasonable quantities, traditional soy products are healthy. Refined soy products, while often being better than the meat products they replace, are best avoided. 

The way soy is consumed in the West is usually in the form of tofu, soy milk but more importantly soy isolates (textured soy protein that is used in protein bars, fake meats); they’re used by the food industry to replace other types of protein.

In Asian countries, people consume fermented soy products (such as tempeh and miso), as well as whole soy beans, also called edamame. They also consume tofu (which is made from soy milk). What’s important to understand is that soy foods are a part of the Asian diet, but they’re used more as a condiment. Roughly 5% of daily calories in a typical Japanese or Chinese diet may come from soybeans; that’s about 2 ounces of soy food or about 60g a day, which is not a huge amount. Here’s two ounces of tofu:


So, could it be that the vegetarians eating soy in America are a little over-doing it?

The Paleo blogging community has decided to attack soy viciously, and they have some reasons to do so. However, if we look at the evidence, if we look at the health of Asian nations compared to Western nations, and if we look at soy consumption in Asian countries, we can come to our own conclusions.

Personally, I do enjoy some soy products. I don’t consume huge amounts of it, but I do like to put little cubes of tofu in my salad, and consume other soy products, such as tempeh. I’ve never experienced any problems with this type of soy consumption — only benefits.

Please leave your thoughts below.

Frederic Patenaude

Frederic Patenaude has been an important influence in the raw food and natural health movement since he started writing and publishing in 1998, first by being the editor of Just Eat an Apple magazine. He is the author of over 20 books, including The Raw Secrets, the Sunfood Cuisine and Raw Food Controversies. Since 2013 he’s been the Editor-in-Chief of Renegade Health.

Frederic loves to relentlessly debunk nutritional myths. He advocates a low-fat, plant-based diet and has had over 10 years of experience with raw vegan diets. He lives in Montreal, Canada.

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