Soy What? Debunking The Anti-Soy Health Myths

In my two years of private practice dietetics I have been hard to pressed to find a client who has had a positive opinion or perception of soy-based foods.

Men won’t eat them because they have heard that it will affect their testosterone levels.

Women won’t eat them because they harbour fears over an increased risk of breast cancer.

In my experience, both genders seem to be equally repulsed by the thought of cooking with or eating tofu and it appears that nut-based milks are displacing and outnumbering soy milk on grocery store shelves ( at least my local grocer!).

So where does that leave me?

As a dietitian, one of the biggest challenges I face on an individual and population education level is convincing people that one of the absolute keys to good health is replacing at least a portion of their animal-protein intake with plant-protein ( Check out my article here to learn more).

This is a big enough challenge as it is, but it becomes even harder when all soy-based foods are arbitrarily ruled out of people’s diets for reasons other than a potential allergy/intolerance ( which is inevitably a relative small portion of the population).

Soy What?

I am not trying to convince you that soy a superfood, nor is it a necessarily an essential component of a healthy diet.


Soy does have a secret power!

It is an exceptional alternative, from a nutritional perspective, for both meat and dairy.

Incorporating commonly available soy-based foods ( soy milk, tofu, soybeans, tempehedamame, soy nuts) is an excellent way to get protein, iron, calcium and healthy fats into your diet.

Unlike most types of meat & milk products, soy contains relatively little saturated fat and is associated with a reduced risk of a number of chronic diseases.

When you swap in low saturated fat food choices like soy into your diet for higher fat animal alternatives, you can expect a benefit to your cardiovascular & overall health ( more on this in a moment).

This is why soy is one of the important dietary components in the cholesterol lowering Portfolio Diet.

In my estimation, the inclusion of soy milk and tofu in the diet of the average person represents one of the most plausible means of increasing the intake of plant-based protein while simultaneously lowering the consumption of animal products. 

Tofu, in particular, can be manipulated and enhanced in the kitchen such that it truly is a superb meat-protein alternative both in terms of nutritional value and palette sensation.

Don’t believe me? Check out this tofu scramble recipe.

Sounds good so far right? You’d think so… but there are so many people out there who fear consuming soy. Why is that?

Why The Fear Over Soy?

Soy contains estrogen-mimicking compounds known as isoflavones (also known as phytoestrogens)  which operate in a mildly similar way to the female hormone estrogen.

For this reason, including more soy in the diet of post-menopausal women ( who produce less estrogen) has been studied as a potential means to address the symptoms of menopause ( the results are mixed).

What has happened, however, is that people seem to have latched onto this idea that soy intake profoundly impact hormone levels in the human body and thus should be avoided.

There is no strong evidence that I have come across to show this to be the case.

Unfortunately, the popular media and  would-be scholars  often end up citing studies that are either inapplicable to humans, inconclusive or of unacceptable quality to support the claim that soy is bad for you and they use these studies, in part, to spin a dark tale on the harms of soy.

When we take a look at the highest quality aggregate evidence available on the impact of moderate soy consumption on human health outcomes, we see largely positive or ( at worst) neutral effects.

Think Soy Is Bad For You? You Are Soy Wrong

I took it upon myself to track down some  of the best aggregate evidence available on soy and health outcomes.

Let’s take a look:

For Men

1. Soy does not lower testosterone levels in men: There have been undue fears that soy somehow had a negative impact on male testosterone. This is quite simply an unfounded claim. There is, in fact, no strong evidence that soy has any meaningful effect on hormone levels in men. Don’t sweat it guys, having some tofu won’t make you any less of a man.   

2. Soy intake may reduce prostate cancer risk in menProstate cancer is the #1 most commonly diagnosed cancer in Males in North America and the consumption of soy-based foods is associated with a reduction in your risk.

For Women

1. Soy has a protective ( or at worst neutral) effect on breast cancer risk: There is a massive misconception out there that woman should avoid soy because it increases their risk of breast cancer. The best available evidence suggests that, in most cases, consuming soy products may actually be protective against breast cancer.

  • Chen et al found that soy intake was protective against breast cancer in Asian countries, but this effect was not found in Western countries.
  • Fritz et al Soy consumption may be associated with reduced risk of breast cancer incidence, recurrence, and mortality. Soy does not have estrogenic effects in humans. Soy intake consistent with a traditional Japanese diet appears safe for breast cancer survivors.
  • Messina And Loprinzi Overall, the data are not impressive that the adult consumption of soy affects the risk of developing breast cancer or that soy consumption affects the survival of breast cancer patients. Consequently, if breast cancer patients enjoy soy products, it seems reasonable for them to continue to use them.
  • Trock et al  found that soy intake may be associated with a small reduction in breast cancer risk.

2. Soy intake may reduce the risk of other women’s cancersA review of the best available studies have shown that women who eat more soy  tend to have a lower risk of ovarian and endometrial cancer.  Further evidence also suggests that women who consume more soy may be  protected from both colorectal and gastrointestinal.

3. Soy has no known negative effects on postmenopausal womenFor all the talk about soy products “tampering” with female hormones leading to ill effects, there is no evidence to suggest that this is the case at all based on the latest data.

The studies that I have linked to here are among the best available we have on the subject of soy and human health and are based primarily on aggregate data of numerous studies.

You may encounter one-off studies in particular contexts ( cough, animal studies)  that may show soy in a negative light, but it’s important to understand that critical health decisions are rarely/never made on the basis of single studies because , realistically, things can and will be misrepresented.

Final Thoughts

No detractor of soy will be able to produce high quality aggregate evidence that it is dangerous for human consumption, because that evidence simply does not exist. 

Again, I believe that introducing more tofu and soy milk ( among other soy products) in place of animal alternatives is a very practical step that the average person can take on a daily basis to improve their health in the long-term.

Don’t sweat it if you truly don’t like soy though because there are PLENTY of other plant-based choices out there.

Until next time,

Andy De Santis RD MPH