Can Soy Protect Against Prostate Cancer?

May 08, 2020

Can soy, a popular meat substitute, protect against prostate cancer?

For some people, soy is synonymous with health. Many labeled “healthy foods” are derived from this popular Asian-native soybean, like tofu and soymilk. Soy is also a popular meat substitute, especially for burgers, hot dogs, and meatballs. Fermented soy is made into foods like soy sauce, bean paste, and tempeh.

Soy is actually one of the more nutritious legumes. It is full of fiber, polyunsaturated fats, potassium, magnesium, and other vital vitamins. It also contains all the required amino acids—the building blocks of protein—which is why soy is popular among vegetarians and vegans as a source of protein.

But is soy a wonder food when it comes to prostate cancer? So far, the science is a bit cloudy. For example, this 2017 study in the International Journal of Cancer suggests eating foods high in certain soy compounds may actually raise the risk of aggressive prostate cancer. The researchers looked at the dietary habits of about 27,000 men who filled out dietary questionnaires and compared the information to their risk of developing prostate cancer over 11.5 years. They found that those who ate the most isoflavones—a plant chemical found in soybeans—were much more likely to develop advanced prostate cancer than those who consumed the least. (Men in the highest group of isoflavones consumed 0.75 to 2.03 milligrams [mg] a day. In comparison, a 3-ounce serving of tofu has 20 mg of isoflavones, and 1 cup of soymilk has 30 mg.) But let’s look closer at the findings. The researchers found no link between eating the soy compounds and getting prostate cancer or non-aggressive prostate cancer. The connection was only with late-stage prostate cancer patients, which is a stage involving a greater likelihood of further spread of cancerous cells. Still, the study only showed an association, not cause and effect, and the scientists noted that more research is needed to confirm the results.

Other studies have shown a more decisive role for soy. Some research has suggested that consuming soymilk or isolated soy isoflavones makes PSA levels rise at a slower rate, according to the American Institute for Cancer Research. The effect tends to be stronger in some men than others, which suggests a genetic component or other factors may be at play.

There is also the fact that prostate cancer rates continue to be lower in Asian countries (where soy is a diet staple) compared with Western countries. This could be due to equol, a by-product of soy produced by gut bacteria. Some research has found that equol is associated with a lower prostate cancer risk. However, not everyone can break down soy to make equol. In fact, one study found that American men produce lower amounts of equol compared with Japanese and Korean men. So, can non-Asian men produce enough equol to protect themselves against prostate cancer? Likely not.

Soy could have an indirect effect on the health of men with prostate cancer. For instance, soy meat substitutes can help men reduce their intake of red meat, high amounts of which are associated with a higher risk of heart disease. Some research has found that soy may help lower cholesterol levels, too.

One caveat about soy is that it may expose men to extra estrogen. The isoflavones in soy are a type of phytoestrogen, which may have a similar effect on the body as estrogen. Soy aficionados claim that isoflavones block estrogen receptors, therefore blocking your body’s estrogen from attaching to the receptors causing no estrogenic effect.  One research article has shown that soy does not increase levels of estrogen in men.

Too much estrogen has been associated with a higher risk of some cancers among women, especially breast cancer. But men don’t really need to worry about this.

So, if you are confused about soy and prostate cancer, that’s fine because everyone else is confused too. Whether it may protect against prostate cancer or help to manage your diagnosis is still unknown. Until then, I think it’s okay for men to enjoy soy in moderation.

Also, it’s not a good idea to think any single food is a panacea. It is best to eat a variety of optimal, clean foods that include broccoli, Brussels sprouts, and cauliflower, cruciferous vegetables they are called and have shown to have prostate cancer protection. Again, no one food has a magic cure for prostate cancer or any disease.

Feel free to consume one to two daily servings, such as 1 cup of soymilk, or 1 cup of tofu or tempeh a couple of times a week. I’d avoid heavily processed soy products like soy ice cream, soy burgers or soy hot dogs. Soy based or not, these foods are not healthy choices.

Be Well,

Dr. Geo

 

 

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