Soybeans have long been a staple of Asian diets, and in recent years they have gained popularity in Western countries as a health food.

Soybeans and their byproducts, such as soy milk and tofu, are often promoted as a low-fat, high-protein alternative to meat, and they are frequently used as an ingredient in vegetarian and vegan dishes. However, some people have raised concerns about soy’s safety, particularly in relation to cancer risk. In this article, we will explore what we currently know about soy and cancer, based on scientific research.

What Is Soy?

Soybeans are legumes that are native to East Asia. They are a rich source of protein, fiber, vitamins, and minerals, and they are low in saturated fat.

Soybeans can be consumed in various forms, such as whole beans, edamame (immature soybeans), soy milk, tofu (soybean curd), tempeh (fermented soybeans), and soy sauce.

Soy and Cancer: The Controversy

The controversy surrounding soy and cancer arises from the fact that soy contains compounds called phytoestrogens, which are plant compounds that can mimic the effects of estrogen in the body.

Estrogen is a hormone that is known to promote the growth of some types of cancer, such as breast cancer. Therefore, some people have raised concerns that consuming soy may increase the risk of cancer, particularly for women.

However, other studies have suggested that soy may actually have a protective effect against cancer. For example, some studies have found that consuming soy is associated with a lower risk of breast cancer, particularly among Asian women.

Other studies have suggested that soy may have a protective effect against prostate cancer and colon cancer.

What Does the Scientific Evidence Say?

So what does the scientific evidence say about soy and cancer risk? The answer is complex, as different studies have yielded conflicting results depending on the type of cancer, the amount and type of soy consumed, and the population studied.

Breast Cancer.

A meta-analysis of 35 observational studies published in the Journal of the National Cancer Institute in 2014 found that high soy intake was associated with a 25% reduction in breast cancer risk among premenopausal women.

However, the same analysis found no significant association between soy intake and breast cancer risk among postmenopausal women.

Prostate Cancer.

A meta-analysis of 30 observational studies published in the International Journal of Cancer in 2016 found that high soy intake was associated with a 29% reduction in prostate cancer risk in men.

However, the same analysis found no significant association between soy intake and prostate cancer mortality.

Colorectal Cancer.

A meta-analysis of 21 observational studies published in the Journal of Nutrition in 2015 found that high soy intake was associated with a 21% reduction in colorectal cancer risk.

Limitations of the Evidence

While the evidence on soy and cancer risk is promising, it is important to note that most of the studies conducted so far are observational in nature.

This means that they cannot prove cause and effect, but can only identify associations between soy consumption and cancer risk. Furthermore, many of the studies have been conducted in Asian populations, where soy consumption is much higher than in Western populations. It is possible that the results may not apply to people who consume soy in smaller quantities.

Another limitation of the evidence is that it is difficult to isolate the effects of soy from other dietary and lifestyle factors that may affect cancer risk.

For example, people who consume more soy tend to have healthier diets overall, which may also contribute to a lower cancer risk.

Conclusion

In conclusion, the evidence currently available on soy and cancer risk suggests that consuming soy may have a protective effect against certain types of cancer, including breast, prostate, and colorectal cancer.

However, more research is needed to confirm these findings and to determine the optimal amount and type of soy consumption for cancer prevention. In the meantime, consuming soy as part of a healthy diet is unlikely to increase cancer risk, and may even provide some health benefits.