Does Soy Fight Breast Cancer?

If you have been researching breast cancer prevention and/or treatment, you have probably found a confusing array of information about the possible benefits or negative effects of increasing your intake of soy products. You might be wondering, is soy good for breast cancer or not? The answer is - "yes and no" - or, more simply put - "we don't know yet." Medical experts disagree about whether or not a high-soy diet can increase or decrease your likelihood of getting breast cancer, or affect your chances of recovery if you have already been diagnosed. Whether you are sufferer, or you are simply curious about staying healthy and avoiding this all-too-common disease, it's important to weigh up the pros and cons and above all, not to add extra soy to your diet before talking to your oncologist or health care provider.

What Is Soy?

Soy (also known as soya and soja) is a protein extracted from the soy bean, which grows on the soy plant. It is most commonly used in Chinese and Japanese food and in other Asian cuisines. The most well-known soy product in the West is probably soy sauce, which the more adventurous of us put on our rice or in stir-fries at home, and which most people have probably tasted in Asian restaurants or with take-out food. Tofu is also a soy protein product popular among vegetarians and vegans as an important substitute for animal protein.

How Might Soy Prevent Or Treat Breast Cancer?

Soy foods contain plant chemicals called phytoestrogens, also known as isoflavones. Some researchers believe these isoflavones have the same effect as a weak version of the female hormone, estrogen, on the body. Studies have found that boosting a woman's consumption of these weak-estrogen isoflavones may repress her normal estrogen production, which in turn may reduce her likelihood of developing breast cancer and/or hamper its growth. This is because high estrogen levels and long-term estrogen exposure (for example, through taking an estrogen-based birth control pill) have been linked a higher risk of breast cancer and may encourage its spread. If you think about this, it's logical that a major part of medical breast cancer treatment aims to reduce or totally block a women's estrogen production.

Plant estrogens like soy are believed by some researchers to lengthen a woman's menstrual cycles; giving her fewer cycles throughout her lifetime. This reduces her overall estrogen exposure and thus may decrease her breast cancer risk. Some experts also say that women with a high-soy diet tend to have lower breast density; high breast density having been associated with breast cancer in the past. Some medics cite the relatively low rate of menopausal symptoms (caused by the plummet of a woman's estrogen levels when she stops ovulating) in Asian women, who generally have high-soy diets. They say this evidence shows that soy may have a direct effect on estrogen levels. Lastly, a study published by the U.S. National Cancer Institute indicates that women who consume a high level of soy as young children have a reduced risk of breast cancer in later life.

So it seems there is reason to believe that soy could help you to avoid breast cancer or get better if you already have the disease, but this may not be true...

The Downside

You might be thinking - so far so good, eating more soy is obviously a no-brainer, but before you hit the store to stock up on tofu and soy sauce, read on. Some studies have produced the exact opposite results, showing that increasing the level of soy in your diet may make you more likely to get breast cancer and could worsen the condition in women who already have it! To find out more check out our page on the possible negative effects of soy on breast cancer.