Can soybeans cause cancer?

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
How soy lands in the "harm" camp has to do with the protein receptors contained in and on the surface of many human cells, including cancer cells. Receptors have a particular affinity for certain molecules and are very finicky about what shaped molecule they will accept. It must be a fit, like a key fits a lock. The hook-up is important because it tells a cell how to behave. It can be a neurotransmitter chemical or a hormone such as estrogen, even a specially designed drug. Some "keys" will activate a cell's activity (agonist) and some will block one from occurring (antagonist).
Studies show soy can do both.

Cells can't distinguish soy molecules’ plant-derived estrogens from human estrogen because it has the same shaped key. Some cancer cells have estrogen receptors that fuel their growth. In fact, one treatment strategy for women with estrogen-positive breast cancer is to rid or block the body of any estrogen.

The theory holds that the phytoestrogens in soy may act similarly to human estrogen causing breast cancer cells to grow.

On the other side of the argument, some think that the plant estrogen could protect against breast cancer by hedging into the receptor slot in place of human estrogen, derailing estrogen's ability to fuel cancer growth.

A study published in the Journal of the American Medical Association (December 2009) tracked 5,000 women with breast cancer living in Shanghai, China and found that those who ate diets high in soy - more than 15 grams a day - had a 29% reduced risk of death and a 32% decrease in the risk of cancer recurrence.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.