Will eating soy foods such as tofu affect my risk of breast cancer? What about Alzheimer's?

Will eating soy foods such as tofu affect my risk of breast cancer? What about Alzheimer's?

Michael Roizen, M.D.

Michael Roizen, M.D.

As chief wellness officer and chair of the Wellness Institute of the Cleveland Clinic, Michael F. Roizen, MD, is on a mission to inform... Read more

It appears that eating large amounts of soy (50 grams a day, which is about 1.7 ounces or more, or a small piece of tofu) actually protects you from breast cancer. But whether soy increases risk of age-related memory dysfunction or not is unclear. Your question really relates to estrogen, which is found in soy as phytoestrogens (there are 50 estrogen-like compounds in a typical soybean), relatives of your native (or bio-identical) estrogens, and whether soy protein protects blood vessels or ages them. The answer: Maybe and probably. Most data on native estrogen shows that it causes or allows the normal relaxation response in blood vessels to occur, which protects your blood vessels and keeps them and your brain healthy.

Now it gets a little tricky, so bear with me as I try to explain this. The estrogen found in soy acts as an antagonist to your native bio-identical hormone. But being chemically similar doesn't mean it produces the same estrogenic effect in the body. In fact, phytoestrogens actually block your normal estrogen (or even the bio-identical estrogen you might take in menopause) from getting to your typical estrogen receptor cells.

What that means is if the isoflavones in soy antagonize your native bio-identical estrogen, as is probable, then soy decreases your risk of breast cancer (which is usually increased by your native estrogen's effects) and it increases chance of stroke (since your native estrogen decreases risk of stroke). The tricky part is that soy's phytoestrogens act as antiestrogenic at most of your estrogen receptors — they are fake outs.

So how can you reap the health benefits of soy and not up your odds of stroke? Data from the Women's Health study and other places (see Chapter 11 in "YOU: Staying Young," where Dr. Oz and I review this topic) shows that starting at age 40, you need to be taking an aspirin with estrogen. Check with your doc if taking two baby aspirins a day is right for you.

To help with overall immunity and heart health, it's important to also make sure that you get enough vitamin D3 (have your level measured and shoot for a level above the 50s) and omega-3s (900 mg of DHA a day is what we recommend) to help keep your brain, heart and breasts as young as possible.

An added bonus: The soy and aspirin combo may not only decrease your chances of breast cancer and stroke, but also lower your risk of memory dysfunction. Most memory loss in old age is not Alzheimer's but the result of vascular disease. And even Alzheimer's disease is made worse by vascular disease. While we don't know of any direct effect of estrogens on a basic mechanism of Alzheimer's disease, we do know that estrogen affects the health of the vascular system, allowing blood vessels to relax. So we think you can decrease vascular disease throughout with the use of bio-identical estrogen combined with two baby aspirins. I tell patients never to take any estrogen without the aspirin because estrogens increase the risk of clotting.

More than anything, what we've learned in the past 20 years is that you get to control your genetic tendencies. You acquire your mother's meat loaf recipe, her smoking habit and tendency toward high blood pressure. But you also have the power to change all three.