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    Soy and Breast Cancer: 5 Myths and Facts

    By Sharon Liao
    WebMD Feature
    Reviewed by Jennifer Robinson, MD

    You may have heard that you shouldn’t eat soy if you are at risk for breast cancer. But then you see headlines saying that it could protect against the disease. So what’s the truth?

    Even for health-savvy people, telling fact from fiction can be tricky.

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    Knowing the real deal is important, especially now that soy is more common in the American diet. Along with its traditional forms of edamame, tofu, tempeh, and miso, soy is also a popular low-fat source of protein. It’s in soy milk, meat substitutes, cereal, baked goods, energy bars, and more.

    Should you avoid these foods or eat more of them? The simplest answer is to think “whole” -- as in, as close to nature as possible -- so you don’t get too much.

    For more clarity, get the truth behind these five common myths.

    1. Myth: All soy foods raise your risk for breast cancer.

    There’s no need to banish tofu and edamame from your diet.

    “For years, soy got a bad rap because of its isoflavones,” says Marleen Meyers, MD, director of the Perlmutter Cancer Center Survivorship Program at NYU Langone Medical Center.

    These plant-based chemicals are similar in structure to estrogen. Most breast cancers are sensitive to estrogen (or, as doctors say, “estrogen-receptor-positive” or “ER-positive,”) which means that estrogen fuels their growth.

    “So there was a fear that soy could act as estrogen in the body and stimulate cancer cells,” Meyers says. “It was spread on blogs, and people would tell each other to avoid soy.”

    But a steady stream of studies showed that a diet high in soy didn’t increase the chances of developing breast cancer and may even reduce that risk.

    In one study of more than 73,000 Chinese women, researchers found that those who ate at least 13 grams of soy protein a day, roughly one to two servings, were 11% less likely to develop breast cancer than those who got less than 5 grams.

    “In Asian cultures, where people eat a lot of soy from a young age, there are lower rates of breast cancer,” Meyers says. And in those societies, people still eat soy in its traditional forms.

    Meanwhile, another analysis of eight studies showed that those who got the most soy isoflavones -- about the amount in a serving of tofu - were 29% less likely to get the disease compared to those who got the least.

    “As part of a healthy diet, whole soy foods are safe,” says Denise Millstine, MD, director of integrative medicine at the Mayo Clinic in Scottsdale, AZ.

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