The Diet That May Fight Breast Cancer
Can eating right really protect you against the C word? The latest research points to yes.
Getty ImagesWhich of these foods lowers your chances of developing breast cancer the most: blueberries, salmon or quinoa?
Sorry—trick question. The truth is, we don't know. While it's true that individual foods contain chemicals that may lower cancer risk, the most recent thinking is that their cancer-fighting powers work best when they're eaten as part of an overall healthy dietary pattern. "It's not just what you eat—it's also what you don't eat," explains Cynthia Thomson, PhD, professor at the College of Public Health at the University of Arizona. "Adopting the right eating plan and getting regular exercise can significantly lower your risk of breast cancer. There's no medication that can provide that kind of protection for average-risk women."
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Read on for the simple nutritional moves that can make a huge difference to your health.
Consume colorful produce
Fruits and veggies with a deep hue (think dark green spinach, red tomatoes, orange carrots and the like) are packed with carotenoids, plant pigments that act as antioxidants and could lower your breast cancer odds. In fact, Harvard Medical School researchers reported in 2012 that women with carotenoid levels in the top 20% of the measured range had a 15 to 20% reduced risk of breast cancer compared with those who had the lowest levels.
"The evidence is pretty convincing, and it makes sense from a biological perspective since carotenoids soak up dangerous free radicals that can lead to DNA damage and cancer," says Heather Eliassen, ScD, lead author of the study. "We found a strong reduction in the risk of estrogen-receptor-negative [ER-] breast cancer in particular, which is exciting because that type of tumor, while rarer than estrogen-receptor-positive [ER+] tumors, tends to be aggressive."
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But you don't have to limit yourself to only the most eye-popping fruits and vegetables. It turns out that cruciferous vegetables like cauliflower might lower risk too. And University of Arizona researchers recently reported that postmenopausal women who most closely adhered to the American Cancer Society's Guidelines on Nutrition and Physical Activity for Cancer Prevention, which include eating at least 2 1/2 cups of fruits and vegetables a day (no matter what kind or color), had a 22% lower risk of breast cancer than those who complied the least.
So if you like kale or Swiss chard, that's great. But don't stress out about cramming in any one type of berry or leaf to the exclusion of everything else. "The message here is not only to eat your vegetables but to eat lots of them—and eat a diverse mix," Thomson says. "Every kind of produce contains different vitamins and antioxidants, and they seem to work together to provide protection against cancer."
Downing lots of fruits and veggies likely also reduces your risk of esophageal, colorectal, gastric and lung cancers, per a research review by the Physicians Committee for Responsible Medicine (PCRM), a nonprofit based in Washington, D.C.
Eat less saturated fat
The question of whether dietary fat plays a role in breast cancer has proven controversial; some studies have found a link, while others haven't. But when European researchers recently looked at breast cancer by subtype, they found a connection between dietary fat intake and ER+/progesterone-receptor-positive (PR+) breast cancer, the most common type. The clearest culprit was saturated fat, found in red meat, butter and dairy products. Women in the study who consumed the most had a 28% higher risk of ER+/PR+ cancer than those who ate the least.
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It's been hypothesized that saturated fat might pose a risk by raising levels of estrogen, which in high amounts can fuel ER+ tumors. That's supported by the fact that researchers found no connection between saturated fat consumption and ER-/PR- cancer (which isn't fueled by estrogen), according to Sabina Sieri, PhD, lead author of the study.
This isn't the first time saturated fat has been implicated in breast cancer. Earlier this year, after looking at the diets of almost 90,000 women, Harvard researchers reported that high intake of red meat early in adulthood is associated with a higher risk of breast cancer among premenopausal women. And in a series of studies last year, Duke University researchers showed that a by-product of cholesterol known as 27HC mimics estrogen and can drive the growth of ER+ breast cancer. "Our findings suggest that reducing cholesterol is one way to lower breast cancer risk," says Donald McDonnell, PhD, chair of the department of pharmacology and cancer biology at Duke University School of Medicine.
The takeaway: Limit saturated fat to 10% of your total daily calories. Consume plant and vegetable fats and oils, like olive oil, canola oil, avocados and nuts, instead of butter and other sources of saturated fat, and avoid trans fats (like those in some margarines, packaged cookies and crackers), which, like saturated fat, can raise LDL ("bad") cholesterol levels. "Substitute red meat with fish, poultry or beans whenever possible," Eliassen adds.
Avoiding red and processed meat may also lower your risk of colorectal cancer, according to the PCRM study.
Next Page: Watch your drinking [ pagebreak ]
Watch your drinking
Solid evidence continues to build that having more than one alcoholic beverage a day raises one's chances of breast cancer. "It increases risk by about 20%," says Cheryl Rock, PhD, professor in the department of family and preventive medicine at the University of California, San Diego School of Medicine.
Several years ago, one of the most thorough studies of booze and breast cancer, published in JAMA, found that risk starts at very low rates of consumption—less than a drink a day—and marches upward the more you imbibe. And women diagnosed with ductal carcinoma in situ—a noninvasive form of breast cancer—who drink more than others seem to have a greater chance of receiving a second diagnosis down the road.
Why is alcohol problematic? One theory, Rock explains, is that it raises blood levels of estrogen, which promotes the growth of breast cells, including those that are precancerous.
But that doesn't mean you can't ever enjoy a glass of wine. Unless you have significant risk factors, a glass of wine a day is probably fine, Rock says—especially since there are heart-health benefits associated with that amount. But if you have a strong family history or a BRCA1 or BRCA2 gene mutation, it's wise to drink rarely (or never), says Susan Levin, RD, director of nutrition education for the PCRM. "For high-risk women," she says, "the heart-health benefits don't outweigh the cancer dangers."
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The PCRM study said that limiting alcohol may also reduce the risk of cancers of the mouth, larynx, esophagus, rectum and colon. We'll toast—only once—to that.
How Safe Is Soy?
Ask 10 friends whether soy is good for you, and you'll get entirely different answers. That may partly be because tofu, soybeans and soy milk contain isoflavones, substances our bodies convert into estrogenlike chemicals shown to sometimes stimulate the growth of breast cancer cells in lab animals.
But studies of people who eat a lot of soy suggest that these chemicals don't have that effect on us. "We now know that plant estrogen doesn't increase the risk of breast cancer and may even protect women who have had breast cancer from a recurrence," says Susan Levin, RD.
In 2012, Marji McCullough, ScD, strategic director of nutritional epidemiology for the American Cancer Society, concluded that moderate consumption of soy foods appears to be safe for all women, including those who have had breast cancer. (The jury is still out on soy supplements containing high concentrations of isolated soy compounds.) And a review in the American Society of Clinical Oncology 2013 Education Book reported that eating 10 to 20 milligrams of isoflavones from soy foods (roughly one to two servings) a day may be linked with a reduction in risk. Tell your friends!
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Don't microwave in plastic (or put hot food or beverages in plastic containers): Scientists warn that estrogenlike chemicals could leach into your food by doing so—possibly even if you're using plastic that's free of a well-known culprit called bisphenol A (BPA), according to an article published in the journal Environmental Health Perspectives.
Eat more fresh food: Why? BPA and other hormone disruptors can be in food-can linings and plastic packaging. A study by Silent Spring Institute and the Breast Cancer Fund found that switching to a fresh-food diet and avoiding cans and plastic packaging led to the reduction of subjects' BPA levels by more than half in just three days.
Don't char your meat: "Those black lines and crispy bits contain heterocyclic amines [HCAs]—compounds associated with an increased risk of breast cancer," says Susan Levin, RD. (Grilling veggies is fine, she says, since HCAs are formed only from cooked animal muscle.)