6 risk factors for breast cancer you should know

Identifying risk factors for breast cancer can be incredibly difficult, but the advance of modern medicine has helped us better understand the disease. Here are six risk factors that you should know.

Staying — or getting — slim is one of the smartest do-it-yourself strategies for sidestepping breast cancer.

• When researchers reviewed the health histories of more than 80,000 female nurses, they found that those who gained 55 pounds or more after age 18 had a 45 percent increase in breast cancer risk after menopause, compared to women whose weight stayed at healthy levels through their 20s, 30s and 40s.
• In another study, women who gained more than 60 pounds after age 18 tripled their risk of invasive breast cancer compared to women who'd put on 20 pounds or less.
• More body fat equals higher levels of estrogen, which fuels breast cancer growth.
• The good news? Women who lost 22 pounds or more after menopause and were able to keep the weight off were almost 60 percent less likely to develop breast cancer than overweight women who didn't lose weight.

Nobody can say for sure that eating less fat lowers your breast cancer risk. On the other hand, after decades of research, experts have a strong suspicion that eating more fat increases your risk.

• In the largest study ever on the connection between dietary fat and breast cancer, researchers from the US National Cancer Institute found that women whose diets included the most fat were 15 percent more likely to develop breast cancer than women who ate the least fat.
• The higher-fat eaters got 40 percent of their daily calories from fat; if you eat 2,000 calories a day, that's 800 calories' worth, the amount in 105 millilitres (seven tablespoons) of butter or oil or 225 grams (eight ounces) of cheese.
• Women who got about 20 percent of their calories from fat had no added risk.

Scientists studying breast cancer rates in Asia compared the diets and breast cancer rates of more than 3,000 post-menopausal women in Shanghai.

• Higher cancer risk was found in women who ate a more Western diet — and whose plates contained more foods like pork, poultry, organ meats, beef and lamb, along with candy, desserts, breads and milk.
• Women at lower risk ate more vegetables, soy-based products and fish.

For years, researchers wondered if diets high in soy explain why women in Asian countries have relatively low rates of breast cancer.

• The largest-ever review of studies on soy foods and breast cancer has concluded that most women who eat soy products have a slightly reduced cancer risk.
• The exceptions are high-risk women. If you're at above-average risk due to a personal or family history of breast cancer, experts suggest you avoid soy and isoflavone supplements, and limit yourself to just a few servings of soy foods each week.
• If you're taking tamoxifen or another breast cancer prevention drug, have even less. Some animal studies suggest that at high doses, soy isoflavones could stimulate the growth of estrogen-sensitive breast tumours.

Delaying pregnancy until after age 25 raises cancer risk slightly, but nursing can help even the score.

• A recent study found that older moms who breastfed their babies had fewer cases of estrogen-sensitive invasive cancer than those who did not.
• Why it works: nursing lowers levels of cancer-related hormones, including estrogen.

While some studies suggest that cigarettes have little to do with breast cancer, cutting-edge research suggests that for some women, smoking increases the risk.

• When scientists at Emory University in Atlanta reviewed 50 studies, they found a pattern: women who smoked and whose genes made their bodies slow to detoxify the carcinogenic aromatic amines in cigarette smoke were at 2.4 times higher risk for breast cancer than those whose bodies neutralized the toxins quickly. The longer the women smoked, the higher their risk.

Keep these tips in mind to help reduce your risk for breast cancer and visit your doctor for more information.