The risk factors you can control

For the vast majority of women who worry about their breast cancer risk but are wary of taking medicine, researchers and breast cancer specialists can dispense some helpful but ultimately limited advice.

Many of the factors that contribute to breast cancer risk are pretty much beyond one’s control — women can’t change the fact that they started to menstruate at 10, have dense breasts or are genetically predisposed to the disease.

Changing social norms sometimes conspire to boost breast cancer’s odds. Many women establishing careers and marrying later delay childbearing or remain childless. But women who bear their first child after age 30, or have no children at all, are at higher risk of developing invasive breast cancer.

So, what can a woman do to nudge her risk downward? These recommendations are based on laboratory studies, clinical trials and projects that track breast cancer incidence in large populations. Most of this advice is sensible for any woman, no matter her odds of breast cancer. However, experts acknowledge that the influence of lifestyle on breast cancer risk is less well established than other factors women can’t do much about.

Assess your risk. It all starts here, says Dr. Nananda Col of Maine Medical Center’s Research Institute, who conducts research on how women weigh decisions affecting their health. The Breast Cancer Risk Assessment Tool gives a rough assessment in just a few minutes. Go to https://www.cancer.gov/bcrisktool/ and answer seven questions. Then hit the “Calculate Risk” button and you’ll get readings of your risk of developing breast cancer in the next five years and over the course of an 85-year lifetime. You’ll also see how those odds compare with the average risk for a woman your age. The numbers will give you a measure of whether lifestyle changes should suffice to curb your risk or whether you should speak to a specialist about taking further steps, such as medication or prophylactic mastectomy.

Check your weight, trim your fat, watch your waist. Excess body fat, particularly abdominal fat, raises estrogen levels, and a woman’s lifetime estrogen exposure has a powerful influence on her breast cancer risk. The role of diet in affecting breast cancer risk is less clear. Eating lots of fruits and vegetables, though widely researched, has failed to show clear benefits. But a 2006 study sponsored by the National Cancer Institute found that early-stage breast cancer patients who hewed to rigorously low-fat diets — in which fats made up fewer than 20% of calories consumed — were less likely to have a recurrence.

Being obese in childhood seems to nudge girls toward earlier sexual maturity. When a girl maintains a healthy weight, she not only drives down the odds of becoming obese as an adult, she also may delay the start of menstruation slightly, reducing estrogen exposure. Staying within a healthy weight range across your lifespan will help reduce your odds of developing breast cancer.

Exercise. Physical activity appears to help reduce a woman’s circulating levels of estrogen and its precursors. Researchers have begun to focus on how insulin resistance is linked to an increased risk of breast cancer. Since regular exercise can help improve metabolic function, it also could be expected to lower breast cancer risk. If patterns of regular exercise are established early, a woman may even stretch out her monthly cycle, further reducing estrogen exposure. Not surprisingly, women who exercise regularly have been found to have a lower incidence of breast cancer.

Reduce alcohol consumption. Consuming alcohol — the form it takes doesn’t seem to matter — raises estrogen levels. Not only does risk rise with the volume of alcohol consumed, but frequency of drinking matters too, because it means estrogen levels are elevated more often. That translates into higher and more sustained estrogen exposure, which in turn translates into greater breast cancer risk.

Skip or limit hormone replacement therapy. For most women seeking relief of severe menopausal symptoms, a regimen of estrogen and progestin (a synthesized form of progesterone) traditionally has been prescribed. The landmark 2003 findings of the Women’s Health Initiative study found that postmenopausal women who had taken this mix of hormones had a 24% higher rate of breast cancer, were more likely to have tumors that had spread beyond the breast and had far higher rates of abnormal mammograms compared with women who took a placebo. Breast-cancer risk remains elevated for about five years after hormone replacement ends. A form of therapy that uses only estrogen — generally reserved for women who have had their uterus removed — seems not to increase breast cancer risk unless it is used for 10 years or more.

Breastfeed. While the baby may be getting the bigger lifelong benefit, the mother who provides most or all of her infant’s nutrition appears to suppress her estrogen levels awhile longer, prolonging the estrogen vacation her breasts got while she was pregnant.

Take birth control pills watchfully. Oral contraceptive use appears to boost breast cancer risk slightly, though the effect declines after they are discontinued and disappears within 10 years. Since younger women are at far lower risk of breast cancer than those who have passed childbearing age, their breast cancer risk is small to begin with.

Special foods and nutrients. Clinical trials are underway to explore the benefits of several foods and nutrients, including green tea, grape seed extract and soy protein. Green tea and grape seed extract are thought to have phytonutrients that protect cells from damage and impede cancer growth, but whether and at what doses they could help are not known. Soy protein is thought to reduce breast cancer risk by blunting the effects of estrogen. Lower rates of breast cancer in Asian women, whose soy consumption is far higher than that of American women, suggests it may help. But researchers don’t know whether that effect comes from soy or something else in the environment.

melissa.healy@latimes.com