Minimize your breast cancer risk—and worry—by focusing on factors within your control
By Catherine Monahan
If you consider the friends and relatives in your life who have breast cancer, you may well conclude that the pattern of the disease doesn't make sense. And you'd be right—to a point. There's much we don't understand about breast cancer. Yet, as more studies are conducted, researchers can now pinpoint with certainty a number of factors that increase a woman's risk. And there's good news: We also know with certainty what can minimize the risk.
Some factors are out of your hands: To start, being a woman and getting older increase risk—most breast cancers occur in women older than 50. Men develop breast cancer, but the incidence is exceedingly rare. Then there's family, though genes account for only about 5 percent to 10 percent of all breast cancers. Your risk is somewhat higher if your mother or sister develops the disease, particularly if onset is prior to menopause. That means the remaining 90 percent of breast cancers are caused by something else.
How does it happen? Breast cancer, as it's now understood, is a two-step process. First, something injures a breast cell's DNA. It might be radiation exposure or an environmental carcinogen. Another factor, most likely hormonal, then stimulates cell growth in the damaged cell. This hormone promoter may be influenced by alcohol, diet, obesity or exercise habits. Here's a look at each of those risk factors, beginning with hormones themselves.
Estrogen, the hormone responsible for a woman's sexual development, also contributes to breast cancer. The problem is not estrogen itself, but rather the total amount you're exposed to over the course of your lifetime.
Girls who begin their periods before age 12 and women who experience late menopause run an increased risk of breast cancer. That's because menarche (the start of menstruation) turns on estrogen production and menopause usually switches it off. The longer a woman menstruates, the greater her lifetime exposure to estrogen. Not all estrogens are the same, however. Current research has pinpointed certain estrogen metabolites—16-hydroxyestrones and 4-hydroxyestrones—as cancer promoters, whereas other metabolites, such as 4-methoxyestrone, actually protect against cancer. The breast cancer-estrogen link is still not completely clear.
Breast cancer risk is also higher for women who don't have children or who give birth after age 30. The reason? Pregnancy and breast-feeding both slow estrogen production, and the sooner it happens, the better. Breast-feeding for at least six months can cut a woman's risk to half what it would be had she never nursed a child.
While you probably won't decide to have another child just to lower your cancer risk, you are in control of the decision to add, or not to add, more hormones to the mix. "It's generally now thought that estrogen birth control pills and estrogen-containing medicines such as hormone replacement therapies increase the risk of developing breast cancer," says Ben Chue, MD, oncologist and medical director of the Seattle Cancer Treatment and Wellness Center. "It's not a big risk, but a risk nonetheless." Only estrogen birth control pills are risky, and that's if you've been taking them for more than five years. Progesterone birth control pills tend to have a protective effect, says Chue, although some research has indicated the contrary. According to one study, progestins—progesterone from synthetic progesterone derivatives—used in both birth control pills and HRT—may actually increase the risk of breast cancer. Hormone replacement creams derived from herbs or soy also may have estrogenic effects, so use them carefully as well.
Hormones you're unwittingly exposed to may do similar damage. Polluting chemicals such as DDT and PCBs are endocrine disruptors—chemicals that act like hormones. These persistent pollutants, many from industrial sources, linger indefinitely in waterways and eventually show up in the fatty tissues of fish, animals and some people. Once in the body, such hormone-mimicking chemicals (also called xenoestrogens) may stimulate rapid breast cell replication. No study has yet linked DDT or PCBs to breast cancer risk, but suffice it to say, they're suspect.
What You Drink
Alcohol's tie to breast cancer has been bandied about with some uncertainty for more than two decades. The latest consensus is that if you drink every day, you're increasing your risk. Alcohol binds up liver metabolism, allowing estrogen to linger in the bloodstream. Studies show risk varies according to age and the amount of alcohol consumed.
Researchers who reviewed previous alcohol studies from several countries concluded that women who had more than three drinks a day were at higher risk for breast cancer than nondrinkers (Journal of the American Medical Association, 2001, vol. 286, no. 17). In Italy, where women partake of wine routinely, it's likely that nearly 15 percent of breast cancers are related to alcohol use. That number drops to 2 percent in the United States. Another study suggests that drinking any amount at all increases an older woman's risk of dying from breast cancer by up to 40 percent (Cancer Causes and Control, 2001, vol. 12, no. 10). In both cases, risk was proportional to the amount women drank, and it didn't seem to matter whether it was wine, beer, or whiskey.
Does that mean giving up drinks with dinner? Not necessarily. Authors of the JAMA study recommend drinking only occasionally or having no more than one drink a day. If you choose to drink more, take extra folic acid, which appears to reduce the risk of breast cancer associated with alcohol use. If you have an existing breast cancer, or are at high risk, it's probably wise to skip the cocktails.
Being overweight or obese is a serious risk factor for developing breast cancer after menopause, especially if you wear your weight around the middle. According to the Iowa Women's Health Study, of 41,000 women questioned about their health and lifestyle habits, those with large waist circumferences who also had a family history of breast cancer ran the highest cancer risk. But weight can be lost, and by dropping a few pounds, you're also moderating hormone levels. Most women's bodies continue to produce estrogen after menopause, not in the ovaries, but in fat cells. On average, overweight women have nearly double the estrogen levels of thin women.
To tackle your extra weight, keep calories down and choose a nutrient-dense diet instead of sugary foods, advises Mark Brignall, ND, of the Seattle Cancer Treatment and Wellness Center. Once you've done that, exercise. Aerobic activities such as swimming, biking, and running will help you slim down, as will weight training.
Work It Off
In addition to helping shed hormone-promoting pounds, exercise lowers estrogen production at its source—the pituitary gland. The effect can be so strong that some professional female athletes go months between periods. For the same reason, girls who are athletic from a young age often delay their periods until they are 16 or older, which decreases their risk of breast cancer later. Because it increases immunity, regular exercise may also enhance the body's ability to deflect cancers.
Exercise needn't be strenuous to be effective. Older women who consistently walk half an hour four times a week are still making a dent in estrogen levels.
A high-fat diet's impact on breast cancer has been the subject of many conflicting studies, says Brignall. "But overall, I think the information is pretty good that by reducing fat, you can reduce your risk of breast cancer."
The evidence indicates that saturated fats are to be avoided, but polyunsaturated fats, such as omega 3s found in fish and flaxseed, can actually help protect against cancer. Include those and other cancer-fighting foods in your daily diet. A high-fiber diet is another good place to start, says Brignall, because it lowers serum estrogen. Eat more whole grains, fruits, and vegetables, which are not only high-fiber but lower cancer risk on their own, possibly because of their high antioxidant content.
A varied diet is the surest way to get the most benefit from foods, but it's fine to double up on crucifers, the vegetable family that includes broccoli, Brussels sprouts, cabbage, and cauliflower (see "Tea for Breast Care"). What makes crucifers special is indole-3-carbinol, a chemical that affects estrogen levels. It influences liver metabolism of estrogen in such a way that "estrogen circulating in the bloodstream is less potent," says Brignall.
And then there's soy. Despite the accepted estrogen-lowering qualities of soy products, laboratory studies have raised the possibility that soy isoflavones such as genistein may speed breast cancer growth in women who already have the disease or are at high risk. But there are other studies that show genistein's inhibitory effect on breast cancer cells. Given that many women rely on soy to relieve menopausal symptoms, it's important to talk to your doctor about the amount of isoflavones you're eating or taking in supplement form. Finally, if you're wondering about your morning coffee, rest easy. There's no evidence that caffeine ups your odds of breast cancer.
Putting It All Together
It's no surprise that risks, and what you can do about them, overlap in complicated ways. But the bottom line is simple: The healthy diet and exercise choices you make now will influence estrogen levels for the better—and for all the years to come.
Catherine Monahan is a health writer and a frequent contributor to Delicious Living.