Seven things you should know about breast cancer risk

There’s no one big way to reduce your risk for breast cancer, but a combination of approaches could make a difference.

In recent years, the statistical picture of breast cancer has brightened, thanks to early detection and advances in treatment. More tumors are being caught at an early stage, the rise in incidence of the disease has slowed, and the death rate has dropped. Nevertheless, breast cancer is still the most commonly diagnosed cancer in women and the second most likely (after lung cancer) to take their lives.

Data aside, breast cancer looms large in our health concerns because most of us know it personally. Some of us have had the disease ourselves, and others have experienced it through friends or relatives. Particularly unsettling is its seeming randomness: Nothing seems to explain why one woman develops breast cancer and another doesn’t. Granted, family history and certain gene mutations can substantially increase risk. But such factors aren’t involved in most breast cancers. Moreover, we can’t do much about them, or about many of the other risks associated with the disease, including older age (the 10-year risk of developing breast cancer jumps from one in 48 at age 40 to one in 26 at age 60), early menarche (first menstrual period), having no children (or bearing the first at a later age), and late menopause.

Researchers have found associations between certain nutritional factors and breast cancer risk, although not all associations have resulted in risk-reducing strategies. For example, the American Institute for Cancer Research has found there just isn’t enough evidence to recommend for or against many of the things that once seemed promising, such as eating more soy or taking supplements like vitamin E, vitamin C, or selenium. Researchers have found little support for the common assumption that dietary fat increases breast cancer risk, and the evidence that fruits and vegetables are protective is weaker than was once thought.

But evidence is accumulating that we can lower our risk through certain healthy lifestyle choices, such as increased exercise, and clinical studies suggest some medical strategies. Medicine had much less to offer as recently as 1996, when the best we could say was, “Unfortunately, there is little we can do to reduce our risk of breast cancer.” New information is developing all the time, but for now, here are seven factors that could affect your risk and what you can do about them:

1. Weight gain

Many studies show that weight gain is a risk factor for breast cancer after menopause. An American Cancer Society study found that women who gained 20 to 30 pounds during adulthood (that is, after age 18) were 40% more likely to develop breast cancer after menopause than women who gained no more than 5 pounds. The link is estrogen, which is believed to promote the development of breast cancer. Fat tissue converts precursors in the body into estrogen, keeping the hormone in circulation even when ovarian production stops at menopause.

A Nurses’ Health Study (NHS) investigation published in 2006 in the Journal of the American Medical Association concluded that weight gain since age 18 or since menopause increases the risk of breast cancer in postmenopausal women, except in those who are using postmenopausal hormone therapy. (In women taking hormones, the external source of hormones is much higher than what can be made by body fat, so the fat doesn’t contribute to increased risk.) The NHS researchers also found that losing 22 pounds or more after menopause decreased the risk of breast cancer.

What to do? Do all you can to avoid gaining weight as an adult, and try to enter menopause at a healthy weight. If you’re overweight, try to lose weight.

2. Activity level

Many studies have shown that women who engage in regular physical activity have a lower risk of developing breast cancer compared with women who are sedentary. You may reduce your risk by 20% to 30% by getting three to four hours of moderate to vigorous weekly exercise (brisk walking and yoga are examples of moderate exercise; jogging, cross-country skiing, and aerobic dance are vigorous). Exercise also reduces the risk of recurrence if you have been treated for breast cancer.

Regular exercise works in several ways. It can help you achieve and maintain a healthy body weight; it may influence circulating hormones and reduce the exposure of breast tissue to estrogen; and it can influence levels of insulin and insulin-like growth factors, which have been linked to the growth of breast cancer cells.

What to do? To reduce breast cancer risk, the American Cancer Society recommends moderate to vigorous activity for 45 to 60 minutes on at least five days of the week. Formal exercise (such as walking programs, swimming laps, cardio-fitness workouts, or aerobics classes) is a good way to get a sustained workout. But you can also do housework or gardening activities — as long as you breathe as hard as you would during a brisk walk or jog.

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Seven things you should know about breast cancer risk