For Immediate Release: October 1, 2009
NN: Reducing Breast Cancer Risk: Which Steps Are Best?
Week of October 5, 2009
Contact: Alice Bender, (202) 328-7744
Reducing Breast Cancer Risk:
Which Steps Are Best?
Karen Collins, MS, RD, CDN
American Institute for Cancer Research
Since there are several types of breast cancer, we shouldn’t be surprised at how challenging it is for researchers to identify which steps can most effectively reduce risk. Study results vary about the impact of vegetables, fruits, whole grains, total fat and different types of fat. However, the American Institute for Cancer Research (AICR) recently published an update to its 2007 expert report looking at lifestyle and breast cancer risk. This is the largest review of research on this topic ever conducted and has confirmed that weight control, regular physical activity and limitation of alcohol are the foundations of a lifestyle to lower breast cancer risk.
A Healthy Weight
The landmark 2007 report and now the update conclude that overweight convincingly increases risk of postmenopausal breast cancer. As a woman’s body weight increases so does her risk and excess body fat at the waist may be specifically tied to postmenopausal breast cancer risk.
A 2009 review of research on postmenopausal breast cancer in the Journal of the National Cancer Institute also identifies weight control as one of the most important steps to reduce risk. Nine large population studies linked adult weight gain of 22 to 44 pounds with up to a 50 percent increase in risk, and gains above that are linked with a 45 to 87 percent increase in risk.
Greater body fat seems to increase body levels of estrogen after menopause, which explains its link to estrogen-sensitive breast cancer. Increased body fat also leads to increased levels of insulin and insulin-like growth factors, increasing risk of even estrogen-negative breast cancer.
The AICR report convincingly links regular physical activity to lower risk of postmenopausal and probably of pre-menopausal breast cancer as well. In their analysis of multiple studies researchers found that two hours of moderate physical activity each week will begin to decrease postmenopausal breast cancer risk. The JNCI review notes that in several large studies, women with the highest physical activity levels show 14 to 20 percent lower breast cancer risk than those least physically active.
Physical activity potentially protects against breast cancer through strengthening the immune system as well as reducing levels of both reproductive and insulin-related hormones, and through its impact on weight control. There is no question that activity matters, rather, the question is how much and what types provide optimal protection. A minimum of thirty minutes a day of moderate activity is the current overall health recommendation.
According to the AICR report, limiting alcohol is the step that most clearly reduces risk of both pre- and postmenopausal breast cancer. Combined analysis of many studies consistently shows a 5 to 10 percent increase in breast cancer risk with each daily standard alcoholic drink. One such drink equals 12 ounces of beer, 5 ounces of wine or one-and-a-half ounces of 80-proof liquor. One analysis in the JNCI review showed that among postmenopausal women, those who drink alcohol show a greater risk than those who drink no alcohol.
One more step that clearly reduces risk of pre- and postmenopausal breast cancer: breastfeeding. Beyond these four links, the answers get much less clear. The JNCI review of research concludes that women can reduce their risk of postmenopausal breast cancer with a low fat diet. However, the AICR report showed some indication that total dietary fat may be associated with increased risk, but more research is needed.
Eating plenty of vegetables, fruits, whole grains and beans is clearly recommended for overall health, but unless the low calorie content of these foods is used to support a healthy weight, research is inconsistent about any direct breast cancer protection. However, researchers are studying whether benefits may vary with particular foods or personal genetic differences.