Sept. 3, 2009 -- More than 70,000 breast cancer cases a year in the U.S., or 40% of all cases, could be prevented with lifestyle measures like maintaining a healthy weight, eating well, exercising, and limiting alcohol consumption, a new analysis shows.
The joint project from the nonprofit research groups American Institute for Cancer Research and the World Cancer Research Fund represents the largest review ever of the research examining lifestyle and breast cancer.
Researchers analyzed nearly 1,000 studies, including 81 conducted since the data were last examined in 2007.
"It is now very clear that lifestyle is a strong modifiable risk factor for breast cancer, but I don't think women have really gotten the message," says Cancer Institute of New Jersey epidemiology professor Elisa Bandera, MD, PhD, who helped write the report.
"Women tend to overestimate the role of genetics in breast cancer and underestimate lifestyle," Bandera tells WebMD. "I don't know how many times I've heard a patient say, 'I can't have breast cancer. Nobody in my family has it.' Women are very concerned about breast cancer, and they need to know they can lower their risk with lifestyle."
Lose Weight to Lower Risk of Breast Cancer
Perhaps the biggest single thing a woman can do to lower her risk, especially after menopause, is maintain a healthy weight.
Obesity is now widely recognized as the most important modifiable risk factor for breast cancer among postmenopausal women, and it also increases a postmenopausal woman's chance of dying from the disease once she has it.
The National Cancer Institute estimates that as many as 18,000 deaths from breast cancer each year in the U.S. could be prevented in women over age 50 by maintaining a healthy weight throughout adulthood.
About three out of four breast cancers in this age group are fueled by the hormone estrogen, which is also produced in fat tissue. Estrogen levels in overweight, postmenopausal women are 50% to 100% higher than among lean women, according to the National Cancer Institute.
Breast cancers also tend to be detected later in overweight women, mainly because tumors are harder to detect with mammography.
The joint report recommends that women stay as lean as possible without being underweight to lower their breast cancer risk.
Other recommendations include:
Get moving: Women should engage in physical activity for at least 30 minutes a day, every day. According to the National Cancer Institute, women can reduce their risk of dying from breast cancer by 25% if they remain physically active.
Limit alcohol: Women who drink alcohol should limit their consumption to no more than one drink a day.
Breastfeed: New mothers should breastfeed their infants exclusively for up to six months and then add other liquids and foods. There is convincing evidence that breastfeeding lowers breast cancer risk.
Eat healthy foods: The report recommends avoiding junk foods, limiting red meat and salt, and making fruits, vegetables, beans, and whole grains the mainstays of a healthy diet.
Nutritionist Colleen Doyle, RD, of the American Cancer Society, tells WebMD that although no single food, food group, or nutrient has been shown to lower breast cancer risk, it is clear that eating a healthy, mostly plant-based diet is protective.
A red meat and processed meat-heavy diet is now known to increase the risk for colorectal cancer, and there is some suggestion that these foods increase breast cancer risk as well.
Doyle says the research attempting to target the role of single foods, food group, or nutrient in breast cancer has largely been a bust.
"Years ago, we recommended limiting all fats and that evolved into limiting saturated fats," she says. "Now we have moved away from specific food-based recommendations to focusing on an overall dietary pattern stressing a wide variety of mostly plant-based foods."
The American Institute for Cancer Research (AICR) also recommends a mostly plant-based diet to lower cancer risk. To promote the idea, the group has developed what it calls the "new American plate" to replace the more traditional meal that has meat as its main component and refined starches as a mainstay.
AICR nutritionist Alice Bender, RD, tells WebMD that at least two-thirds of the "new" plate should be plant based, including vegetables, fruits, whole grains, or beans; no more than one-third of any meal should come from animal protein.
"This is an easy way to visualize what a healthy diet should look like," she says. "It's really pretty simple."