By Rob Stein
Washington Post Staff Writer
Tuesday, November 14, 2006
Younger women who regularly eat red meat appear to face an increased risk for a common form of breast cancer, according to a large, well-known Harvard study of women's health.
The study of more than 90,000 women found that the more red meat the women consumed in their 20s, 30s and 40s, the greater their risk for developing breast cancer fueled by hormones in the next 12 years. Those who consumed the most red meat had nearly twice the risk of those who ate red meat infrequently.
The study, published yesterday in the Archives of Internal Medicine, is the first to examine the relationship between consumption of red meat and breast cancer in premenopausal women, and the first to examine the question by type of breast cancer.
Although more research is needed to confirm the association and explore the possible reasons for it, researchers said the findings provide another motivation to limit consumption of red meat, which is already known to increase the risk of colon cancer.
"There are already other reasons to minimize red meat intake," said Eunyoung Cho, an assistant professor of medicine at Harvard Medical School, who led the study. "This just may give women another good reason."
Cho added that the findings could be particularly important because the type of breast cancer the study associated with red meat consumption has been increasing. Eating less red meat may help counter that trend.
Other researchers said the findings could offer women one of the few things they can do to reduce their risk for the widely feared malignancy. Breast cancer strikes nearly 213,000 U.S. women each year and kills nearly 41,000, making it the most common cancer and the second most common cause of cancer death among women.
"So many risk factors for breast cancer are things that you can't alter," said Nancy E. Davidson, a breast cancer expert at Johns Hopkins University in Baltimore. "This represents something women could take charge of -- something you can change to affect your risk."
Why red meat might increase the risk for breast cancer remains unknown, but previous research has suggested several possible reasons: Substances produced by cooking meat may be carcinogenic, naturally occurring substances in meat may mimic the action of hormones, or growth hormones that farmers feed cows could fuel breast cancer in women who consume meat from the animals.
Researchers have long wondered whether there might be a link between red meat consumption and breast cancer risk, but few studies have addressed the question. Those that have, including one large analysis that pooled data from eight studies, did not find any association. But the earlier studies focused on older women and did not differentiate between types of breast cancer.
In the new study, Cho and her colleagues analyzed data collected from 90,659 female nurses ages 26 to 46 who are participating in the Nurses' Health Study II, a long-term project examining a host of women's health issues. As part of the study, participants provided detailed information about their diets every four years.
When the researchers analyzed the data from 1991 to 2003, they found no overall link between red meat consumption and an increased risk of breast cancer. But when they examined the data from only the 512 women who developed the type of breast cancer whose growth is fueled by the hormones estrogen and progesterone, they found an association.
The risk increased with the amount of red meat consumed, with those who ate more than 1 1/2 servings a day of beef, lamb or pork having nearly double the risk of hormone-receptor-positive breast cancer compared with those who ate three or fewer servings per week. A serving is roughly equivalent to a single hamburger or hot dog.
"That's a pretty strong association," said Cho, who is also an associate professor of epidemiology at Brigham and Women's Hospital in Boston.
Other researchers praised the study for being well conducted but said more research is needed to confirm and explore the findings.
"The study is well done, and I'm sure it will create some interest to try to replicate the findings," said Eugenia Calle of the American Cancer Society. "But until that happens, we can't draw conclusions about whether this is a true association or something that's just been observed in a single study."
Other experts agreed but noted that the findings are consistent with a growing body of evidence that indicates that diet early in life can affect a person's health risks later on.
"This suggests that lifestyle, in this case diet, in early adulthood is important in potentially explaining your risk for premenopausal breast cancer," said Carolina Hinestrosa of the National Breast Cancer Coalition.
While it may be premature to make formal dietary recommendations based on the findings, the Nurses' Health Study II is so well respected that women should take this new analysis into consideration, she said.
But noting that earlier studies reached the opposite conclusion, Randall D. Huffman, vice president for scientific affairs at the American Meat Institute, said that research into "diet and health is known for its fluid and often contradictory conclusions. This study is a perfect example of that."
"The wisest course of action in the wake of one more contradictory study is to consume the balanced diet recommended by the U.S. Dietary Guidelines," he said.