Red Meat May Raise Breast Cancer Risk, Study Suggests
Eating more fish, nuts, poultry may help, but findings don't prove cause-and-effect
"This study, with extremely weak associations based on self-reported food intake, doesn't add much to our current knowledge on this complex condition," she added.
However, Farvid said that red meat has been thought to increase the risk of breast cancer in different ways. Cancer-causing "byproducts created during high temperature cooking of red meat" may be to blame, she said. Another possibility: hormones used to increase growth of beef cattle. Also, she noted, "food preservatives such as nitrate and nitrite in processed meat can also be associated with elevated risk of breast cancer."
The report was published June 10 online in the BMJ.
For the study, Farvid and her colleagues collected data on almost 89,000 women, aged 26 to 45, who took part in the Nurses' Health Study II. The women completed a questionnaire on diet in 1991, 1995, 1999, 2003 and 2007, according to the study.
Participants were asked about daily consumption of unprocessed red meat, such as beef, pork, lamb and hamburger, and processed red meat, such as hot dogs, bacon and sausage.
They were also asked how much poultry (including chicken and turkey); fish (including tuna, salmon, mackerel and sardines) and legumes (including beans, lentils, peas and nuts) -- they ate each day. The responses were ranked from "never or less than once per month" to "six or more per day."
Over 20 years of follow-up 2,830 women developed breast cancer, according to the study.
To try to determine red meat's role in the risk for breast cancer, Farvid's group also factored in differences in height, weight, race, family history of breast cancer, history of benign breast disease, smoking, menopausal status, hormone and oral contraceptive use. They also took into account the participants' diets when they were teens.
"This paper very usefully translates findings about the associations between meat intake and breast cancer risk into specific, actionable, risk-reducing strategies," said Dr. David Katz, director of the Yale University Prevention Research Center.
"In general, replacing one daily serving of meat with legumes, fish or poultry has the potential to reduce breast cancer risk by a relative 15 to 20 percent. That is clearly enough to matter," said Katz.