Put down that bacon double-cheeseburger, ladies. Just put it down.

A big new study has shown that women who ate the most red meat increased their chances of getting breast cancer by nearly 25 percent. The 20-year-long study tracked the eating habits of nearly 89,000 women.

On the plus side: Replacing a daily serving of red meat with a combination of fish, legumes, nuts, eggs and poultry as protein sources appeared to lower the risk of breast cancer by 14 percent, researchers said.]
Doing this diet switch “during early life seems beneficial for the prevention of breast cancer,” lead researcher Maryam Farvid of the Harvard School of Public Health's Department of Nutrition told HealthDay.

Women who ate 1.5 servings of red meat a day appeared to have a 22 percent higher risk of breast cancer than those who ate just one serving a day. Each additional daily serving of red meat seemed to increase the risk of breast cancer another 13 percent, Farvid said.

But poultry made a great substitute. Swapping one serving a day of red meat for a serving of fowl reduced the risk of breast cancer by 17 percent overall and by 24 percent among postmenopausal women, the researchers said.

“Decreasing consumption of red meat and replacing it with other healthy dietary sources of protein, such as chicken, turkey, fish, beans, lentils, peas and nuts, may have important public health implications,” Farvid said, reducing not only the risk of breast cancer but also “other chronic diseases, such as coronary heart disease, stroke, diabetes and other kind of cancers, as well.”

Because this is a so-called observational study, it doesn't prove that more red meat increases breast cancer risk – it just shows an association. Also, the reasons for the apparent red meat-breast cancer connection aren't clear.

Cancer-causing “byproducts created during high-temperature cooking of red meat” may be to blame, Farvid said. Another possibility is the hormones used to increase growth of beef cattle (we'd bet money on this one). Farvid also cites “food preservatives such as nitrate and nitrite in processed meat,” which “can also be associated with elevated risk of breast cancer.” The increased risk also could be because red meat contains more saturated fat, which can raise levels of cholesterol and hormones that can cause tumors.

And if you think you can wait to stop eating so many of those Double-Doubles until you're postmenopausal – sorry. The researchers found that eating more red meat in younger years can be a risk factor for developing the disease in later life.

The report was published online June 10 in the British Medical Journal.

For the study, Farvid and her colleagues collected data on almost 89,000 premenopausal women, aged 26 to 45, who took part in the Nurses' Health Study II. Participants completed a questionnaire on diet in 1991, 1995, 1999, 2003 and 2007.

The women were asked about daily consumption of unprocessed red meat, such as beef, pork, lamb and hamburger, as well as 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.

Over 20 years of followup, 2,830 women developed breast cancer, according to the study. 

To try to determine red meat's exact role in the risk for breast cancer, the researchers also factored in differences in height, weight, race, family history of breast cancer, history of benign breast disease, smoking, menopausal status and hormone and oral contraceptive use. They also took into account the participants' diets when they were teens.

Of course, there are numerous other “lifestyle factors” that could have contributed to the outcome. Some scientists argue that women who eat less red meat tend to have more healthful lifestyles overall. People who eat more red meat have been found to be generally unhealthier: they are more likely to be overweight, smoke and not exercise.

Egg salad sandwich, anyone?

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