FRIDAY, Sept. 27 (HealthDay News) -- Eating peanut butter regularly as a preteen and teen girl appears to decrease the risk of developing benign breast disease as an adult, new research has found.

Benign breast disease -- noncancerous changes in the breast tissue -- is a risk factor for breast cancer, experts agree.

The researchers followed more than 9,000 females, beginning when they were aged 9 to 15 in 1996, until 2010, when they were young women. Eating peanut butter three days a week reduced the risk of developing benign breast disease by 39 percent, said Dr. Graham Colditz, senior study author.

"I think this gives us enormous hope there are strategies we could be following to help prevent breast cancer that we haven't capitalized on yet," said Colditz, the associate director for cancer prevention and control at the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine, in St. Louis.

The study, published online Sept. 17 in Breast Cancer Research and Treatment, was funded by the Breast Cancer Research Foundation and the U.S. National Institutes of Health.

Benign breast disease is fairly common, and a known risk factor for breast cancer, Colditz said. Before menopause, "about one in four women have a benign lesion, confirmed by biopsy," he said. "It's very clear there is a strong link between the benign lesion and the subsequent risk of invasive breast cancer."

Depending on the characteristics of the benign lesion, he said, benign breast disease could increase breast cancer risk by threefold.

The study participants were part of a long-term, ongoing study on the health effects of diet and exercise in young people. They filled out questionnaires about their diet annually from 1996 until 2001, then four more times until 2010. They also reported if they had been diagnosed with benign breast disease. In all, 112 women said they had.

The researchers looked at foods with vegetable protein and vegetable fats, then focused on individual foods, including peanut butter, peanuts or other nuts, beans and corn.

A daily serving of any of these foods was linked with a 68 percent reduced risk of benign breast disease. At age 14, a daily serving of any of those foods was linked with a 66 percent lower risk of benign breast disease, and girls who had about three servings a week of peanut butter had a 39 percent lower risk.

The researchers found a link between eating peanut butter and lower breast disease risk, not a cause-and-effect relationship, and Colditz said he can't explain yet why the peanut butter seems protective.

"It could well be the protein," he said. In previous studies, the researchers have looked at other factors of a healthy diet, such as milk consumption, and their role in breast health. The peanut butter finding, he said, is strong, even when taking into account an overall healthy diet. "It's not something we can make go away," he said.

For now, Colditz said, the take-home message is for teens and preteens to substitute peanuts and peanut butter for less-healthy snacks such as cookies.

Another expert who reviewed the findings said the study is well done.

Dr. Steven Chen, an associate clinical professor of breast and endocrine surgery at the City of Hope Comprehensive Cancer Center, in Duarte, Calif., said that while lowering benign breast disease does lower breast cancer risk, many other factors increase breast cancer risk besides benign breast disease.

"It's always good to lower any risk [of breast cancer] you can, but whether peanut butter intake will have a major impact on developing breast cancer down the line, only time will tell," Chen said.

As for how to explain the link? "It's hard to say at this point," Chen said, adding that in countries where less meat is eaten, less breast cancer risk is reported. Based on the study findings, he said, teen girls and preteens "shouldn't avoid peanut butter and nuts if they are not allergic." Getting some protein through vegetables, which was also looked at in the study, is a good idea, too, he added.

More information

To learn more about benign breast conditions, visit the American Cancer Society.