Girls who enjoy a peanut butter spread on their morning toast may have healthier breast health later in life.

A study conducted by the Washington University School of Medicine and Harvard found that girls who regularly ate peanuts between the ages of nine and 15 were 39 percent less likely to develop benign breast diseases by age 30 than those who shunned the nuts, a WU press release reported.

Benign breast diseases are usually not dangerous themselves, but they do increase the risk of breast cancer in later life.

"These findings suggest that peanut butter could help reduce the risk of breast cancer in women," senior author Graham Colditz, MD, DrPH, associate director for cancer prevention and control at Siteman Cancer Center at Barnes-Jewish Hospital  and Washington University School of Medicine, said.

The researchers looked at the medical histories of 9,039 U.S. girls who participated in the Growing Up Today Study that spanned from 1996 to 2001, and then again from 2005 to 2010. Participants between the ages of 18 to 30 were asked to report if they were diagnosed with a benign breast disease that was confirmed through a biopsy.

The team found that the women who at peanut butter or nuts at least twice a week lowered their risk of developing the cancer-causing diseases by 39 percent than people who never touched the legumes.

A decreased risk of cancer were also found in girls who regularly ate "beans, lentils, soybeans and corn," but these items tended to be consumed less frequently so the link was not as strong as it was in peanuts.

Past studies have noticed a lower rate of benign breast disease in women who ate peanuts, but the study participants were asked to remember their eating habits when they were in high-school, which for some was fairly far back. The study is the first of its kind to use adolescents.