Dr. Graham Colditz, associate director for cancer prevention and control at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis, and colleagues at the Harvard Medical School in Boston, said benign breast disease, although non-cancerous, increases risk of breast cancer later in life.
The study, published in the journal Breast Cancer Research and Treatment, showed girls ages 9-15 who regularly ate peanut butter or nuts were 39 percent less likely to develop benign breast disease by age 30.
"These findings suggest that peanut butter could help reduce the risk of breast cancer in women," Colditz, the study's senior author, said in a statement.
The findings were based on the health histories of more than 9,000 U.S. girls enrolled in The Growing Up Today Study from 1996-2001. Later, from 2005-10, when the study participants were ages 18-30, they reported whether they had been diagnosed with benign breast disease that had been confirmed by breast biopsy.
The researchers found participants who ate peanut butter or nuts two times each week were 39 percent less likely to have developed benign breast disease than those who never ate them.
The study's findings suggest beans, lentils, soybeans and corn also might help prevent benign breast disease, but consumption of these foods were much lower in these girls and thus the evidence was weaker, Colditz said.