PBJs in childhood could protect girls from developing breast cancer later in life, according to research from the Washington University School of Medicine in St. Louis and Harvard Medical School.

The study showed that young girls with a family history of breast cancer who ate peanut butter or peanuts had a 39 percent less chance of developing benign breast disease (BBD), which often leads to breast cancer, The Guardian reports.

Peanuts were beneficial even for girls who didn't have a risky family history. One daily serving was found to lower their chances of developing lumps and other benign breast conditions by age 30.

The study began in 1996 when about 9,000 girls ages nine to 15 years old were asked to fill out questionnaires annually for five years describing their food intake. Starting in 2005, these same girls as adults were asked to report if they had been diagnosed with BBD confirmed by biopsy. After analyzing the data, the researchers concluded that the girls who consumed more vegetable fat and protein were 39 percent less likely to develop breast anomalies.

The protective effect could be due to the fact that peanuts are rich in monounsaturated (“good”) fat, protein and various vitamins and minerals. Previous studies have shown they can reduce LDL cholesterol by up to 14 percent if consumed daily. According to another study, they may decrease the risk of heart disease by 21 percent.

Peanuts have also been found to be beneficial in preventing type-2 diabetes. Women who consume peanuts and peanut butter five times a week or more have been found to have a 21 percent less chance of developing type-2 diabetes compared to those who never eat them.

Peanuts aren't actually nuts, but a legume like lentils and beans, so they contain much more protein than real nuts — up to 25 percent. They are rich in potassium, thiamine, niacin, vitamin E, phosphorus, magnesium, copper, selenium and zinc.

Sadly, Reese's Peanut Butter Cups don't count.

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