Can Girls Lower Their Breast Cancer Risk by Eating Peanut Butter?

Krista Kleczewski, Cancer Prevention and Treatment Fund

Peanut butter, a favorite food of so many kids and overwhelmed parents, may help ward off abnormal breast conditions linked to cancer, according to researchers from Harvard and Washington University School of Medicine. The study, funded by the National Institutes of Health (NIH) and the Breast Cancer Research Foundation, found that girls between the ages of 9 and 15 who regularly ate foods high in vegetable protein and fat had a significantly lower risk of developing non-cancerous (benign) breast conditions as young women than those who did not eat these foods.¹ Peanut butter, peanuts and nuts were the main sources of vegetable protein and fat in the girls’ diets.

What is Benign Breast Disease and How is it Related to Breast Cancer?

Benign breast diseases are changes in the breast that sometimes have no symptoms and sometimes can cause pain or discomfort, but are not cancerous. Some benign breast diseases increase a woman’s risk of eventually developing breast cancer only slightly, while others can increase her risks more substantially.²^,³ For example, women with simple cysts or fibrosis (scar-like tissue in the breasts) have almost the same risk of developing breast cancer as women who don’t have these benign breast conditions.⁴ However, women who have fast-growing abnormal cells, called atypical hyperplasia, are 3-4 times more likely to develop breast cancer than women with normal breasts.⁴

Peanut Butter and Benign Breast Disease

The study enrolled 9,039 girls, ages 9 to 15, and kept in touch with them for 14 years. The girls regularly reported to the researchers what they ate and drank, and whether they had been diagnosed at any point between the ages of 18 and 30 with benign breast disease. Adolescent girls who ate peanut butter or any kind of nuts three times a week or more had a nearly 40% lower chance of developing benign breast disease.

Although all the girls who ate peanut butter and nuts were less likely to develop benign breast disease, the girls who benefited the most were those who had a family history of breast cancer. This is important because, in general, benign breast disease is riskier in women with a family history of breast cancer.

Many people think of peanuts as nuts, but they are actually legumes.  For that reason, it is not surprising that the researchers found that consumption of other legumes such as beans, lentils, soybeans, as well as corn, may help shield girls from these breast conditions. Although the researchers did not study the benefits of specific types of nuts, it is believed that regular consumption of most nuts, including tree nuts, such as almonds and walnuts, provide protection against benign breast disease. At least one study in 2011 found that a diet containing walnuts slowed breast cancer tumor growth in mice; more research is needed before we will know if this is true for humans.⁵

Should All Girls Eat More Peanut Butter, Nuts, and Beans?

Although this was a large study of over 9,000 girls living in all 50 states, 95% of the girls were non-Hispanic whites, primarily from middle and upper socioeconomic backgrounds. As a result, it is impossible to say whether the study’s findings would also apply to girls from other races, and ethnicities, or to girls of lower socioeconomic backgrounds.

The study had other limitations. Because the girls filled out questionnaires about their eating habits, the researchers did not observe what the girls actually ate, or how much. This means the researchers had to rely on the girls remembering and reporting their intake accurately.

Another important question is do these foods truly protect against benign breast disease and possibly even breast cancer, or do the girls who eat them eat fewer less nutritious foods that would increase the risk of cancer? Whichever the answer, it’s a good idea—particularly if you have breast cancer in your family— to eat snacks involving peanut butter or a handful of nuts instead of less healthy alternatives like cookies, candy, or chips. Nuts and nut butter are what nutritionists call “nutrient dense” foods. They are rich in protein and nutrients, but they are also high in calories. So eat them in moderation and don’t assume that the new study means you can eat Reese’s Peanut Butter Cups to your heart’s content! They are not a nutritious snack choice! Similarly, it is best to look for low-salt and peanut butter brands without added sugar or oils. Try peanut butter with an apple or banana, peanuts low in salt, or an old classic called “Ants on a Log,” which is a stick of celery with peanut butter and raisins sprinkled on top.

Spread the news, and spread the peanut butter (in moderation, of course)!