A modest amount of walnuts in the diet significantly drops the risk of breast cancer in mice, a new study found.

Study by Elaine Hardman, Ph.D., of Marshall's Joan C. Edwards School of Medicine, compared the effects of diet containing walnuts across the lifespan of mice to explore how walnuts affect breast cancer.

It was published in the journal Nutrition and Cancer.

Researchers found that the group of mice eating a diet that included walnuts developed less than half the rate of breast cancer than the group with the typical diet. The amount of walnuts in the test diet equates to about two ounces a day for humans.

“These reductions are particularly important when you consider that the mice were genetically programmed to develop cancer at a high rate,” Hardman said. “We were able to reduce the risk for cancer even in the presence of a preexisting genetic mutation.”

Using genetic analysis, Marshall Study found that the walnut-containing diet changed the activity of multiple genes that are relevant to breast cancer in both mice and humans.

An increase in omega 3 fatty acids did not fully account for the anti-cancer effect, the study found. Tumor growth decreased when dietary vitamin E increased.

Walnuts are rich source of energy and contain many nutrients, minerals, antioxidants and vitamins that are essential. They are rich in monounsaturated fatty acids.

Hardman said the findings highlight the vital role diet plays in health.

“The results of this study indicate that increased consumption of walnut could be part of a healthy diet and reduce risk for cancer in future generations,” she said.