Breast Cancer Risk Decreases When Walnuts Are Included in Diet

The risk of breast cancer dropped significantly in lab mice when their regular diet included a small amount of walnut, researchers recently reported.

The study, led by Elaine Hardman, PhD, from Marshall’s Joan C. Edwards School of Medicine (Huntington, WV, USA), compared the effects of a typical diet and a diet containing walnuts across the lifespan: through the mother from conception through weaning, and then through eating the food directly. The amount of walnut in the test diet equates to approximately 2 ounces per day for humans.

Dr. Hardman stated that during the study period, the group whose diet included walnut at both stages developed breast cancer at less than half the rate of the group with the typical diet. In addition, the number of tumors and their sizes were considerably smaller. “These reductions are particularly important when you consider that the mice were genetically programmed to develop cancer at a high rate,” Dr. Hardman said. “We were able to reduce the risk for cancer even in the presence of a preexisting genetic mutation.”

The article, published online August 11, 2011, in the journal Nutrition and Cancer noted that dietary modification studies do not show whether benefits result from what is added to a diet or what is removed. In this instance, adding healthy fat and other components meant that unhealthy fat was reduced to keep total dietary fat balanced in the mice. Dr. Hardman reported that other studies have distinctly shown, however, that multiple ingredients in walnuts reduce the risk of cancer or slow its growth.

Using genetic analysis, the 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. Other testing revealed that increases in omega 3 fatty acids did not fully account for the anticancer effect, and found that tumor growth decreased when dietary vitamin E increased.

Dr. Hardman noted that the findings emphasize the key role diet plays in health. “Food is important medicine in our diet,” she said. “What we put into our bodies makes a big difference--it determines how the body functions, our reaction to illness and health. The simple stuff really works: eat right, get off the couch, and turn off the TV. 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.”

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Marshall’s Joan C. Edwards School of Medicine