New findings published in Nutrition and Cancer report that consuming walnuts slowed both the development and growth of breast cancer tumors in mice. Considering one in eight women in the United States will develop invasive breast cancer in the course of their life[1], these findings are extremely important and provide deeper insight into choices we can make in our lives to help fight cancer and other chronic diseases.

According to Elaine Hardman, Ph.D., professor at Marshall University’s Joan C. Edwards School of Medicine, who led the research, “We think now that diet can prevent 30 to 60 percent of all cancers.  The healthy diet that we should be eating is what we know is healthy – a lot of fresh fruits and vegetables, whole grains and nuts.  Walnuts can be an important component of that diet.”

Dr. Hardman’s research looked at the effects of a diet containing a modest amount of walnuts – the equivalent of 2 ounces for humans daily – across the lifespan of the mice.  The study group whose diet included walnuts at both stages (through the mother from conception through weaning and then through eating the food directly) developed breast cancer at less than half the rate of the control group with the corn oil diet.  In addition, the number of tumors and the sizes of the tumors were significantly smaller.

“Using genetic analysis, we found that the walnut-containing diet changed the activity of multiple genes that are relevant to breast cancer in both mice and humans,” said Dr. Hardman.  In previous research with mice, Hardman’s lab found consumption of walnuts slowed the growth of implanted breast cancers.[2]

Dr. Hardman believes that the whole walnut, not just one element of the walnut, provides the benefit against cancer.  “If I tried to strip the walnut apart, I wouldn’t see the same benefit,” states Dr. Hardman.  

“We need studies like this that look at the impact of whole foods and not just isolated nutrients.  That’s the way we eat and research suggests that’s the way healthy foods best protect us.  For example, walnuts are a nutrient dense package of protective compounds such as antioxidants, phytosterols and plant-based omega-3 fat that work in harmony,” said Karen Collins, M.S., R.D., C.D.N., nutrition advisor to the American Institute for Cancer Research.

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2 Suppression of implanted MDA-MB 231 human breast cancer growth in nude mice by dietary walnut: Nutrition and Cancer. 2008 Sept; 60 (5): 666-674