A new study published in the journal of Cancer Investigation, found that eating a modest amount of walnuts can protect against prostate cancer.
Researchers injected immune-deficient mice with human prostate cancer cells. Within three to four weeks, tumors typically start to grow in a large number of these mice, who were fed a walnut-enriched diet
in comparison to a control group who were fed with a non-walnut diet.
The comparative amount of Walnuts to a human diet, fed to the mice, consisted of approx 2 ounces per day.
Three of 16 mice (18 percent) eating the walnut-enriched diet developed prostate tumors, compared with 14 of 32 mice (44 percent) on the non-walnut control diet. Also of note, the final average tumor size in the walnut-fed animals was roughly one-fourth the average size of the prostate tumors that developed in the mice eating the control diet.
“We found the results to be stunning because there were so few tumors in animals consuming the walnuts and these tumors grew much more slowly than in the other animals,” said study senior author Russel Reiter, Ph.D., professor of cellular and structural biology at the Health Science Center. “We were absolutely surprised by how highly effective the walnut diet was in terms of inhibition of human prostate cancer.”
A previous study also described in the journal of Cancer investigation determined that a Walnut enriched diet had a significant impact on breast cancer.
The study, led by Elaine Hardman, Ph.D., of Marshall’s Joan C. Edwards School of Medicine, 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 about 2 ounces a day for humans.
Hardman said 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 significantly smaller.
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 showed that increases in omega 3 fatty acids did not fully account for the anti-cancer effect, and found that tumor growth decreased when dietary vitamin E increased.
Hardman said the findings highlight the vital 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,” she said.
Russel J. Reiter, Dun-Xian Tan, Lucien C. Manchester, Ahmet Korkmaz, Lorena Fuentes-Broto, W. Elaine Hardman, Sergio A. Rosales-Corral, Wenbo Qi. A Walnut-Enriched Diet Reduces the Growth of LNCaP Human Prostate Cancer Xenografts in Nude Mice. Cancer Investigation, 2013; 31 (6): 365 DOI: 10.3109/07357907.2013.800095