It’s still very early research, but a study done on mice has shown that walnuts could help reduce breast cancer.

A new study - funded by the American Institute for Cancer Research (AICR) and published in the journal Nutrition and Cancer - shows that the risk of breast cancer dropped significantly in mice when their regular diet included just a modest amount of walnuts throughout their life.

The study compared the effects of a typical diet to that of a diet containing walnuts across the lifespan. Some of the mice were even given walnuts in the womb through their mother.

"This is an animal study so we don't know if the findings apply to humans yet," explains Alice Bender, RD, AICR nutrition communications manager, "but it's interesting and it really tells us how whole foods such as walnuts might play a role in preventing cancer. What is already clear is if people eat more unprocessed fiber-filled foods like walnuts, vegetables, fruit, whole grains and beans, they can improve health and reduce their risk of cancer and other chronic diseases.”

The amount of walnuts in the test diet was equal to about 2 oz. a day for humans, and the best results were seen in mice whose mothers consumed walnuts and then ate the nut themselves, says W. Elaine Hardman, PhD, the study's lead investigator and associate professor at the Marshall University's Joan C. Edwards School of Medicine.

Specifically, the mice that consumed walnuts starting before birth had half the rate of breast cancer than those mice that had consumed no walnuts; and the mice that ate walnuts after weaning, had one-third fewer tumors than the mice that had no walnuts.

Despite the results, it’s not for certain whether the reduced cases of breast cancer were a result of the walnuts being added to the mice’s diets, or the resulting reduction of unhealthy fats the mice avoided because of the inclusion of the walnuts.

Hardman says other studies have clearly shown, however, that multiple ingredients in walnuts reduce the risk of cancer or slow its growth. Specifically, walnuts contain components that may slow cancer growth, including: omega 3 fatty acids, phytosterols, polyphenols, carotenoids, and vitamin E.

The findings highlight the vital role diet plays in health.

"This study really underscores the importance of routinely eating whole foods where nutrients and phytochemicals all work together for better health and cancer protection," says Bender.

The study was funded by grants from the AICR, with a matching grant from the California Walnut Commission. Neither group had any input on the study design or findings.

In related news, the California Walnut Industry is expecting a healthy crop this year, predicting the annual walnut yield to be 485,000 short tons. That’s slightly lower than last year's record-breaking crop of 503,000 short tons, but the 2011 estimate still suggests the second largest crop on record.

"We are delighted not only with the crop size but also with the high quality kernels we are expecting thanks to the mild spring and summer weather,” says California Walnut Commission Chairperson Charles Crain. “This excellent crop will help us continue to meet the growing consumer demand for nutritious walnuts both domestically and around the world."

California walnuts account for 99% of the commercial U.S. supply and 78% of world supply.

For more information on the AICR visit; for more information on the California Walnut Commission, visit