Eating walnuts may provide women with essential omega-3 fatty acids, antioxidants and phytosterols that can help reduce the risk of breast cancer, according to the results of an animal study presented today at the American Association for Cancer Research's 100th annual meeting in Denver.

"Walnuts can be considered a valuable part of a healthy diet," principal investigator Dr. Elaine Hardman of Marshall University School of Medicine in Huntington, West Virginia, told Reuters Health. "When you need or want a snack, a few walnuts would be a far better choice than cookies, chips or soda," she said.

Hardman and her colleagues fed genetically altered mice a diet containing what they estimated was the human equivalent of two ounces of walnuts per day. A separate group of mice were fed another diet without walnuts.

Tests showed that walnut consumption significantly decreased the number of mice with at least one tumor, the number of glands containing a tumor and the size of the tumors.

"These laboratory mice typically have 100 percent tumor incidence at five months; walnut consumption delayed those tumors by at least three weeks," Hardman noted in a meeting statement.

Further analysis showed that the walnut-rich diet boosted omega-3 fatty acid concentrations, which contributed to the decline in tumor occurrence, but other components of the walnut contributed as well, the researchers say.

"With dietary interventions you see multiple mechanisms when working with the whole food," Hardman explained. "It is clear that walnuts contribute to a healthy diet that can reduce breast cancer."