WASHINGTON (Reuters) - By eating walnuts, women could reduce their risk of breast cancer, researchers said on Tuesday.

Researchers at Marshall University School of Medicine in Huntington, West Virginia, found that lab mice bred to develop breast cancer had a significantly lower risk of breast cancer if fed the human equivalent of a handful of walnuts a day.

"Walnuts are better than cookies, french fries or potato chips when you need a snack," Elaine Hardman, one of the researchers working on the study, said in a statement.

"We know that a healthy diet overall prevents all manner of chronic diseases," she said.

Hardman said while the study was done with laboratory animals, likely the same mechanism would be at work in people.

"Walnuts contain multiple ingredients that, individually, have been shown to slow cancer growth including omega-3 fatty acids, antioxidants and phytosterols," Hardman's team wrote in a summary presented at the American Association for Cancer Research's annual meeting in Denver.

The researchers used specially bred mice that normally always develop breast cancer. Half got the human equivalent of two ounces of walnuts per day and half got a normal diet.

The mice eating the walnuts had fewer and smaller breast tumors and those that did get them got them later than the other mice.

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

"It is clear that walnuts contribute to a healthy diet that can reduce breast cancer."

The study adds to evidence that omega-3 fatty acids can provide a range of health benefits, from preventing heart disease to lowering cancer risks.