Laboratory Study Finds Walnut Consumption Slows Cancer Growth

Walnuts have at least three components that could account for their cancer-slowing effect, Hardman said. They are high in omega-3 fatty acids, which have been shown to slow cancer growth.

26/09/08 Snack-sized quantities of walnuts slow cancer growth in mice, reports a Marshall University pilot study published in the current issue of the peer-reviewed journal Nutrition and Cancer.

Researcher W. Elaine Hardman, Ph.D., of Marshall's Joan C. Edwards School of Medicine said the study was designed to determine whether mice that got part of their calories by eating walnuts had slower breast cancer growth than a group eating a diet more typical of the American diet.

"When we fed the mice the walnuts, the growth rate of the tumors they had was dramatically suppressed," Hardman said.

The mice ate a diet in which 18.5 percent of the daily calories -- the equivalent of two servings for humans -- came from walnuts. Tumors in the walnut-fed group took twice as long to double in size as tumors in the control group, the article reports. The study is believed to be the first to look at the impact of walnut consumption on cancer growth.

"It's always very good to find something that will slow the growth of tumors without being toxic chemotherapy," said Hardman, who has spent 15 years studying the role of diet in cancer.

Walnuts have at least three components that could account for their cancer-slowing effect, Hardman said. They are high in omega-3 fatty acids, which have been shown to slow cancer growth. They also include antioxidants and components called phytosterols, both of which have shown cancer-slowing effects in other studies.

While the pilot study was only designed to determine whether -- not why -- walnuts had a tumor-suppressing effect, Hardman said research as a whole is suggesting that Americans need to get more of their fat calories from fats rich in omega-3 fatty acids and fewer fat calories from saturated fat or foods high in omega-6 fatty acids.

In addition to walnuts, other good sources of omega-3 fatty acids are fish and canola and flaxseed oils, she said.

Medicine is increasingly looking at dietary changes as a way to reduce cancer, Hardman said.

"We're beginning to understand that your diet probably contributes to one-third to two-thirds of all cancers that develop, and making dietary changes to prevent cancer could do more to reduce the deaths from cancer than chemotherapy to treat cancer," she said.

"Changing our habits to reduce our risk not only of cancer but also of other chronic diseases, such as heart disease and diabetes, could reduce our health costs that are eating us up and provide better lives for a lot of people," she said. "I think in the future -- and probably the near future -- our diet, and making dietary changes, is going to become the biggest weapon for fighting cancer."

The project was funded through grants from the American Institute for Cancer Research and the California Walnut Commission, neither of which had input on the interpretation or reporting of the findings.