Washington, Sep 2 (IANS): A modest amount of walnuts in diet knocked off much of the breast cancer risk among mice.

Elaine Hardman from Marshall University's School of Medicine, compared the outcome of a typical diet and a diet containing walnuts in the lifespan of mice.

The group whose diet included walnut developed breast cancer at less than half the rate of the group with typical diet, Hardman said.

Besides, the number of tumours and their sizes were significantly smaller, the journal Nutrition and Cancer reports.

?These reductions are particularly important when you consider that the mice were genetically programmed to develop cancer at a high rate,? a Marshall University statement reported Hardman as saying.

?We were able to reduce the risk for cancer even in the presence of a pre-existing genetic mutation,? Hardman added.

Genome News Network had reported in 2004: "Scientists have developed a new technique for growing human breast tissues in living mice. The restructured mice may serve as the best experimental model yet for studying human breast cancer."

Using genetic analysis, the Marshall study found that walnut-containing diet changed the activity of multiple genes 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 tumour growth decreased when dietary vitamin E increased. Hardman said the findings highlight the vital role diet plays in health.