A daily handful of walnuts may stave off prostate cancer, according to new research. Scientists have found diets rich in the nut, or its oil, slowed tumour growth in mice. They also reduced cholesterol and increased sensitivity to the hormone insulin which helps prevent diabetes. Walnuts are a ‘superfood’ naturally high in a host of health boosting chemicals, including omega-3 fatty acids, and have already been shown to protect against breast cancer and heart disease. The latest findings showed they cut levels of the hormone IGF-1, which has been implicated in both prostate and breast cancer. Dr Paul Davis, of the University of California at Davis, said: ‘For years, the United States government has been on a crusade against fat, and I think it has been to our detriment. ‘Walnuts are a perfect example. While they are high in fat, their fat does not drive prostate cancer growth. ‘In fact, walnuts do just the opposite when fed to mice.’ Some 35,000 Britons are diagnosed with it each year, and 10,000 die. The new study, published in the Journal of Medicinal Food, was aimed at finding out if the beneficial properties were unique to walnuts, or whether it was a particular ingredient such as omega-3 fatty acids found in other foods. The mice were fed whole walnuts, walnut oil or a walnut like fat for 18 weeks. While the two former reduced cholesterol and slowed prostate cancer growth, in contrast, the latter did not have these effects, proving other nut components caused the improvements. Dr Davis said: ‘We showed it is not the omega-3s by themselves, though, it could be a combination of the omega-3s with whatever else is in the walnut oil. ‘It is becoming increasingly clear in nutrition it is never going to be just one thing, it is always a combination.’ While the study did not pinpoint which combination of compounds in walnuts slows cancer growth, it did rule out fibre, zinc, magnesium and selenium. In addition, the research demonstrated walnuts modulate several mechanisms associated with cancer growth.