As Hippocrates, the famous Greek physician of the 5th century BC, once said, "Let food be your medicine and medicine be your food." This advice seems particularly apt today in light of the barrage of scientific reports that say certain foods, consumed regularly, can promote health and even prevent chronic diseases. Quentin Cooper talks to Dr Gary Williamson from the Institute of Food Research - he and his team have created a "super broccoli" with higher levels of anti-carcinogen components-about the phytochemicals in our diet and the mechanisms by which they fight illnesses such as cancer and heart disease. Producer John Watkins. E-MAIL: material.world@bbc.co.uk