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Small red tomatoes nestling among green peppers, sliced carrots and spring onions not only brighten up a salad but also give some protection against a wide variety of cancers. They have other more mundane properties as well. Holidaymakers in France and Spain may be less likely to suffer sunburn and prematurely aged skin if they eat tomatoes, rich in lycopene, and other fruits and vegetables rich in carotenoids.

Carotenoids are the micronutrients, mainly dark yellow or red, that give some fruits and vegetables their colour and health-giving powers. Tomato juice or ketchup with the fish and salad won't in any way replace a high-factor sunscreen, but it offers some protective action against inflammation, premature skin ageing, photo-sensitivity disorders and some skin cancers. The carotenoids in tomatoes, peppers and pomegranates once eaten are later widely distributed in the epidermal and dermal layers of the skin.

In the skin they help to absorb the light, act as antioxidants and have an anti-inflammatory response to sunburn. They act by increasing the circulation of the blood to the skin and thus its nutrition. The better skin nutrition the less its scaliness and roughness, and more improved its thickness and hydration.

Scientists attending the First International Congress on Nutrition and Cancer in Turkey last week discussed the effect of nutrition on skin health as well as on malignancies. The study of nutrition is increasingly moving from a focus on diet to food science. It is now accepted that the diet enjoyed by those living in the Far East or the Mediterranean countries has advantages over typical Western fare and contributes to a longer life. Scientists can now explain the biochemical mechanism and demonstrate how the micronutrients in the diet can interfere with the body's cellular pathways to help to prevent cancer.

Before discussing the complex cellular pathways that determine how diet is involved in between one and two thirds of cancers, Professor Walter Willett, of Harvard University, outlined the changes to lifestyle that help to reduce their incidence. He advised that everyone should take a great deal more exercise, should lose weight and increase their intake of fruit and vegetables.

Willett suggested that this would be especially useful in reducing cancers of the head and neck, such as those of the mouth, throat and oesophagus as well as those of the gastrointestinal tract and, above all, prostate, breast and ovaries. Willett would have us eating apples, as fresh as possible, every day and tomatoes - the star food of the conference - onions and garlic. And drinking pomegranate juice - also star-rated.

To keep the lower gastrointestinal tract, the colon and rectum healthy, he recommended a selection of fruit and vegetables to maintain adequate levels of betacarotene, vitamin C and vitamin E, as well as folic acid. One speaker spoke of the association of high alcohol consumption with a low folic acid intake and the high incidence of colorectal cancer

Betacarotene has been the subject of controversy because of its failure to reduce the incidence of lung cancer in smokers. In fact, betacarotene when taken alone without vitamin C and E was shown to increase the liability to develop lung cancer. Conversely, when betacarotene was taken with vitamin C and E its influence was equivocal. It was recommended that those people who take betacarotene, which does have a beneficial effect on other tissues, should also take adequate vitamin C and E.

The influence of vitamin E and C on the value of betacarotene was only one example of the power of synergy. Years ago when visiting a food research institute my guide pulled up a carrot from the earth and ate it. She explained that carrots, unlike betacarotene tablets, contain a score or more of micronutrients, as well as betacarotene, and the power of the carrot relies on the interaction between them.

Lycopene, a powerful antioxidant that affects inflammatory and other cellular pathways, received universal approval. Its power also benefits from a synergistic effect. When lycopene is extracted from tomatoes, rather than from other substances, it contains two other naturally occurring carotenoids. These provide the necessary synergistic reaction that has an influence on a large number of other cancers, including, importantly, prostate and breast cancer.

Lyc-O-mato is a lycopene supplement that is made from specially modified tomatoes and provides lycopene and the other two synergistic carotenoids. Everyone should take more apples, tomatoes and pomegranate juice. They shouldn't forget ketchup, tomato juice, tomato sauce and paste. The lycopene in cooked tomatoes is more available than in the raw variety. Lyc-O-mato supplement is available in Boots and other chemists. It will make it safer for you to wander around in the early morning or afternoon sun as you lay in your store of vitamin D for the winter.

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