If you're planning to spend time in the sun this summer, it may be a good idea to add lots of salads to your diet.

Research finds that tomatoes, green peppers, carrots and spring onions can all offer protection against a wide variety of cancers as well as protecting against sunburn and prematurely aging skin.

Many fruits and vegetables are rich in lycopene or carotenoids, and both can provide some important health benefits.

Carotenoids are the dark yellow and red micronutrients that give many fruits and vegetables their color. They protect against inflammation, skin aging, photosensitivity and some skin cancers. The carotenoids in tomatoes, peppers and pomegranates are widely distributed in the epidermal and dermal layers of the skin after they're digested.

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.

The effect of nutrition on skin health was among the topics at last week's First International Congress on Nutrition and Cancer, held in Turkey.

The study of nutrition is expanding from strictly dietary concerns to a broader focus on food scientists, as researchers find evidence that diets common in the Far East and Mediterranean countries have important health benefits over those common in the West.

Beyond describing the effects, scientists are increasingly able to 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 outlined the changes to lifestyle that help to reduce their incidence. He advised that everyone should exercise more, lose weight and increase the intake of fruit and vegetables, The Times of London reported.

Willett suggested that this would be especially useful in reducing cancers of the head and neck, such as those of the mouth, throat and esophagus as well as those of the gastrointestinal tract and, above all, prostate, breast and ovaries.

Willett recommends eating apples, as fresh as possible, every day and tomatoes -- the star food of the conference -- as well as onions and garlic. Pomegranate juice also gets his highest rating.

To keep the lower gastrointestinal tract healthy, Willett recommended a selection of fruit and vegetables to maintain adequate levels of beta carotene, vitamin C and vitamin E, as well as folic acid.

Lycopene, a powerful antioxidant, received universal approval from researchers speaking at the conference.

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.

By the way, lycopene is more available in cooked tomatoes than in raw ones, so nutritionists say we shouldn't be afraid to put an extra dab of red sauce on the pasta. Tomato juice is also beneficial.