Hooray! The sun is good for you

Despite the poor British summer we're having, the latest research suggests that too many people stay indoors on hot, sunny days following warnings about sunbathing and skin cancer.

The research, from Australia, has revealed that attempts to encourage people to protect themselves against the sun's rays have helped raise cancer awareness but also brought damaging side effects. One in four women in Australia - the skin cancer capital of the world - is now deficient in vitamin D as a result of too little sunlight.

Sunshine provides around 90 per cent of the vitamin D the body needs to protect against frail bones, weak muscles and, according to some experts, deadly forms of cancer.

Other research also suggests that moderate exposure to the sun can help ward off depression, combat certain skin diseases and even increase the chances of surviving a heart attack. "For people in Britain, the main source of vitamin D is still sunlight, and you need a certain amount of it to provide for normal body function," says Dr Tim Key from Cancer Research UK. "Some sunlight is essential, so you don't want to stay indoors all the time in order to avoid skin cancer."

For most people, it's estimated that five or 10 minutes a day in the sunshine are enough to top up vitamin D reserves to the required levels. This could be just walking to work, or taking a lunchtime stroll.

Food sources of vitamin D include oily fish such as herring or mackerel, fortified cereals and some dairy products. But you would have to eat at least half-a-pound of fish or 10 eggs every day to get the same levels of the vitamin as the sun provides.

Experts insist that protection against the sun remains the most important safety message for summer. But what are the potential health benefits of limited exposure to its rays?

Cancer

One of the most controversial current theories is that while exposure to the sun undoubtedly increases the risk of skin cancer, it may also protect against breast, bowel and prostate cancers.

Earlier this year, experts at the Boston University School of Medicine in the US revealed they had found an enzyme that helps vitamin D stop these cancer cells proliferating. If the body takes in too little vitamin D, the enzyme is not activated. They believe this may help to explain why people in colder northern climates have a higher risk of dying from these cancers. But some British experts remain unconvinced. Dr Tim Key says: "The data is not good enough to draw strong conclusions."

Heart disease

If you have a heart attack in the summer rather than winter, your chances of survival are much greater. That's because when you are cold your arteries constrict and your blood pressure rises, so your heart has to work harder. A study of 11,000 people by researchers from Greater Glasgow Health Board showed that heart attack victims are 20 per cent more likely to survive if they fall ill in the summer rather than the winter.

Psorasis

Psoriasis is a debilitating and incurable skin condition that affects an estimated two to three per cent of the population. Yet many people find it is improved by exposure to the sun. This is because of the healing effects of the sun's UVB rays. But doctors stress sufferers should still use a highfactor sun cream or run the risk of burning, which can aggravate the condition.

Depression

Seasonal Affective Disorder (Sad) - where dark mornings and nights trigger increased depression - is now a recognised medical condition. In summer, when the sun shines and the days are long, the symptoms of Sad largely disappear because sunlight triggers the release of moodaltering chemicals in the brain. Many Sad sufferers now use light therapy - where they expose themselves to "false" sunlight during the winter months - to get through their depression.

Schizophrenia

Some scientists now believe that a lack of sunlight during pregnancy may increase the risk of the offspring developing schizophrenia later in life. Experts at the Queensland Centre of Schizophrenia Research in Brisbane, Australia, revealed last year that inadequate sunshine could alter the development of a child's brain in the womb because of a reduction in vitamin D levels. The finding may explain why in Europe and the US, people with schizophrenia are more likely to have been born in the spring.

Hip fractures

Fractured hips are one of the most common conditions in people with osteoporosis, a crippling bone disease that affects one in three women in the UK and one in eight men. Yet research shows an extra dose of sunshine could help reduce the risk by boosting levels of vitamin D, vital for the protection of bones in old age. The vitamin works by helping the body to absorb calcium, which increases bone density.