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Sunny side up
Sunshine is good for you… Barbara Rowlands examines a revolution in scientific attitudes about exposure to ultraviolet rays
For years we’ve been told to keep out of the sun. Cool, pale and pasty was healthy; hot, bothered and tanned was something to be worried about. If you must go out, we were warned, arm yourself with factor 30 and a wide–brimmed hat.
But scientists are now telling us that sunshine does us a power of good – there is mounting evidence that high levels of vitamin D, produced by skin exposed to sunshine, can protect us against a range of diseases and that covering up can be positively bad for you.
We produce the vitamin when the sun’s ultraviolet (UV) rays hit the skin. Most vitamins and minerals come from food – vitamin D is the only one we make ourselves. It’s essential for healthy skin and bones and, deprived of sunlight, bones weaken and children develop rickets. We make most vitamin D between March and October and store it, camel–like, in the fat cells, to be released slowly in winter.
Ninety per cent of what we need comes from sunlight, and while you get vitamin D from cereals, egg yolk and oily fish, you’d have to eat mounds of sardines to maintain healthy levels. Experts now say that because we live at a high latitude and lather on sunscreen, about 60 per cent of us have low levels of vitamin D.
“For many years we’ve been told not to go out in the sun and put on sunscreen,” says Dr Ann Webb, a physicist at the University of Manchester. “But if you don’t get UV exposure, you’re taking away your major source of vitamin D.”
And sunlight is now being seen as powerful protection against a huge array of diseases – diabetes (types 1 and 2), high blood pressure, multiple sclerosis and some auto–immune diseases, like rheumatoid arthritis. Low levels are linked to depression and, most importantly, it protects us against 16 cancers, particularly the most common ones – prostate, ovarian, lung and bowel.
In one study the risk of prostate cancer was halved in men exposed to the sun for around 20 hours a week, and one published in 2006 showed that high levels of vitamin D translated into a 50 per cent lower risk of breast cancer. Another showed that teenagers exposed to plenty of sunshine were 25 to 45 per cent less likely to develop it. The latest research published in May showed that women with low levels of vitamin D were much more likely to die of breast cancer or for it to spread than women with high levels.
Strictly speaking, vitamin D is a hormone and its job is to regulate our cells. It influences how they mature, controls the absorption of calcium, and triggers cell death. It alters growth, and regulates the activity of the immune system. When it comes to cancer, it stimulates the release of chemicals which put a brake on the uncontrollable division of cancer cells and it may slow down the progress of cancer.
Graham Bentham, Professor of Environmental Sciences at the University of East Anglia, says: “We began to see a link between vitamin D and osteoporosis and falls, but there is accumulating evidence that low levels of vitamin D may increase the risk of some cancers and some auto–immune diseases. The levels many of us have might be fine for avoiding rickets but may be insufficient to get these protective benefits.”
Set against all this good news is the fact that too much sunlight can cause skin cancer and that the number of people with the cancer in the UK has quadrupled since the Seventies.
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