We've all been told for years about the dangers of too much tanning. But now experts are saying that too little sun can cause serious problems.

A few decades ago, holidaymakers thought nothing of basking for hours in the hottest part of the day in order to acquire a mahogany tan. Sun lotions, if used at all, were applied purely to promote faster bronzing. Then the bad news about skin cancer sent many people scurrying for shade.

Now, some say that we have overdone the caution, as increasing numbers of people are suffering from a deficiency of vitamin D, 80 per cent of which we obtain from the sun.

SunSmart, the UK's skin cancer prevention campaign, used to counsel that everyone must stay in the shade between 11am and 3pm. It has now altered that advice to the much more vague “spend time in the shade between 11am and 3pm”. “We are an evidence-based campaign that is constantly responding to new findings,” says SunSmart's campaign manager Rebecca Russell. Ongoing research shows there are lots of benefits of sun exposure and negative health outcomes linked to vitamin D deficiency.

“However, it is also true that excessive sun exposure is directly linked to skin cancer. This is increasing and we expect the warmer weather and higher UV levels we are experiencing to have a direct effect on the number of skin cancer cases.”

Tanning may look attractive but it is also a bad sign, says Nina Goad of the skin disease research charity, the British Skin Foundation. “While many people associate a tan with looking healthy, a tan is actually a sign that our skin is already harmed by UV radiation and is trying to defend itself against further damage,” she says. “This kind of damage can in turn increase your risk of developing skin cancer.”

Vitamin D is essential for cell growth, but it is hard to get all we need from the diet because it is present in relatively few foods. Sunlight enables the body to synthesise vitamin D but this can only occur in the summer because the UK's latitude means the sun is too far away during winter to provoke the chemical reaction that produces the vitamin.

D-days

There are certainly signs that vitamin D deficiency is increasing. One study of women in the final month of pregnancy who were living in the South-east – the sunniest part of the country – showed 50 per cent had inadequate supplies. Other research suggests that 15 to 20 per cent of adults in the UK had sufficiently low vitamin D stores to be very likely to experience pains and muscle aches.

What's more, experts have found that some groups are at higher risk of deficiency, such as older people who make vitamin D less efficiently than young people; those with dark skins whose pigment blocks the absorption of UV radiation; the housebound; and those who cover up for health, cultural or religious reasons. Just to add to the confusion, smothering yourself in sunscreen can add to the problem, as anything stronger than factor 8 blocks the skin's ability to make vitamin D.

“There is a major unrecognised epidemic of vitamin D deficiency in the US and UK adult population,” says Michael Holick, Professor of Medicine, Physiology and Biophysics at Boston University Medical Centre.

“Chronic deficiency has subtle and insidious consequences for health and wellbeing – in particular for older people. For example, 40 to 60 per cent of people with the musculoskeletal disorder, fibromyalgia, are deficient in vitamin D, as are 63 per cent of women with osteoporosis,” he says.

As well as osteoporosis, vitamin D deficiency has been linked to a higher risk of some cancers, notably prostate, breast and bowel – though the evidence is not yet conclusive – and to an increased risk of developing both type 1 and type 2 diabetes.

However, anybody tempted to boost their vitamin D levels by prolonged sun exposure should bear in mind that the dangers we've been told sunbathing can bring do still exist. Each year, more than 75,000 cases of skin cancer are registered in the UK, with more than 1,700 people dying from malignant melanoma.

“Up to 80 per cent of skin cancers could be prevented by being sun smart,” says Rebecca.

The amount of exposure you need to obtain adequate levels of vitamin D depends on your skin type (fair-skinned people synthesise the vitamin more easily than those with dark skins), the season of the year and the latitude. “What is certain is that the time in the sun required to tank up your vitamin D levels is much less than the time it takes to tan or burn,” says Rebecca.

Dr Peter Selby, a consultant physician specialising in bone disease at Manchester Royal Infirmary, offers this advice: “By exposing your face, hands and forearms to the sun without burning for 20 minutes three times a week, when your shadow is shorter than your height, you will get enough of the right rays to make sufficient vitamin D to see you through the year.”

Brownie points: Stay safe in the sun by using some sun sense

• Avoid getting burnt. This is possibly the most important single piece of advice for sun lovers, according to the experts. “Burning can greatly increase your chances of developing skin cancer and the effect is cumulative, so the fewer times you burn, the better,” says Rebecca Russell of SunSmart.
• Sunscreens should be treated as a medical necessity rather than a cosmetic luxury but it's important not to over-rely on them. “Don't use sunscreen in the belief that you can stay out longer in the sun,” says Nina Goad of the British Skin Foundation. “Treat it more as a way of protecting your skin when sun exposure is unavoidable.”
• People in the UK should wear sunscreen from March to the end of October. So says Dr Nick Lowe, consultant dermatologist at the Cranley Clinic, London, and professor of dermatology at UCLA School of Medicine in California. His advice is to use it on the face, arms, ears, neck and exposed parts of the upper chest.
• Choose a waterproof, broad-spectrum lotion or cream. This protects against UVB and UVA rays. Always apply it generously, rub it in lightly 30 minutes before going into the sun and reapply every couple of hours. “Factor 15+ offers the best balance between protection and price,” says Rebecca. “Anything over that will only increase the protection level by a small amount.”

Store sunscreens out of direct sunlight. Also use before the sell-by date as the active ingredient can degrade after about two years. In a survey of sunscreens carried out by Which? magazine last year, factor 15 products by Ambre Solaire, Lancôme, L'Oréal and Piz Buin came out best.

Older people should take as much care of their skins as anybody else, counsels Dr Lowe. “There is a mistaken belief that there is no point in protecting your skin if the damage has been done. But this is absolutely not the case and you should be particularly careful if you have fair skin or a family history of skin cancers.”

And if you're worried about your skin, the resounding advice is: see an expert. Treatment is more straightforward and survival rates higher when skin cancer is diagnosed early. So, if you notice new moles or an old mole changes shape, grows, bleeds or becomes itchy for no reason, then arrange to see a dermatologist. Says Dr Lowe: “Studies show that dermatologists are more accurate at diagnosing skin cancers than doctors in primary care and other physicians.”

Further information, see:

• The Cancer Research SunSmart site
• The British Skin Foundation site