Ever since Brigitte Bardot's portrayal of a young girl who loves nude sunbathing in the 1956 blockbuster And God Created Woman, bronzed skin has stood for sexual allure and beauty as well as good health.
But while we love to get a tan, there's huge pressure to apply high factor sunscreen – or to get the bronzing without the sun with a fake tan.
Beneath this apparent orthodoxy, there's an acrimonious debate between the experts who insist that sunshine is a toxic force against which we need constant protection and those who accuse big business of promoting "sun phobia" for commercial reasons, thus putting us at risk of a vitamin deficiency that causes rickets. Who should we believe? Here's what the experts say on the pros and cons of looking tanned.
How it works
Melanin in the skin absorbs UV radiation in sunlight, thereby changing the colour and eventually the thickness of the skin. Tanning occurs when the skin is exposed to sunlight gradually. Sudden exposure of previously protected skin to strong UV rays causes burning, quickly turning a "milk bottle" into a "lobster".
Bardot's face in later life.
Some clinicians insist there is no such thing as a safe suntan and that all sun exposure causes skin cancer as well as ageing and wrinkles. However, a series of studies have discovered widespread vitamin D deficiency in cloudy Britain. And a growing number of experts say that safe sunbathing has unparalleled health benefits by boosting levels of vitamin D, "the sunshine vitamin" that's formed when bare skin is exposed to sunlight. As well as helping to build a robust immune system and strong bones, trials suggest it fights off some cancers and depression.
"A sunny holiday with plenty of opportunity for safe and careful sunbathing is excellent for everyone's health – including those with pale skins provided they are careful," says Oliver Gillie, health campaigner and author of Sunlight Robbery. "The evidence suggests that the best approach is enjoy regular sunshine throughout the year so that you don't suddenly expose your body to UV rays."
Cancer specialist Professor Tim Oliver, consultant oncologist at Barts and the London Hospital, went out in the sun every day during a recent holiday and benefited from it, he says. "The anti-sun skin cancer message and the trend for young people to play indoors rather than running around outside is creating the potential for a health crisis. We are simply not getting enough sunlight to make the Vitamin D we need to stay healthy."
Sunburn is almost universally regarded as a major risk for skin cancer. "You shouldn't throw yourself at a beach once a year and let yourself burn," says Professor Tim Oliver. "The skin cancer message is right: melanomas or tumours on the skin are found on people who have burnt in the sun, particularly when young." Emphasising this rule, new guidelines from Cancer Research UK, issued in January 2011, advise people to avoid sunburn rather than sunshine. "People should be encouraged to enjoy the sun sensibly for the right length of time," said Ed Yong, of Cancer Research UK.
How they work
UV tanning equipment mimics the spectrum of light from sunshine. "Around 90 per cent mimic UVB and UVA rays in the summer sun, with new skin-sensor technology introduced in larger chains, providing tailored UV balance, based on measurements of skin type and tone and melanin levels," says Adam Mooney, chief executive of The Tanning Shop.
Coin-operated sunbeds in unmanned salons give rise to horror stories. Kirsty McRae, 14, from Barry Island, South Wales, received first-degree burns over 70 per cent of her body after using a coin-operated bed at an unmanned high street salon in 2009. Donna Ballantyne, from Bothwell, Lanarkshire admitted using sunbeds until she "burnt my back and shoulders to the point they were sore". She suffered 19 melanomas over 10 years and died at the age of just 39 in June 2011.
Sunbeds are now much better regulated, with a ban on the under-18s and the introduction of maximum "irradiance level", roughly that of the midday sun in the Mediterranean.
Within this safe context, there is substantial evidence that moderate use of sunbeds has the same health benefits as exposure to sunshine. A recent study showed that sunbed users have the highest vitamin D levels of any group in Canada. whileanother revealed that Swedish sunbed users have fewer melanoma than non-sunbed users.
"During the winter months many of us may benefit from the UV lamps used in sunbeds," says Professor Oliver. "Because the whole body is usually exposed, a single five to 10-minute session once every six weeks should be sufficient. I doubt GPs will ever prescribe a short sunbed course, but I don't think there would be any harm if they did."
Fears that unsupervised coin-operated sunbed shops have provoked life-threatening "tanorexia" in teenagers led to a nationwide ban on under-18s from April 2011. Tanning salons which flout this law face a £20,000 fine.
How they work
Fake tan products today contain moisturiser, skin toners, anti-ageing agents and sun protection factor and are available as creams, lotions, sprays, mousses and liquids. But the market, worth around £50m in the UK, still depends on DHA, the protein that turns apples brown when cut in half.
Most female celebrities have been judged and found guilty of orange fake tan disasters – including in the past 12 months: Cheryl Cole, Patsy Kensit and Kelly Brook.
Today it's relatively simple to get a healthy streak-free, sun-kissed look. "Use a gradual tan if you have a light skin tone, a spray or mousse for a medium skin tone and a bronzing lotion for dark skin – and take a picture of yourself with the flash on to make sure the colour is just right," says James Read, celebrity spray-tanner to Lady Gaga and Rosie Huntington-Whiteley, among others.
How it works
Physical sunscreens reflect the sunlight before it reaches your skin. The more popular chemical filters neutralise the impact of the sun's rays once they have penetrated the skin – and take up to 30 minutes to take effect.
Gwyneth Paltrow developed ostopenia (thinning of the bone that can eventually lead to osteoporosis) because of low vitamin D levels – and was put on prescription-strength levels of vitamin D and told to spend more time in the sun. In an entry in her online newsletter Goop in July 2010,she said: "I was curious if spending more time in the sun was safe, having been told for years to stay away from its dangerous rays."
There is now evidence that using sunscreen too regularly causes vitamin D deficiency. "Young girls have developed rickets because their well-meaning parents slathered them in sunscreen from birth," says Professor Angus Dalgleish, a cancer specialist a St George's Hospital NHS Trust, London.
Michael Holick, professor of medicine, physiology and biophysics at Boston University, says he is increasingly seeing "sun-phobes who always wear sunscreen" suffering from bone pain and muscle weakness because of vitamin D deficiency.
There is a growing view that sunscreen should be used in moderation. "You don't want to burn. But it doesn't mean you shouldn't have some sun exposure," says Professor Holick.
Oliver Gillie says sunscreen is most valuable for playing sport, when prolonged exposure cannot be avoided. Professor Dalgleish's advice? "Going slightly pink is OK. But put on block at the first tingling sign that you've been over-exposed. But my message is: don't be afraid of the sun."