Our obsession with sun avoidance may cause more problems than it prevents, writes Lorna Siggins.
Time was when a "fake bake" wasn't something one admitted to, let alone discussed in detail with friends and colleagues.
Such is the awareness now about the risks attached to prolonged exposure to sun that society tends to be more disapproving of those who have forgotten to lash on the factor 15.
However, British medical journalist Oliver Gillie believes that an obsession with sun protection is seriously flawed, and that some cancer charities are "causing more problems than they are meant to be preventing".
The main "problem" is potential deficiency of vitamin D, which is essential for proper absorption of the bone-building calcium, and can counteract the effects of osteoporosis or thinning of the bones.
The former London Independent medical editor has drawn on a number of studies to prove his thesis that insufficient vitamin D can increase the risk of developing several types of cancer, diabetes, high blood pressure, multiple sclerosis, osteoporosis and can also contribute to depression.
"Most scientific experts tend to take a very narrow view, whereas informed journalists can take a more holistic approach," says Gillie.
"In Ireland and Britain, we get so little sunshine that we developed pale skins to survive. When the first cities developed in the 17th century, problems associated with lack of sufficient sunshine began to emerge - such as rickets in children.
"Now we have televisions, computers, central heating, cars - even air-conditioned tractor cabs for farmers - keeping us out of the light."
There are two types of vitamin D, explains Dr Barbara O'Beirne, director of the Irish Osteoporosis Society. Vitamin D2 can be obtained through diet, such as eating fatty fish, while sunlight is the principal source of vitamin D3.
"As people get older their skin doesn't synthesise sun so well - and they tend to stay in more anyway. An older person with a poor diet who is also out of doors less is at a high risk of vitamin D deficiency and thereby osteoporosis," she says.
One in three women and one in five men can develop the condition as they get older, but it has also been diagnosed in younger people - and was, O'Beirne says, a "hidden disease" for a long time when the focus was on childhood rickets and osteomalacia or bone softening in older people.
She cites a recent study which showed that some 50 per cent of post-menopausal women with osteoporosis in the US were vitamin D-deficient, even in more well-off areas where diet would be regarded as good.
"This may be due to sun avoidance," says O'Beirne. Muslim women who are covered up outside for cultural reasons can also develop serious health problems relating to lack of vitamin D, she points out.
"People don't realise that 10-15 minutes in the sun every day is enough to absorb vitamin D, obtain calcium and still avoid sunburn. Colour from the sun isn't the damaging factor, but burn is. The problem is that people don't know how much sunscreen to use."
Oliver Gillie believes the Irish and British governments should take a lead from Australia, which has revised its policy in relation to sun exposure.
The Irish Cancer Society says that sun-protective measures to reduce skin cancer incidence must "continue as a high priority", but also says that exposure to small amounts of the UVB radiation in sunlight is "essential".
This can be achieved by being outdoors, but fully clothed, for 15 minutes of the day outside of peak UV hours (11am to 3pm).
Vitamin D is not the only factor in osteoporosis prevention, O'Beirne says. "A healthy diet should include three-five units of calcium a day, depending on age, and one should be of normal weight and take regular moderate exercise. One should also avoid smoking, excess caffeine, carbonated drinks and fad diets."
There is also a significant neuromuscular function to the vitamin which helps to prevent falling in older people. Supplements are often prescribed, and the British Medical Association estimates that a daily dose of one gram of calcium and 400-800 individual units of vitamin D is adequate.
Dr Mairead Kiely at University College Cork's department of food and nutritional sciences has undertaken considerable research on the dietary aspects of vitamin D, and is currently engaged with Dr Kevin Cashman and a UCC vitamin D team in a project funded by the British Food Standards Agency on the relative contribution of sunlight and diet.
Some 120 adults in Cork and Coleraine have recently been recruited to monitor their sunlight intake, and the aim is to formulate adequate dietary requirements for vitamin D.
"In Ireland, where we now have everything from pale to dark skin in our population, it is very difficult to come out with an accurate health recommendation on sun exposure, so we believe diet may be the way to source sufficient vitamin D," she explains. "We need to find creative ways to get vitamin D into our foods."
[ www.healthresearchforum.org.ukOpens in new window ]
Understanding Osteoporosis by Prof Juliet Compston, British Medical Association's Family Doctor series.