For years, the sun has been public enemy No1, causing skin damage, premature ageing, skin pigmentations and increasing our risk of skin cancer.
But before you head for the shade, consider this: those nasty rays are needed in the production of a crucial hormone, vitamin D, and by completely blocking out the sun you are risking a deficiency that could leave you open to all sorts of ailments.
An increasing number of scientific studies are now pointing to vitamin-D deficiency as being a factor in a catalogue of illnesses including colds and flu, heart disease, strokes, diabetes, autoimmune disorders, depression, osteoporosis and many cancers. It has even been suggested as a possible cause of autism.
At the root of the rate of deficiency is the habit of shunning the sun and using sun block, says the vitamin-D pro-camp. Add to that lifestyle factors that mean we live a much more indoor existence than our ancestors did and you have a population that is not getting enough sunlight to produce the vitamin D their body needs.
About half of Americans are believed to have insufficient levels of vitamin D, while a recent study by the Li Ka Shing Faculty of Medicine at the University of Hong Kong revealed that more than 60 per cent of Hong Kong people were deficient.
Professor Annie Kung Wai-chee, who led the study, says men fared the worst, possibly because they are likelier to be working long hours indoors.