"Regular, brief exposure to UVB light not only increases levels of vitamin D, but also reduces blood pressure. To ensure an adequate supply of vitamin D people should expose their hands, arms, and face to sunlight for 5 or 10 minutes a day two or three times a week. This will not significantly increase the risk of skin cancer," said Michael Holick, director of the vitamin D laboratory at the Boston University School of Medicine.
But the American Academy of Dermatology, the Yale School of Dermatology and the Sun Safety Alliance say the claims are scientifically unsound and misleading to the public, comparing the idea of sunning to prevent vitamin D deficiency to the idea of smoking to combat anxiety.
"In my two decades of practice I've never seen vitamin D deficiency caused by lack of sun exposure due to sunscreen use, there is no acceptable dose for carcinogens like UV radiation" says Dr David Leffell of the Yale School of Medicine Department of Dermatology.
Vitamin D is fat-soluble, like vitamins A and E. It has long been recognized as major factor in controlling the balance of calcium in the body. Unlike other vitamins, it is not generally found in food.
Between 90 to 95 percent of all our vitamin D comes from casual, everyday exposure to sunlight. The vitamin is made in the skin by a complex synthesis process that uses the ultraviolet B (UVB) portion of sunlight.
The new report - published in the British medical journal Lancet - compared the levels of vitamin D in people living in north eastern cities - where UV rays do not penetrate in winter months - and people who lived elsewhere and used sun block.
The report found that the same vitamin D deficiencies were apparent in both groups.
The new study comes at a bad time for the suncream industry who is having to re-evaluate the effectiveness of sun protection factors (SPF's) in light of new research.
University of Sydney researchers found that UVA rays - which age the skin but do not burn - can also cause DNA damage. The finding suggests sunscreens must now not only protect against UVB rays but also UVA to protect against cancer.
"The importance of protecting the population not just from UVB but also from UVA irradiation has profound implications on public health worldwide," said australian researcher Gary Halliday.