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The benefits of sun exposure in reducing blood pressure may outweigh the risks of developing skin cancer, scientific research has found.
Nitric oxide, a pressure-reducing compound, is released in the blood by ultraviolet (UV) rays produced by the sun and artificial sun lamps, and can cut the risk of heart attacks and stroke, the new study claims.
It was conducted by University of Edinburgh scientists who measured the blood pressure of 24 volunteers sitting beneath UV lamps for two 20-minute sessions.
They now say that guidelines on safe levels of exposure to the sun may need to be reconsidered.
In the first session the volunteers were exposed to the lamps' UV rays and heat, while in the second session the UV rays were blocked so that only the heat of the lamps affected the skin.
Blood pressure dropped significantly for one hour following exposure to UV rays but no change was recorded after the heat-only sessions, the results show.
Vitamin D had previously been thought of as the only health benefit from UV rays but the scientists say their experiments show additional positive effects.
Dr Richard Weller, senior lecturer in dermatology at the university, said: ``We suspect that the benefits to heart health of sunlight will outweigh the risk of skin cancer. The work we have done provides a mechanism that might account for this and also explains why dietary vitamin D supplements alone will not be able to compensate for lack of sunlight.
``We now plan to look at the relative risks of heart disease and skin cancer in people who have received different amounts of sun exposure. If this confirms that sunlight reduces the death rate from all causes, we will need to reconsider our advice on sun exposure.''
Heart disease and stroke linked to high blood pressure causes around 80 times more deaths than those from skin cancer, the researchers said.
The British Association of Dermatologists said the results of the study should be treated with caution. Director Nina Goad said: ``While this is interesting, these preliminary data on just 24 healthy volunteers with one hour's observation could be explained by many factors and variables not related to the sun.
``The findings do not confirm sustained blood pressure reduction in the general population. Research in this area is still very much in its infancy. Emerging evidence about possible health benefits of sunlight do not invalidate the indisputable weight of evidence showing the link between excess UV exposure and skin cancer, which is the UK's most common form of cancer.
``It's also worth noting that there are many other ways of achieving sustained reductions in blood pressure with evidence-based interventions that do not involve the risks associated with getting too much sun.''
The proof-of-principle study will be presented at the International Investigative Dermatology conference in Edinburgh on Friday.