SITTING in the sun has long been seen as a health risk, but new research by Scots scientists has found the benefits of catching a few rays outweigh the negatives.

Researchers at Edinburgh University found exposing skin to sunlight may help to reduce blood pressure and the risk of stroke and heart disease.

The findings fly in the face of recent medical advice to people to cut down the amount of time they spend in the sun amid warnings it could lead to a higher risk of contracting skin cancer.

The Edinburgh team found getting a little sun helps produce a chemical compound in the body linked to good health.

Scots are said to get 400 fewer hours of sunshine a year than the south coast of England, where health records are better.

Exposure to sunlight is known to produce vitamin D, which has long been recognised as reducing the chances of contracting certain types of disease including allergies, childhood rickets, osteoporosis, and rheumatoid arthritis.

Last year, Sir Harry Burns, Scotland's Chief Medical Officer, advised doctors to be aware of the dangers of vitamin D deficiency.

Those at risk include pregnant and breastfeeding women – especially teenagers and young women – children aged under five, older people aged 65 and over, and those with low or no exposure to the sun. All were advised to take a vitamin supplement.

However, the Edinburgh group found sunlight is also instrumental in producing the pressure-reducing compound nitric oxide, separately from vitamin D.

The findings were reported in a landmark proof-of-principle study which tested the blood pressure of 24 volunteers. Each was exposed to a tanning lamp for two sessions of 20 minutes. In one session, the volunteers received both ultra-violet rays (UV) and the heat of the lamps, while in the other the UV rays were blocked so only the heat of the lamps affected the skin.

Blood pressure dropped significantly for one hour after exposure to UV rays, but not after the heat-only sessions. Scientists say this shows it is the sun's UV rays that lead to health benefits. The volunteers' vitamin D levels remained unaffected in both sessions.

Dr Richard Weller, senior lecturer in dermatology at Edinburgh University, said: "We suspect 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 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 sunlight reduces the death rate from all causes, we will need to reconsider our advice on sun exposure."

Figures released last month showed that two out of every five people will have some form of cancer in their lifetime. The number of people with skin cancer has increased by more than 50% in the last decade.

The new research will be presented at the International Investigative Dermatology conference, which starts in Edinburgh today and runs until Saturday.

Yinka Ebo, senior health information officer at Cancer Research UK, said: "This is interesting research but it's yet to be published in a peer-reviewed scientific journal. Overexposure to UV radiation from the sun is a main cause of skin cancer. We all need some sunshine to make vitamin D to keep us healthy, but most people can get a good balance by enjoying the sun safely and taking care not to burn.

"Sunburn is a clear sign that your DNA has been damaged, and over time this damage can build up and lead to skin cancer.

"The best way to protect your skin from sunburn when you're out in strong sun is to spend time in the shade, pop on a t-shirt and use at least factor 15 sunscreen, applied generously and regularly."