Helen McArdle reports on medical evidence linking the dourness of the Scots to the dullness of our weather

WHILE fears over skin cancer have led many to believe they should avoid exposure to ultra-violet rays as much as possible, evidence is now emerging that a lack of sunlight could be linked to illnesses such as depression, cancer and multiple sclerosis.

On Monday, London-based researcher Dr Oliver Gillie linked Scotland's poor health record to a widespread vitamin D deficiency, caused by the country's extremely low levels of sunlight.

In his study, Scotland's Health Deficit: An Explanation And A Plan, Gillie urged the Scottish government to take action by encouraging people to take supplements, adding that doctors could prescribe "megadoses" of up to 50 times the current average daily intake of vitamins to combat major deficiencies.

According to data compiled by the Met Office, the below-average levels of sunshine this year conform to a decade-long trend. "The noughties in Scotland have fared particularly poorly with regard to sunshine," said spokesman Barry Gromett. "Four out of the past nine summers have been in the bottom 20."

Scotland has enjoyed just 385.8 hours of sunshine during June, July and August, compared with an average of 435.7 since records began in 1929. The figures are a far cry from 1995's peak, when Scots basked in 634 hours of golden rays. However, the gloomiest is still 1980, with just 329.2 hours.

The Met Office also divides its Scottish statistics into three regions - northern, eastern and western. Perhaps surprisingly, the north, which covers the Highlands and Grampian, actually received a comparatively higher share of sunshine than elsewhere in Scotland.

"Northern Scotland got 99% of its expected sunshine, while the western region received 84% of its average this year and eastern Scotland 82%", says Gromett. "So, while the total number of hours of sunshine is highest for western Scotland, with 389.8 hours, northern Scotland, having had 387.5 hours, actually fared better in relation to its average."

Sunshine levels are traditionally monitored using a Campbell-Stokes sunshine recorder, a glass ball which focuses the sun's rays onto treated paper, burning a trace in the same way as a magnifying glass would. However, as weather stations modernise these are gradually being replaced by radiometers, which measure amounts of strong radiation in the sunlight.

Many scientists agree that if the trend for gloomy Scottish summers continues, it could pose a serious danger for Scots' health and wellbeing, but not everyone agrees with Gillie's recommendations.

Dr Rafe Bundy, lecturer in nutrition at Glasgow University, says: "The vast majority of vitamin D is generated by the body in reaction to the sun's ultra-violet B rays, but unlike other vitamins there are few foods which can help plug the gap caused by a shortage of sunshine.

"Dietary sources are very few - fatty fish such as mackerel and sardines are really the only strong sources of vitamin D. Our diets are really a very poor source, which is why there is fortification of products such as margarines. To try to eat a diet high in vitamin D is actually quite difficult."

However, he says, substituting sunlight for supplements may not be an effective solution either: "Let's say I'm out in the sunshine for five minutes - that would make enough vitamin D for the day. If I'm out for 20 minutes then, do I overdose? Well actually, the body, being the clever structure it is, will use sunlight to break down any surplus vitamin D produced from prolonged exposure to the sun. In effect, it sets a natural upper limit.

"But of course, with oral supplements, there is a potential risk of taking too much, because they can override the body's metabolism and continue being absorbed even after the optimum level has been reached. So, as a public health message, I think it's dangerous at this stage to say we should all be taking much higher doses."

Given the role that vitamin D plays in regulating and depositing calcium in the body, the side-effects of overdosing can include kidney stones, caused by a build-up of calcium in the soft tissues. On the flipside, a deficiency results in softening of the bones and rickets in children. Asian immigrants to Scotland have been particularly badly affected, because their darker pigmentation acts as a natural barrier against UV rays, meaning they can generate even lower levels of vitamin D than white people.

However, some scientists now fear deficiencies may underpin other serious illnesses. Bundy says: "The general feeling is that low vitamin D might mean conditions like cancer, diabetes and multiple sclerosis are more prevalent. There have been a lot of interesting links made, but most in the scientific community still agree there's not enough data yet to make any categorical recommendations. It's more that there is an apparent association between poor health and low levels of sunshine."

This is not a green light for sunseekers, however. Scientists are still divided on how best to manage the compromise between skin cancer dangers and vitamin D deficiency. The best advice at the moment seems to be moderation at both ends: five minutes of midday sunshine on a hot day would maintain healthy levels of vitamin D, but exceeding 15 minutes could pose a cancer risk.

However, to add to the dilemma, vitamin D may also be linked to the prevention of other cancers. Sara Hiom, Cancer Research's UK director of health information, said: "There is some evidence that vitamin D has a role to play in preventing certain cancers, most notably bowel cancer. But there is still a way to go before we fully understand the link between a person's vitamin D levels and their risk of cancer. We are waiting for the results of an international report on all the evidence linking vitamin D and cancer, due out later this year."

Mental wellbeing has also been associated with sunshine. Professor Patrick O'Donnell, of Glasgow University's psychology department, says: "Vitamin D itself may hormonally enhance mood by encouraging the production of seratonin. There is some evidence that not just seasonal affective disorder (SAD), but other depressions, may be linked to vitamin D deficiency, the main source of which is sunlight's action on the skin. But that's still very suggestive at the moment.

"The other mechanism that seems to be proven is that the change from poor weather to sunshine does produce a short-term effect of enhancing mood, particularly for people in northern climates.

"However, that might not be the direct effect of sunshine so much as its association with doing things you enjoy - getting out more, seeing friends, engaging in sport and leisure pursuits."

Some 7% of Scots will develop full-blown SAD, a form of depression triggered by a lack of sunlight. Although more typical in winter, drab summers can prolong the condition. A spokesperson for Depression Alliance Scotland said: "During particularly overcast Scottish summers, where there is not much sun, those affected by SAD may experience symptoms.

"But depression is usually caused by a mixture of factors. Rainy grey days, such as we have had, make it harder for people to get outdoors and keep active, which can also impact on our mood.

"There are things that people can do to help relieve symptoms: Make the most of dry spells and get outside as often as possible. Taking regular exercise, such as going for walks, has been proven to be helpful, and keeping up social activities can be an important source of support. Some people with SAD find that light boxes provide a helpful boost during darker months, which also helps to reduce symptoms.

"People affected by SAD will experience symptoms similar to general depression. These might include feeling low, irritable and anxious. Withdrawing from social activities, feeling too tired to cope and overeating are other typical symptoms."

A lack of the naturally mood-enhancing effects of sunlight could also be a contributory factor in Scotland's year-round drinking culture, says O'Donnell.

"Research shows that alcohol abuse generally increases the further you are from the equator, so it may be that it's being used as a mood-enhancer. However, the links between alcohol and depression are so complex - socio-economic and cultural factors, such as the position of women, are involved - that it is difficult to assess what role sunshine could play."