OK, so technically you may be losing an hour of sleep, but when the clocks go forward by one hour tomorrow you will be gaining so much more in terms of health. And it will require little or no effort on your part.

The extra daylight we all start to enjoy at this time of year has an extraordinary effect on our physical and mental health. There is growing evidence to suggest that we are all chronically deprived of vitamin D - the “sunshine vitamin”, which is absorbed through the skin from the sun's rays - because we don't get enough exposure to the sun.

The ultraviolet rays aren't strong enough to be of benefit during winter, and since we can store vitamin D in our bodies for only about two months, by this time of year we're running on empty.

So by topping up our levels now, with a daily exposure of arms and face for 20 minutes between April and October, we could be preventing serious health problems.

Sunshine vitamin

Research from Bristol University last month suggested that pregnant women who had higher levels of vitamin D produced taller children with stronger bones. Researchers have also linked insufficient vitamin D to heart disease, stroke and high blood pressure, various forms of cancer, multiple sclerosis, diabetes, arthritis and infertility.

Heather Caswell, of the British Nutrition Foundation, in Central London, agrees that you can find vitamin D in food, but says that dietary sources aren't adequate. “Sunlight is the best source,” she says.

Oliver Gillie, of the Health Research Forum, North London, in his recent report “Sunlight robbery”, calls vitamin D “a magic bullet” and suggests a rethink of sun-safety policy, with “regular sunbathing in strong sunlight whenever possible, while taking care not to burn.” (This hasn't gone down too well with many skin cancer charities, which still urge caution: staying in the shade between 11am and 3pm; wearing a hat, sunglasses and using at least factor 15 sunscreen protection.)

Lighter and brighter

Sunlight also helps to regulate many of our body processes, which means that at this time of year we are going to start feeling livelier and more alert. Celia Richardson, of the Mental Health Foundation, says: “Research shows that sunlight has an important role in regulating our bodies' circadian rhythms, the internal clock that affects alertness, cognitive function, sleep patterms; the things that determine our behaviour. We need sunshine in the mornings to reset our body clocks and rev us up for the day.”

Sleep easy

Waking up to the sun and getting early-morning exposure to its light not only affects our behaviour but also can help those suffering from insomnia. According to sleep experts, an hour of sunlight between 7am and 9am each morning is most effective at helping those who have problems getting to sleep at night.

Increased daylight hours may also tempt you to start doing more exercise. Encouragingly, if you are unaccustomed to physical exertion, warm weather reduces your risk of deep-vein thrombosis by helping blood vessels to enlarge, allowing blood to circulate better.

Healthier diet

It's also good news for healthier diets. We are more likely to eat better, with a lower calorie intake, because our increased body temperature makes us less likely to reach for the comfort food that helps to stave off the cold in winter.

Banish the blues

We all feel our mood lift in this weather, too, including those who suffer from seasonal affective disorder (SAD), a depressive condition thought to be caused by the lack of sunshine in winter. “There's a sub-syndromal set of people who have the classical features of SAD - lethargy, tiredness, a compulsion to overeat - but who don't have the more severe symptoms such as depression and anxiety,” says Dr Tish Laing-Morton, the clinical director at the Met Office.

Sound familiar? Don't worry. Levels of the mood-enhancing hormone serotonin, which fall in winter, rise with exposure to sunlight, so hopefully you will be feeling happier soon. “There are lots of things at this time of year that are good for your mental health,” Richardson says. “People are more likely to exercise when the days are longer, and if they have been feeling isolated they go out more, even if it's just into the garden; they socialise more, they take a holiday.”

Get out more

However, don't think that these health benefits will be yours if you just admire the spring view from your office window. “We still may not be getting a sufficient daily dose of sunlight even in summer because the levels are too low in our offices or classrooms,” Richardson says.

“If your room or office has to be lit by artificial light, getting outside in daylight is really important, particularly during the times of day when the sunlight is quite intense. It might even be worth rising with the sun and getting as much of it as you can.”

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