Here comes summer, just about, and despite years of vigorous health campaigns many of us will still be surrendering our milky-white bodies to the mercy of the sun. We find it hard to give up burning our flesh, even though it is now as much maligned as smoking or stuffing down cream cakes. One 1997 survey showed that despite high levels of awareness about the dangers, more than a third of men and around half of women who did not have a naturally black or brown skin had tried to get a tan the previous year.

Ironically, people say that a good roasting improves their sense of wellbeing, and that a tan makes them feel healthy, sexy even. Are they right? Could sunbathing be good for us? If this article were being written in the early 1900s the health-giving aspects of the sun would be exalted.

It was found during the first world war that wounds healed quicker if left exposed to the sun, and patients with tuberculosis were healed in clinics where they were wheeled out onto balconies or into solariums. In the 1930s, sunbathing was encouraged as a public health measure. Heliotherapy (sun therapy) was also used to treat rickets, burns, varicose ulcers, osteomyelitis (an infection of bone), septic abscesses, anaemia and fractures.

Archive photographs of sunbathing hospital patients now look bizarre in an era when we are told that there is no such thing as a healthy tan and that we should cake ourselves in SFP 15 sunscreen and avoid exposure between 11am and 3pm. Those, however, were the days before antibiotics, when anything that apparently boosted the immune system had to be taken very seriously.

Sunlight has the ability to kill bacteria, even when it passes through glass, and it has been found that patients recover faster in sunny hospital wards. "In the right hands, sunlight is a medicine," claims Richard Hobday, author of The Healing Sun (Findhorn Press £9.95), a new book which explores the beneficial effect of sun on our health, and hopes to redress what the author sees as our current bias against sunlight. "Each year lack of sunlight probably kills many thousands more people in this country and others at similar latitudes than skin cancer," he says.

The sun is certainly a natural healer, so it's not surprising that this call for its reinstatement comes from those whose sympathies are based in complementary therapy: Hobday is trained in traditional Chinese medicine, and the book is published by Findhorn, the New Age community in Scotland.

However, his dramatic assertions are also echoed by four epidemiologists from the department of social medicine at Bristol University. Their article "Are we really dying for a tan?", published in the British Medical Journal last summer, controversially claimed that "the exact nature of the association between malignant melanoma and exposure to sunlight has to be determined", and that "there is evidence that the potential benefits of exposure to sunlight may outweigh the widely publicised adverse effects on the incidence of skin cancer".

Hobday, who is a doctor of engineering, became interested in sunlight as medicine when investigating solar energy technologies, and learnt of a lost tradition of designing sunlit buildings to prevent disease. "Also I am particularly fond of sunbathing and only feel fit and well when I have a tan," he says.

The fact that sunlight enables us to manufacture vitamin D is key to its health giving properties. Vitamin D is essential for the growth and maintenance of teeth and bones and a healthy immune system. In Britain we get only a quarter of it from diet (the main sources are margarines and dairy spreads, fatty fish, breakfast cereal and eggs), and the rest from the sun. The evidence is sketchy, but a vitamin D deficiency may be linked to a long list of ailments, including osteoporosis, heart disease, diabetes, and cancer.

On skin cancer, of which there are now about 40,000 new cases every year in the UK, Hobday points out rather lightly that the non-melanoma variety, which accounts for a vast number of cases, doesn't matter too much because it is treatable. Malignant melanoma, (about 4,000 cases annually) he argues, is most prevalent amongst people who spend long periods indoors and then go for the burn on their two-week holidays, rather than people who work outdoors.

Writing for the British Medical Journal in response to "Are we really dying for a tan?", Professor Hawk, an expert in dermatological photobiology at London's St Thomas's Hospital, argues that the "warmth and light of sunlight are the only rays we need, and ultraviolet radiation exposure is definitely harmful to human skin". He says vitamin D is readily available in the normal diet and "there is therefore no evidence whatsoever that ultraviolet radiation avoidance leads to vitamin D deficiency".

Hobday argues that there are no internationally agreed figures for the amount of vitamin D required to stay healthy. He is dismayed that we have to rely on fortified foods to keep up supplies. "There is a great deal to be said for getting out in the sun for short periods during the spring and summer," he says.

So should we dare to bare? The International Smart Tan Network is an American organisation which promotes moderate suntanning and sunbed use. Joseph Levy, its director argues that "sun abstinence only makes people more likely to sunburn when they do go outdoors", and that the gradual development of a moderate tan is the best and natural way to protect ourselves from the sun.

If we do decide that public health messages have become too cautionary, it would be unwise to strip off with abandon. Professor Anthony Quinn, a dermatologist at the Royal London Hospital, doesn't see how the benefits outweigh the risks. "I don't think we are being cautious enough," he says.

Even Hobday advocates a highly restricted sunbathing routine. For starters, you need to stay cool. According to the heliotherapists of yesteryear, particularly Dr Auguste Rollier, who became known as the "high priest of sunlight therapy", you must sunbathe in cool conditions so that your body is simultaneously trying to generate heat. This is believed to be more therapeutic. Air temperature shouldn't be higher than 18C or 64F, which means that spring, early summer and autumn are the optimum times, and you need to find a sheltered spot if you are to avoid goose bumps.

Early morning sun is the best, and frequent short exposures are better than long periods. Don't wear sun creams, but protect the delicate skin on the face by wearing a hat. If you are very sensitive to the sun you might try the "Rollier method": cover yourself with a white sheet, and on the first day raise it to just above the ankles for five minutes. On subsequent days repeat, progressively unrolling the sheet upwards.

Sunlight in moderation it may be good for...

Brittle bones Sunlight deprivation has been linked to weak bones. Vitamin D deficiency is linked with increased risk of hip fracture. Bone density is at its lowest in the winter.

Rickets Very rare today, but develops when people are deprived of sunlight.

Tuberculosis Sunlight can help prevent it developing in susceptible individuals by keeping up their vitamin D levels. It can also prevent spread of the disease by killing bacteria in the home.

Cancer Vitamin D is involved in the growth and maturation of cells. In laboratory experiments the biologically active form of vitamin D has been shown to inhibit the growth of cancer cells. Although sunlight can cause skin cancers, studies have shown that the nearer you live to the equator the less chance you have of developing an internal cancer.

Heart disease Sunlight is effective in lowering blood pressure and cholesterol levels.

Diabetes Vitamin D has been shown to have a protective effect against childhood diabetes.

Psoriasis Heliotherapy can help clear up this skin condition.

Mental health People enjoy sitting in the sun. Seasonal variations in sunlight may underlie a proportion of episodes of depression. Suicide rates rise in winter.