Sunny D

It's the great cancer cover-up. Panicked into avoiding sunlight by health experts, we are now dying in our thousands from diseases linked to deficiencies of vitamin D. But still the exaggerated warnings come. Oliver Gillie reveals how sunbathing can save your life

How many times have you heard it: "There's no such thing as a healthy tan." Second only to "smoking kills", avoiding the sun is the health warning that has most permeated our consciousness. Young and old, rich and poor, everyone knows that exposure to the sun puts us at risk of skin cancer. But what if the advice we've been given is wrong? What if hiding your skin from the sun is putting your health in danger?

How many times have you heard it: "There's no such thing as a healthy tan." Second only to "smoking kills", avoiding the sun is the health advice that has most permeated our conciousness. Young and old, rich and poor, everyone knows that exposure to the sun puts us at risk of skin cancer. But does it? What if the advice we've been given to avoid the sun is wrong? What if hiding your skin from those seductive rays is putting your health in danger?

While every summer cancer charities and skin experts launch their annual campaign to persuade people, against their natural inclination, to cover up and stay out of the sun, there is growing evidence that lack of exposure to sunlight is responsible for a multitude of disease from multiple sclerosis and diabetes to several types of cancer and schizophrenia. And it's all down to a deficiency of vitamin D - some 90 per cent of which we get from sunlight.

Most medical researchers have been slow in recognising the potentially lethal consequences of vitamin D deficiency. In part this is because vitamin D is not the only trigger for these diseases. However in the British Isles with our long winters and cloudy summers, it seems that insufficient exposure to the sun can make the difference between illness and health, between life and death.

Dr Peter Selby, lecturer in medicine at Manchester Royal Infirmary, says: "Reducing exposure to solar radiation, far from preventing cancer, may have the opposite effect." He points out that a 10 per cent decrease in exposure to sunlight would not greatly reduce skin cancer but could lead to a 6 per cent increase in certain other cancers. And these extra cancer deaths, he points out, would exceed all the deaths from skin cancer put together.

In the UK about 14,000 women a year die of breast cancer - some 40 per cent of these may be caused by deficiency of vitamin D, estimates William Grant, a NASA scientist who has become an expert in vitamin D epidemiology. He calculates that 12-15% of all cancers in the UK, apart from lung cancer, are linked to vitamin D deficiency. That adds up to some 20,000 cancer deaths a year in the UK resulting from too little exposure to the sun, compared with only 2,000 deaths per year from skin cancer of all kinds - not all of which are caused by too much sun. Melanoma, the commonest skin cancer (1,600 deaths per year) may also be caused by diet, overweight and lack of exercise.

Multiple sclerosis is almost unknown in Europeans who are born in South Africa and so in the old days, when doctors worried about the rigours of weather, people with MS were often advised to move to a sunnier climate. Many studies have since shown that MS is more common in cold northern latitudes than it is in sunnier places. In a pioneering study in the 1960s, Professor Sir Donald Acheson, now Dean of Southampton Medical School, found that MS in US war veterans was most closely related to the amount of December sunlight in their place of birth. Winter sunshine, which we now know can make a crucial difference to vitamin D stores, was implicated.

But Acheson's ideas fell on stoney ground. "Sunshine? More like moonshine, what absolute poppycock," one senior colleague remarked in a public put down. It was an idea before its time and the work remained a curiosity, largely forgotten until now.

Over the next 40 years several quite different diseases were found to be linked geographically with MS. Deaths from cancer of the colon and cancer of the prostate were found to be most frequent in the same countries where deaths from MS are most often seen. These were the least sunny northern countries of Europe and the least sunny northern states of the US. Dental decay and rickets were also found to be most common in these areas. And strangest of all, schizophrenia, an extremely disabling mental illness, was found to be more common in the colder northern states of America and in colder northern districts of Italy. While Parkinson's disease, another nervous disorder (causing primarily tremor and stiffness), had a similar geographical distribution.

Theories abounded. Sunlight was too obvious an answer for many researchers. Nor did anyone dare suggest that such different nervous diseases as schizophrenia, Parkinson's disease and MS might all have the same ultimate cause. Perhaps, they proposed, the diseases were caused by viruses? People in the north eat more fat, perhaps that was causing these diseases? Maybe it was all a matter of heredity. The research was like a giant jigsaw puzzle with thousands of pieces. But many important pieces were missing, and thousands of pieces from other jigsaws were muddled up in the same box. Nevertheless, piece by piece connections were made and the jigsaw began to fit together.

According to one school of thought, MS is a hereditary disease of northerners, possibly borne round the world by Vikings. Researchers rushed to find the MS gene. But now Australians, who over the years have received the most dire warnings to keep out of the sun, have found that MS is six times less common in tropical Queensland than it is in Tasmania which has much less sun, particularly in winter. Genetics could not explain the difference: the people of Tasmania and Queensland have the same Anglo-Irish and European ancestors. Children in Tasmania who did not develop MS were more likely to have spent two to three hours a day playing outdoors in summer during weekends and holidays. Maybe these diseases can be prevented by playing in the sun. Fun in the sun, could the answer be so simple?

Then came a breakthrough. MS is caused by patches of damage in parts of the brain and spinal cord leading to severe disability and eventually paralysis. The symptoms come and go. People with MS may improve for a while and then relapse for no apparent reason, until now. Brain scans of people with MS investigated by a team of scientists in Germany have shown that the number of MS lesions increase during winter when the amount of vitamin D in the body declines.

And other pieces of the jigsaw were falling into place. In 1992 Gary Schwartz, a researcher at the University of Pittsburg, suggested that the common factor linking MS and prostate cancer could be vitamin D. Schwartz showed that consumption of cod liver oil (a good source of vitamin D) in youth reduces the risk of prostate cancer in old age. Finally evidence linking prostate cancer directly with sunlight came two years ago from Professor Richard Strange and colleagues at Keele University. They found that men in North Staffordshire with prostate cancer had had substantially less exposure to the sun than men who did not have prostate cancer. On average, men who had least exposure to the sun developed prostate cancer four years earlier than men who had more exposure. Regular foreign holidays and sunbathing were found to protect against the disease.

Northern Europe is not man's natural environment. Recent studies of human DNA tell us that man evolved in Africa. Small bands of people left the African continent some 80,000 years ago following the southern coast of Asia, and eventually colonising what is now Iraq and Iran. These people, who were almost certainly dark skinned, moved into Europe via Turkey, the Black Sea and the Mediterranean as the northern ice cap retreated some 50,000 years ago. The story of this epic human journey has been reconstructed from modern DNA studies and is told by Oxford professor Stephen Oppenheimer in his authoritative book "Out of Eden".

The virgin territory of Europe must have supplied plentiful food in summer but in winter not only was food in short supply, low levels of vitamin D must have increased the susceptibility of these pioneering bands of people to disease and reduced their fertility. Dark skin takes six to 10 times as long as white skin to make a given quantity of vitamin D and so those with lighter skins would have had an advantage as the pioneers moved north.

The importance of skin colour for human survival outside the Tropics has been shown by Dr Nina Jablonski of the California Academy of Sciences in San Fransisco and George Chaplin of Manchester Metropolitan University. They found that skin colour of 180 different indigenous peoples is linked closely to the amount of autumn and winter sunlight where they live. Not only do native peoples everywhere have paler skins the further they live from the equator, but women and children in the human groups studied by Dr Jablonski always had paler skins than men, a neat adaptation to provide the maximum vitamin D that is needed for fertility in women and growth in children.

Northern Europe was the end of the line for the successive waves of people travelling through Turkey and the Balkans after the ice age. It was further north than man had ever lived before and the cloudy maritime climate of the British Isles and other countries bordering the North Sea have reduced sunlight even in summer. And so Europeans evolved a pale skin that enables the first weak rays of spring sun to be used to make vitamin D. This enables body stores of the vitamin depleted during winter to be replaced at the earliest opportunity, while tanning provides some protection as sunlight becomes stronger over the summer. For thousands of years into historic times, Europeans living an outdoor life in the countryside do not seem to have suffered from obvious vitamin D deficiency.

But in the past 400 years, when large numbers of people began to congregate in towns and cities a severe problem of vitamin D deficiency developed. In 1650, treatises were written on rickets, the bone deforming disease of children that became known as the English disease. The disease was most common in cities, where narrow streets and air pollution prevented the penetration of the sun. Children developed deformities of the legs which made it difficult for them to walk and women suffering from the disease had flat deformed pelvises which caused difficulty in childbirth.

The link between rickets and lack of sunlight was not made until 1822 when a Polish doctor noted that children living in Warsaw frequently suffered from the disease while children living in the surrounding countryside did not. He recommended fresh air and sunlight. In 1889 the British Medical Association reported that rickets, common in cities, was unknown in rural areas. A year later another British doctor reported in the Practitioner that rickets did not occur among the poor living in the city slums of China and India and concluded that exposure to sunlight would prevent the disease. It would be another 30 years before these ideas began to be accepted.

The demonstration in 1919 that ultra-violet light from a mercury arc lamp could cure rickets in children provided dramatic scientific "proof" that rickets was caused by lack of sunlight. At about the same time it was shown that cod liver oil (which is now known to be rich in vitamin D) could cure rickets in dogs raised exclusively indoors. It took a few more years for scientists to chemically identify vitamin D and show that it was responsible for the ability of cod liver oil to cure rickets. By the 1930s vitamin D was being added to foods such as margarine and rickets became relatively rare.

The discovery of vitamin D was an early triumph of modern science which caught the public imagination and fed the craze for city people to seek health in the open air. Cycling, rambling and youth hostelling all became immensely popular between the two world wars - a movement which reached a summit of sorts with the invention of the bikini by a French engineer in 1946. The full delight of sun on naked skin was re-discovered and forty years of carefree sunbathing followed before the spectre of skin cancer cast its pall over summer fun.

Nicolai Gogol's short story Dairy of a Madman (1834) is one of the earliest and most complete descriptions of schizophrenia. Brief accounts of the disease had appeared in Paris and London in 1809 but, with the possible exception of the character Poor Tom in Shakespeare's King Lear, earlier descriptions of schizophrenia do not seem to exist. Schizophrenia appears to have been virtually unknown before 1800 while most other psychiatric and nervous diseases such as epilepsy are described in the Old Testament or other early historical works.

These literary observations made by Dr Eric Altschuler of the Brain and Perception Laboratory at the University of California provide historical support for a theory that schizophrenia may be caused by a deficiency of vitamin D during pregnancy. Schizophrenia, it seems, emerged as a new disease with the great expansion of modern European cities, at much the same time as rickets began its most devastating phase.

For many years geneticists claimed that schizophrenia was an inherited disease and poured scorn on other ideas. But they were at a loss to explain why people with schizophrenia had winter birthdays more often than would be expected. Extra vitamin D is required in the last three months of pregnancy to support the rapid growth of the baby. When the level of the vitamin is low, as occurs most frequently in winter, there may not be enough to provide for normal development of the brain or other organs causing more winter births of people with schizophrenia.

The nervous system of the developing baby may be damaged in other ways by vitamin D deficiency. Other diseases which occur more frequently than would be expected in babies born in winter or early spring are autism, Alzheimer's disease, Parkinson's disease, and MS. The cause of these diseases is still being hotly debated by experts but vitamin D deficiency is one theory that is gaining increasing support. Like schizophrenia, these diseases may appear to be more strongly inherited than they really are because family members influence each other in the way they seek or avoid the sun.

Schizophrenia is one of several diseases that has been found to be more common among dark-skinned people than among whites in Britain. Diabetes, multiple sclerosis, autism and rickets have also been reported to be more frequent among immigrant families who came to Britain from Tropical countries. First generation immigrants born in the Tropics are no more vulnerable to schizophrenia than native British whites, but the disease is more frequent among their children than among white British people, according to several research studies led by Professor Glynn Harrison at the University of Nottingham, Dr Dinesh Bhugra at the Institute of Psychiatry, London, and others.

Many explanations, including prejudice, psycho-social stress and inheritance have been considered, but they do not explain the facts. Investigators have repeatedly pointed to the consistency of their findings and concluded that an environmental factor must be responsible. Now in the light of other research it seems obvious that deficiency of vitamin D, caused by the slow absorption of ultra-violet light by black skin and low levels of sunlight in northern climates, is the most likely explanation for the increased incidence of these diseases in immigrant families.

Not only are more people with schizophrenia born in winter, the number of people born each year who later develop the disease varies from year to year in a way that cannot be explained by chance. Investigations by Dr John McGrath and others at the University of Queensland have linked this variation in births of schizophrenic people with the amount of sunlight around the time of their birth. The observations fit in neatly with new findings that show the importance of vitamin D for growth of cells and for the development of the brain.

Dr McGrath, an Australian who is currently working at Harvard University, says: "Queensland, where I live, is in the Tropics so we get strong sun all the year round. I try to sit out in the sun every day and when I go to the beach with the children we have a half hour of exposure to the sun before we put on any suncream. Sunlight is specially important for pregnant and nursing mothers."

Babies in Finland often used to be given very large doses of vitamin D in the first year of life and now Dr McGrath, working with Finnish doctors, has shown that men who were given these large supplements as babies are less likely to develop schizophrenia than men who were not given the supplement. This same group of men given vitamin D as babies have been found to be less likely to develop diabetes before the age of 30. And in the UK people with this type of juvenile diabetes (known as diabetes type 1) are more likely to be born in the winter or early spring months when vitamin D is in short supply.

In juvenile diabetes the beta cells in the pancreas that normally produce insulin do not develop properly and are attacked by the body's own immune system. Deficiency of vitamin D is probably what causes these cells to develop abnormally, triggering the assault. Now a dramatic demonstration that vitamin D can rescue beta cells that are being attacked in this way is likely to sway scientific sceptics. Two independent trials conducted in Rome and Munich have shown that giving vitamin D to children when diabetes is first diagnosed can save the beta cells, at least temporarily, and delay development of the disease.

But these trials of the health benefits of vitamin D supplements are exceptional. Few trials have been made of vitamin D for treatment of diseases other than bone disease because the vitamin cannot be patented and drug companies cannot justify expensive trials which will not lead to profits. However trials of several compounds similar to vitamin D have begun recently for treatment of cancer because these compounds can be patented.

Crucial pieces of the jigsaw puzzle now seem to be in place and a consistent picture has emerged although many researchers remain sceptical, especially those who have spent most of their lives committed to other theories. The sceptics point to technical difficulties in the scientific evidence and the lack of final proof that vitamin D is the cause of most of these diseases. But the weight of so many different studies demonstrating or suggesting the health benefits of sunbathing and vitamin D supplements can no longer be overlooked.

Yet every year doctors repeat the mantra: "There is no such thing as a healthy tan," words which are enshrined in a Consensus Statement of the UK Skin Cancer Prevention Working Party and endorsed by more than a dozen health charities as well as by UK government health departments. And every year doctors complain about the large number of people who ignore their advice by sunbathing and tanning.

The advice of the Skin Cancer Working Party has of course been given in good faith with the very best of intentions but it is based on a mistaken Consensus. It can no longer be defended. The stark truth is that advice to avoid the sun has put more lives at risk than it can possibly have saved and, it must be faced, is responsible for many thousands of deaths.

Dr Neil Walker, chairman of the UK Skin Cancer Prevention Working Party, says: "The phrase 'no such thing as a safe tan' is one way of getting the message across that sun damage can lead to the development of potentially fatal skin cancers. I think we need to look at this again. Personally I advise my patients not to bake and not to burn. I think telling people to avoid the sun entirely is draconian and unnecessary."

In fact, there is much scientific evidence showing that regular exposure to the sun does not necessarily carry any increased risk of skin cancer. Heavy occupational exposure to the sun such as is seen in farmers and construction workers is associated with a reduced risk of melanoma, the worst type of skin cancer. When care is taken not to burn, intermittent exposure to the sun probably carries relatively little risk of skin cancer, and provides a very great benefit from the vitamin D it gives.

This much has been clear since at least 1997 when Mark Elwood, a distinguished scientist at the University of Otago, New Zealand, published a review of 50 studies of melanoma and sun exposure in the International Journal of Cancer. The Consensus should have been redrafted then, but its momentum, financed by government and World Health Organisation funds, has proved to be unstoppable. Until recently, few skin cancer experts were prepared to recognise the probable role of vitamin D in preventing other cancers, there was little understanding of how important vitamin D is for prevention of other diseases, nor were skin experts prepared to concede that regular sunbathing or use of supplements is needed to provide adequate levels of vitamin D in our climate.

"It is safe to say that the cost of vitamin D deficiency is billions of dollars. How many billions is the issue," says Professor Robert Heaney of Creighton University, Omaha, Nebraska, who has made many studies of vitamin D and disease.

The cost of disease believed to be caused or exacerbated by vitamin D deficiency has been estimated by Wiliam Grant to be some 50 billions of dollars in the United States. The cost to the UK National Health Service of just one disease, diabetes type 1, which can probably be prevented by vitamin D supplements, runs to £500m a year or about 1 per cent of the NHS budget. The total cost of D deficiency disease to the UK must certainly be calculated in billions of pounds.

"This is money that really could be saved if people generally took supplements of vitamin D or sunbathed regularly," says Professor Heaney.

Part two