Vitamin D: The sunshine cure

The voice was calm, despite the devastating news: "I have cancer of the pancreas. Do you know anything about it?"

Yes, I did. It's a killer, not something I wanted to tell a friend on the phone. Most people with pancreas cancer only have months to live after the diagnosis. So I was evasive. The next question showed that my friend Annie already knew her situation was desperate: did I know of any new treatments?

Yes, again. A London teaching hospital was exploring a new photodynamic treatment for pancreas cancer and having some success. I told her about it but she had already been advised that her tumour was unsuitable for the new treatment because it was too close to a large artery. She probably had even less time than I had thought.

But there was another possibility that might provide some hope in an utterly hopeless situation. At the time, I was studying the scientific literature linking chronic disease to insufficient sunlight and vitamin D. I knew that there was data showing a strong link between bowel cancer and lack of sunlight. This had been known for more than 20 years, although few doctors or scientists had shown much interest in it.

I quickly scanned the literature on pancreas cancer and, yes, there was a clue: in 1998, some Japanese scientists had found a correlation between the number of deaths from pancreas cancer and latitude. People living in countries further north, where there is less sun and vitamin D levels are lower, are more at risk of pancreas cancer. It seemed to follow the same pattern as bowel cancer.

If insufficient vitamin D was a cause of pancreas cancer, then perhaps taking vitamin D might do something to stop the cancer, or at least slow it down. It was a leap in the dark but surely worth considering. But how much vitamin D should a person take? I had no idea. I spoke to Annie a few more times on the telephone and helplessly followed her decline which, as expected, occurred rapidly within a few months. Annie was only 57 years old when she died.

Soon afterwards I heard that a family friend, Mary, a lifelong smoker, had cancer of the lung. The cancer had been discovered early in an X-ray taken to find the cause of a long-standing backache. The tumour was removed by surgery and her life appeared to return to normal, although she still suffered from backache.

In the course of my studies of vitamin D, I had learnt a little-known fact: unexplained backache in old people is frequently caused by insufficient vitamin D. I suggested that she take cod-liver oil capsules, a good source of vitamin D as well as providing friendly fish oils. She tried them but didn't like them. I later learnt that they did not contain enough vitamin D to have made much difference.

Mary tried to continue with life as before, but twice she fell while out shopping and, frightened of falling again, she stopped going out except when she was with family and knew she was safe. Muscle weakness, causing falls, is another well-established effect of insufficient vitamin D.

By this time, I had found some higher-strength vitamin D in small, tasteless tablets, thus easy to take, but Mary had no confidence that they would make any difference and didn't take them. I thought they might at least improve her general health and, who knows, they might have helped her body to fight the cancer that gradually began to return. Vitamin D for lung cancer - it seems a forlorn hope. We all know that lung cancer is caused by smoking. But scientific evidence emerging in the last few years has shown that insufficient vitamin D is associated with an increased risk of some 18 or more different cancers. And even lung cancer seems to respond to vitamin D.

A year ago, Wei Zhou, a researcher working with Dr Edward Giovannucci, Professor of Nutrition and Epidemiology at Harvard School of Public Health, reported that vitamin D seems to aid survival of lung cancer patients. Patients with the highest vitamin D intake who had surgery in summer, when their vitamin D levels were highest, were twice as likely to be alive five years later as patients who had the lowest levels of vitamin D and had surgery in winter.

This is just one small study, but similar results have been obtained in Norway and, now, in England, by Professor Henrik Moller, working at the Thames Cancer Registry, of which he is director. Professor Moller found that people with cancer, especially breast and lung cancer, lived longer following their diagnosis if the weather was sunny in the weeks and months preceding the appearance of the disease.

These studies cannot prove cause and effect, but they are part of an emerging pattern of scientific work that suggests that cancers grow most rapidly in people who have insufficient vitamin D. In April this year, Professor Giovannucci and colleagues reported the results of a major study of more than 4,000 cancers occurring in 47,800 men, known as the Health Professionals Follow-Up Study. He found that the men with the highest vitamin D index had a 17 per cent reduction in cancer, compared with the men who had the lowest vitamin D index - and they had an even greater reduction in deaths from cancer (29 per cent), showing that high vitamin D is associated with longer survival after diagnosis of the disease.

Professor Giovannucci reckons that a supplement of 1,500 international units (IUs) of vitamin D per day may reduce the risk of cancer by 17 per cent, and that the risk might be reduced even further by higher levels of vitamin D. Cancers of the digestive system, which include cancer of the pancreas, are most sensitive to vitamin D, and Professor Giovannucci calculated that they might be reduced by 43 per cent if everyone took a 1,500 IUs vitamin D supplement daily. Carefully regulated regular sunbathing without sun cream might also help (see box).

Doctors knowledgeable about vitamin D believe that it may be effective in treating cancer because laboratory work backs up the survey findings. Vitamin D is active in more than 30 different tissues of the body, where it induces cells to complete their development and enables cells that have developed wrongly to die off instead of forming a tumour.

So, if I had cancer, or if a friend asked me whether there was anything else he or she could do to improve the chances of living longer, I would say: take vitamin D. It is worth a go. You have nothing to lose. At the very least, it is likely to make you feel a bit better and improve your general health, because three quarters of the UK population have less than optimum levels of the vitamin. And scientific evidence suggests that vitamin D may also help your body to fight the cancer itself.

Vitamin D: are you getting enough?

Very large doses of vitamin D can be taken safely by a healthy person. Anyone with cancer who wants to take vitamin D should, of course, discuss it with their doctor. There could be special reasons for caution. Vitamin D should never be taken as an alternative to conventional treatment.

Vitamin D should not be taken by anyone with kidney stones, hypercalcaemia, hyperparathyroidism, or by anyone taking Dyazide diuretics. Nor by anyone with sarcoidosis, any granulomatous malignancy such as lymphoma, oat-cell lung cancer, or when cancer has spread to the bone.

How much vitamin D should someone with cancer take? Official advice in the US is that up to 2,000 IUs per day is safe for a person in normal health. However, researchers into vitamin D have calculated that a person needs between 3,000 and 6,000 IUs per day for optimum health. .

Unfortunately, vitamin D in this strength cannot be obtained in the UK, but it can be bought from Freeda Vitamins ( www.freedavitamins.com), or from the Life Extension Foundation ( www.lef.org/about). For information on dosage of vitamin D and safety, consult the Vitamin D Council website ( www.vitamindcouncil.com), and for more information about vitamin D and chronic disease, visit: www.healthresearchforum.org.uk. Sunlight is the natural source of vitamin D and it's free. But anyone who has had radiotherapy should avoid exposing sensitive skin to the sun. Drugs may cause photosensitivity, so, if having chemotherapy, consult your doctor about sunbathing and be cautious to begin with. If in doubt, test a small patch on one arm or leg first.

In the UK, in midsummer, around midday, expose each side of the body for three to five minutes without sun cream to begin with - longer at other times or if cloudy. Gradually increase day by day, until exposing each side for up to half an hour. It is important to avoid the burning that causes peeling or blistering. Some pinkness after exposure is not uncommon and need not be a worry. Use a hat to avoid over-exposure of the face.

When abroad, expose your skin for shorter times than in the UK, and increase exposure slowly. Be especially careful in the middle of the day. In northern Europe, the sun is only strong enough to make vitamin D from mid-April to the end of September. Take a vitamin D supplement in winter, or, better still, all year round.