Summer sun prevents multiple sclerosis

April 10, 2007

Still more supports the theory that vitamin D can prevent multiple sclerosis. Enjoy the sun while its there.

Multiple sclerosis (MS) is a feared disease. Many believe that sclerosis is synonymous with a life in a wheelchair, and many have heard about tragic examples of how the disease can progress. It is worth remembering that even 20 years after the emergence of the disease, 75% of patients can walk unaided. Also, the death rate for those suffering from sclerosis is not much higher than that of the rest of the population.

On the other hand, MS affects especially younger people, primarily women. It is disquieting that the frequency of this disease has increased in the last 50 years and continues to increase. Over 80,000 people in the UK suffer from MS, which at a prevalence of over 140 people per 100,000 the highest in the industrialised world.

MS is an “autoimmune” disease, which is to say a disease where the body’s immune system turns against the body itself. In the case of MS the so called myelin sheaths which coat and isolate the nerves are attacked. On average, every fourth person with MS also suffers from another autoimmune disease, for example psoriasis, arthritis, or metabolism diseases.

Can one prevent MS? It is tempting to have this thought when one notices the enormous geographic variations. In England, Denmark, Norway, Sweden, Finland, Germany, and Canada the frequency is about the same. In Greece and Turkey it is about half as common while in northern Spain and Italy the frequency lies in between that of these areas.

These and other figures support a growing belief that MS has something to do with lack of sunlight; or more accurately, lack of vitamin D, of which the sun is the most important source. Vitamin D has in studies prevented an experimental form of MS (EAE, Experimental Autoimmune Encephalitis). In countries north of a latitude of 42, corresponding to Corsica, the sun is so low during the winter months that vitamin D practically cannot be produced in the skin. The result is widespread vitamin D deficiency.

Less than half the risk
Researches from Harvard University among others analyzed the problem in more detail. They studied 257 blood tests from military personnel who contracted MS between 1992 and 2004. The blood tests were taken and frozen before these people became sick. The question was whether they had remarkably little vitamin D in their blood when compared to people who did not contract MS.

It was shown that they did. 25-OH-D, the best measure for vitamin D status, was measured in both the sick and a large number of healthy people who were randomly chosen from 7 million personnel. It was found that “high circulating levels of vitamin D are associated with a lower risk of multiple sclerosis.” Low vitamin D levels were especially risky for people under 20 years of age.

How much vitamin D is enough? When the level of 25-OH-D was at least 99 nannomol/litre serum, the risk of MS was the lowest at about 40% average. The difference was statistically certain. For comparison, levels under 50 are indicative of insufficient levels of vitamin D. Such values can be found in most people during the winter.

The theory that vitamin D prevents MS is thus strengthened. One should attempt to distance oneself from vitamin D deficiency. This is easy during the summer, but from October to April it requires, for the majority of those in our latitudes, supplements.

By: Niels Hertz MD

1. Munger L et al. Serum 25-Hydroxyvitamin D levels and risk of multiple sclerosis. JAMA 2006;296:2832-2838.
2. MS prevalence data for selected countries:
3. Newsletter from Vitalrådet dec. 27. 2006