Multiple Sclerosis and Vitamin D

I have commented before that the increasing rates of multiple sclerosis as we move away from the equator has lead to speculation that it might have something to do with lack of sunlight and therefore reduced production of vitamin D in the skin.

A lack of vitamin D may also explain the increased rates of both type 1 and type 2 diabetes, as well as cluster headache at higher latitudes.

Vitamin D is not a single vitamin, but is instead a group of fat-soluble prohormones as well as the metabolites and analogues of these substances. There are two major forms of vitamin D: D₂ (or ergocalciferol) and D₃ or cholecalciferol. Vitamin D₃ is produced in skin exposed to sunlight, specifically ultraviolet B radiation. Very few foods are naturally rich in vitamin D, and most vitamin D intake is in the form of fortified products including milk and cereal grains.

It used to be that we all made plenty of Vitamin D simply by being outside in the sun, but our time outside has been steadily falling since the beginning of the Industrial Revolution, and there are the increasing concerns about exposure to sunlight and some skin cancers.

Vitamin D is involved in many critically important chemcial reactions in the body, and Vitamin D receptors are found in cells in most organs in the body, including the brain, heart, skin, gonads, prostate, and breast. Apart from its effects on regulating calcium and phosphorus, Vitamin D is involved in maintaining the integrity of cell membranes and in modulating the immune system. There is some evidence that a modest increase in Vitamin D intake may reduce the risk of colon, breast and ovarian cancers.

There is a risk of overdosing with Vitamin D. The U.S. Dietary Reference Intake
Tolerable Upper Intake Level (UL) of vitamin D for childern and adults
is 50 micrograms/day (2000 IU/day). In adults, a daily intake of 2500
μg/day (100,000 IU) can, over a period of weeks and months, produce toxicity  and, if
taken for years, as little as 50 to 75 μg/day (2000 to 3000 IU) can
produce toxicity.

In this week’s issue of the Journal of the American Medical Association, there is an important report that endorses everything that we have been saying. Researchers from
several prominent institutions in the United States have examined the
hypothesis that higher levels of 25-hydroxyvitamin D are associated
with a lower risk of multiple sclerosis.

The study confirmed the hypothesis: the risk of multiple sclerosis (MS) fell as blood levels of the vitamin rose.

The researchers uncovered 257 cases of MS among more than seven million military personnel who had given blood samples to the US Department of Defense.

Amongst white personnel, there was a 41% decrease in MS risk for every 50 nanomoles per litre increase in 25-hydroxyvitamin D, the key form of the vitamin found in the blood.

Those whose vitamin level was in the top 20% had a 62% lower risk of MS than those whose level was in the bottom 20%.

The researchers found no such association among black and hispanic personnel, but this could be a reflection of the smaller size of these sample groups.

This new research ties in with other work that has shown that Vitamin D supplements can prevent or favourably affect the course of a disease similar to MS in mice, as well as evidence that if you live in the Northern Hemisphere, being born in May is associated with a lower risk of MS than if you were born in the winter. If you are born in May, your mother will probably have been exposed to more sunlight – and therefore have produced more Vitamin D – during the later part of pregnancy when the final development of the nervous system takes place. Or alternatively you may have had a heathy dose of sunlight in the weeks immediately after your birth.

It is most likely that the Vitamin D helps by modulating the immune system and suppressing autoimmune reactions caused by specialised T helper 1 cells attacking myelin, the insulating material that sheathes most nerves. It is these attacks that are thought by most experts to play a key role in the development of MS.

If confirmed, the finding suggests that many cases of MS could be prevented or its severity reduced by increasing our levels of Vitamin D.

The data also confirm a point that we have made before: we should not be aiming to "boost" our immune systems, but to "modulate" them.

If you see an advertisement for some potion that is supposed to boost your immune system to help you ward off colds, the flu or something more serious, be suspicious: if the seller does not know the  difference between boosting and modulating, it would be best to move on.