Scientists have long wondered if there is a causal relationship between ultraviolet (UV) light exposure from the sun and the incidence of multiple sclerosis (MS). The reason for this is because MS occurs with greater frequency in the northern regions of the planet than in the tropics, where sunshine is much more prevalent. With this in mind, researchers have also wondered if levels of vitamin D, the sunshine vitamin, might be a factor in the initiation and severity of MS.

Now, a recent paper published in the Proceedings of the National Academy of Science suggests that UV light may in fact play a more larger role than previously believed in controlling MS. The reason for this is because MS is a neurological disorder that results from the body’s own immune system attacking the nerves. Both vitamin D and UV light are believed to regulate the immune system, and could potentially play a role in limiting the onset of MS.

The question then becomes, does the UV light directly affect immune regulation, does it accomplish it through the production of vitamin D, or both? While it has been observed in animal models that high doses of vitamin D can block MS, it results in high levels of serum calcium which some experts deem as unacceptable. Furthermore, people living in equatorial regions, where there is abundant sunshine, do not have high levels of calcium in their blood, and yet have low rates of MS. In light of this, some experts believe that there are factors other than vitamin D at play.

Researchers set out to answer this question by employing specially designed animals models that were particularly susceptible to an MS-like disease. By triggering the disease and then exposing them to differing levels of UV radiation, they observed that exposure to UV light (the equivalent of 2 hours of sunlight) did not change the rate at which the disease occurred. However, it reduced the symptoms of MS, especially when UV light exposure was fairly regular, i.e., every other day.

Interestingly, while the exposure time did affect the production levels of vitamin D, the authors of the study noted that this alone could not explain the protective effect as seen in the reduction in MS symptoms. They suggest that other compounds my be produced by the skin, but acknowledge that they do not really know what is behind the phenomenon, and further studies need to be done. In light of this, no revised guidelines regarding UV light exposures can be suggested at this time.

MS is a progressive neurological disorder that results in our body’s immune system destroying the protective coating (myelin sheaths) around our nerves. As a result, the nerves are unable to transmit electrical impulses, and can lead to their complete and irreversible degradation. The disease is more common in young people, particularly young women.

The exact causes are unknown, but genetics and illness are believed to play a role. Risk factors include age (20 to 40 years of age), gender, heredity, and geographical location, with the risk increasing with increasing latitude. Interestingly, if a child changes location before puberty, his or her risk level for MS aligns with that of their new location.

For more information about MS, visit the homepage for the National Multiple Sclerosis Society.