Interdependence and contributions of sun exposure and vitamin D to MRI measures in multiple sclerosis
Background: Vitamin D and MS
Recent studies have illustrated a relationship between levels of vitamin D and multiple sclerosis disease activity as seen through clinical and MRI measures. Aside from its role in promoting calcium absorption and overall good bone health, vitamin D has also been shown to have a direct effect on the immune system. The immunoregulatory function of vitamin D, including its ability to inhibit T and B cell activity, has prompted ongoing research into its impact on disease course and treatment of autoimmune diseases like MS.
The human body is able to produce vitamin D with the help of sufficient exposure to UVB-radiation. Natural human levels of vitamin D are therefore dependent on factors such as: amount of sun exposure, use of sun protection, geographical location, skin colour, age, sex, and genetic factors. A person’s level of vitamin D can also be increased through intake of vitamin D-enriched foods and supplements.
Several lines of evidence have reported associations between vitamin D with relapse rates, changes in disability, and risk of MS. The goal of this study was to assess the relative contribution of environmental factors such as sun exposure and vitamin D supplementation to vitamin D levels in people with MS. The study also aims to ascertain the relationship between sun exposure and MRI measures of neurodegeneration.
The study, led by a team of scientists from the Department of Neurology at the State University of New York in Buffalo, included 264 people with MS and 69 healthy controls. Subjects underwent neurological and MRI examinations and provided blood samples. Information on race, skin and eye colour, supplement use, body mass index (BMI) and sun exposure history was obtained through a questionnaire. Levels of vitamin D were measured using mass spectrometry.
What they found:
Results of the study revealed that vitamin supplementation, sun exposure, eye colour and BMI were associated with changes in vitamin D levels in people with MS. The study also showed that longer sun exposure was associated with a significant increase in brain volume in people with MS compared to healthy controls. The researchers speculate that changes in the immune system resulting from exposure to the sun may lead to changes in brain volume and other MRI measures of MS. The main limitation of their research was that it was a cross-sectional study, meaning that the investigators are collecting information from the subjects at a specific point in time. This may lead to past lifestyle changes having an effect on the results observed.
This study adds to the growing body of research that highlights the relationship between vitamin D and MS. Although research on vitamin D has shown that its effect on the immune system bears implications in reducing disease severity, it is important to keep in mind that the results are not conclusive. Thus, further research in this area as well as on the therapeutic benefit of vitamin D is required.
Source: Zivadinov R et al. Interdependence and contributions of sun exposure and vitamin D to MRI measures in multiple sclerosis. Journal of Neurology, Neurosurgery & Psychiatry, 2013 Feb 5 [Epub ahead of print]