Low Vitamin D Levels Associated with MS Susceptibility

MS prevalence increases in areas of higher latitude with decreased levels of sunlight exposure.

A recent study aimed to further evaluate the relationship between vitamin D deficiency and multiple sclerosis (MS). While previous studies have been conducted and have established this relationship, the question of causality still remains.

MS is a debilitating disease that mainly affects young adults, with a mean age for diagnosis between 28 and 31 years. Epidemiological studies have shown the prevalence of MS to be in areas of higher latitude with decreased levels of sunlight exposure.

This fact alone has led many scientists to question whether or not vitamin D levels within the body affect one’s susceptibility to the disease. Further evidence to support the vitamin D hypothesis arose from the Nurses’ Health Study, which reported a protective effect on MS for women who had high levels of daily vitamin D intake.

Lower levels of vitamin D have also been associated with higher rates of relapse in MS and higher levels of disease activity and disability. To test this causal relationship, scientists first ascertained the level of 25-hydroxyvitamin D (25OHD, the clinical determinant of vitamin D status) among participants in the study of 4 single nucleotide polymorphisms (SNPs) that were associated with 25OHD level in a genome-wide association study (SUNLIGHT).

The researchers then used the SNPs to see if there was an association between genetically reduced 25OHD level and susceptibility to MS. The scientists found through their investigation that a natural-log-transformed 25OHD level by one standard deviation was associated with a 2-fold increased risk of MS.

This finding suggests that by increasing one’s 25OHD level by approximately 1.5-fold decreases their chances of developing MS by 50%. Although the study holds much promise in furthering the understanding of the relationship between vitamin D levels and susceptibility to MS, the study approach largely avoids the possibility of confounding or reverse causation.

Therefore, the reliability of these findings may be limited by some of the assumptions made by the researchers during their analysis. Moreover, while these findings support a role for vitamin D in MS susceptibility, it does not evaluate the role of vitamin D in modulating the course of MS after its onset.

Additionally, as the study only had participants of European descent, the findings may not apply to persons of other origin. Nevertheless, the findings support the need for randomized controlled trials to be conducted in order to investigate whether or not vitamin D supplementation can prevent the onset and/or progression of MS.

With further studies, the details of this relationship will be revealed and patients may have more methods of prevention and treatment as a result.