Results from a large new study do show that the higher a woman’s vitamin D level, the lower her risk of developing multiple sclerosis (MS). This isn’t the first study to suggest a link between vitamin D and MS, but it is by far the largest. Researchers from the Harvard T.H. Chan School of Public Health looked at data from thousands of pregnant women in Finland who had provided blood samples and measured the amount of vitamin D in them.
We’ve known for some time that MS is more prevalent at higher latitudes, where sunlight is less intense for much of the year. The new findings strongly suggest that vitamin D, which the body synthesizes in response to sun exposure, plays a protective role.
MS begins as localized inflammatory damage to the myelin sheaths that surround nerve fibers as a result of immune system attack. Although MS is considered an autoimmune disease, it is not clear what triggers it. MS occurs two to three times more often in women than in men, and while it affects all ethnic groups, it is most common among Caucasians, particularly those of northern European ancestry. It is usually diagnosed between ages 20 and 40, but can occur at any age. Risks are higher among those who have a close relative with the disease.
The Harvard study found that MS is twice as frequent among women who are deficient in vitamin D compared to those whose level was considered adequate and that women with an “insufficient” level had a 27 percent higher risk.
The investigators defined an adequate vitamin D level as 50 nmol/L (nanomoles per liter) or greater, insufficient as falling between 30 and 50 nmol/L, and deficient as less than 30 nmol/L.
Compared to women whose vitamin D level ranked in the top fifth, those in the bottom two fifths had a 53 to 66 percent increased risk of MS.
Commenting on the findings, lead researcher, Dr. Kassandra L. Munger, noted that it isn’t clear what the optimal level of vitamin D would be to prevent MS or if supplementation is advisable. However, in an editorial accompanying publication of the study, Ruth Ann Marrie, M.D., Ph.D. of the University of Manitoba and Christopher A. Beck, Ph.D. of University of Rochester Medical Center, wrote, “It is time to take an active approach to preventing MS, at a minimum targeting those individuals with an elevated risk…including smokers, the obese, and those with a family history of MS”. They also noted that doses of vitamin D up to 4,000 IU/day are safe for adults, even in pregnancy. I recommend that everyone take at least 2,000 IU of D3 (the form better utilized by the body) for optimum health.
Andrew Weil, M.D.
Kassandra L. Munger et al, “25-Hydroxyvitamin D deficiency and risk of MS among women in the Finnish Maternity Cohort.” Neurology, September13, 2017, doi: