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Vitamin D status significantly affects risk of multiple sclerosis among Finnish women

Posted on: November 10, 2017   by  Riley Peterson & John Cannell, MD.


Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system (CNS) which disrupts the flow of nervous signals between the brain and spinal cord to the rest of the body. Symptoms of this condition are variable, and it is likely that no two MS patients will have the same symptomatic experience. Symptoms may include fatigue, weakness, numbness or tingling, cognitive impairment, pain, vision loss, depression and more.

Though the cause of MS is still unknown, a combination of environmental, genetic, infectious and immunological factors are thought to contribute to the onset of this condition. Additionally, an abundance of research has observed a relationship between multiple sclerosis and vitamin D status. Currently, this research supports the following:

However, few studies have assessed factors that may impact future risk of MS in a healthy population. Therefore, researchers chose to evaluate a large cohort of Finnish women in order to determine if vitamin D deficiency is considered a risk factor for MS in this population.

This study included women who had participated in the Finnish Maternity Cohort (FMC).  Beginning in 1983, this cohort analysis included over 800,000 pregnant women who had their serum 25(OH)D status tested between 10-14 weeks of gestation. The researchers from this study identified 1,092 women who were clinically diagnosed with MS between 1983 and 2009 and 2,123 age and location matched controls.

Serum vitamin D levels were available in all individuals, prior to diagnosis in the MS group. For those who participated in the FMC over the years and had several vitamin D tests administered, these levels were averaged. Additionally, season of the blood draws were recorded to use in a multivariate analysis. Vitamin D levels below than 12 ng/ml (30 nmol/l) were considered vitamin D deficient, between 12-20 ng/ml (30-50 nmol/l) was considered insufficient, and levels above 20 ng/ml (50 nmol/l) were considered sufficient.

This is what the researchers found:

  • More than 50% of participants were vitamin D deficient, over 33% of participants had insufficient levels, only 0.04% had 25(OH)D levels above 30 ng/ml (75 nmol/l), and of these, only 0.0009% had levels above 40 ng/ml (100 nmol/l).
  • A 20 ng/ml (50 nmol/l) increase in vitamin D status was associated with a 39% reduced risk of 95% CI 0.44–0.85, p = 0.003).
  • Compared to those with levels less than 20 ng/ml (50 nmol/l), women with levels less than 12 ng/ml (30 nmol/l) had a 43% increased risk of MS.
  • Compared to participants with insufficient levels, deficient women had a 27% increased MS risk (95% CI 1.07–1.50, p = 0.005).
  • Women with the lowest levels of vitamin D had a 53%– 66% increased risk of MS compared to women with the highest levels of vitamin D (p < 0.001).

The researchers concluded:

“Our results further support and extend those of previous prospective studies of 25(OH)D levels in young adults and risk of MS, and suggests that many individuals are exposed to an increased MS risk that could be reduced by broad population-based programs to prevent vitamin D deficiency.”

There were both some strengths and weaknesses of this study that should be mentioned. A few strengths of this study include the large sample size and the use of a control group. It is important to use a control group in order to be able to compare the effect of vitamin D status in a healthy population against vitamin D status in a population with a specific disease or health condition. Also, the researchers were able to collect vitamin D status an average of 9 years prior to MS diagnosis, which limits the effect of reverse causation.

Despite these strengths, there were some limitations as well. The researchers noted they did not account for confounders such as body mass index in early life, Epstein-Barr virus infection, smoking and human leukocyte antigen status, all of which are risk factors for MS. Additionally, this population was comprised of mainly Caucasian women, which limits the generalizability of these results.

Research seems to support that higher vitamin D status is beneficial for this population. Due to the fact that vitamin D supplementation is an inexpensive and safe way to ensure your vitamin D status is within healthy range, the Vitamin D Council recommends supplementing with between 5,000-10,000 IU per day.

We asked Dr. Cannell to weigh in on this study. He replied,

“As we point out, virtually none of these women had the levels recommended by the Endocrine Society [>40 (not 30) ng/ml]. This almost certainly means this study underestimates the protective effect of vitamin D levels on MS.”

He continued,

“What vitamin D level maximizes the protective effect of vitamin D on MS? My personal experience with another autoimmune illness (autism), is that higher levels of vitamin D has been more beneficial (i.e 40 ng/ml is more beneficial than 30 ng/ml, 50 ng/ml is more beneficial than 40 ng/ml, etc. up to about 70 or 80 ng/ml). While I have not supplemented autistic children above 80 ng/ml, it is possible that the therapeutic effect of vitamin D is not maximized until levels are substantially above 100 ng/ml. Remember, as Michael Holick says, toxicity has never been convincingly demonstrated at levels less than 200 ng/ml.”

As always, we are here to answer any questions you may have about vitamin D supplementation, sun exposure and health. Please email [email protected] for all questions and concerns.


Peterson, R. & Cannell, JJ. Vitamin D status significantly affects risk of multiple sclerosis in a cohort of Finnish women. The Vitamin D Council Blog & Newsletter, 10/17.


Munger, K. et al. 25-Hydroxyvitamin D deficiency and risk of MS among women in the Finnish Maternity Cohort. Neurology, 2017.

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