Australian researchers have provided important evidence about the value of maintaining a high vitamin D level for people with MS.
In a prospective study as part of the Southern Tasmanian Multiple Sclerosis Longitudinal Cohort Study, published in the Annals of Neurology, they followed 145 people with MS for an average of 2.3 years. Many of the cohort were taking vitamin D supplements, although surprisingly most of these were taking a dose below 400 IU/day, and supplementation did not have a significant effect on vitamin D levels as expected.
The important findings were that for every 10 nmol/L higher the vitamin D level in blood, there was a 12% reduction in the risk of relapse. This effect was linear, that is, the benefit did not seem to reach a threshold level over which there was no additional benefit.
I have reproduced the graph from the paper of the risk of relapse against the vitamin D blood level. It can be seen that there is essentially a straight line relationship between risk reduction and increasing vitamin D levels.
If the line is continued down to no risk, it intersects at a vitamin D level of around 150 nmol/L, confirming the message on this website, that it is critical for people with MS to keep their vitamin D levels above 150 nmol/L year round.
This is strong evidence supporting the value of maintaining a high vitamin D level for people with MS. The study further showed that for most people in Tasmania, the level was related to time outdoors and physical activity, and this is the ideal way of obtaining vitamin D.
The study did however show that on average, the whole group was vitamin D deficient during winter, and that is the reason we advocate vitamin D supplementation during winter with adequate doses of vitamin D (at least 5,000 IU a day).