There is now so much evidence of a protective effect of adequate vitamin D levels against developing MS that one has to wonder why scientists don't just get on with the large scale randomised trials to show vitamin D supplementation actually works in preventing MS.   

To the credit of MS Australia, it has embarked on a very large Australian study to do just that in people who have had a single demyelinating event (clinically isolated syndrome [CIS]) that is not yet diagnosed as MS. Even more impressively, they have at last chosen to use adequate doses, with one of the groups receiving 10,000IU a day. But in this study, Swedish researchers have provided more proof of the protective effect of adequate vitamin D levels.

They studied a massive sample of people who had provided blood specimens in Sweden since 1975, but only 192 in fact had MS. They used a case-control study design, matching these 192 people with twice the number of people without MS who had also provided samples, and compared vitamin D blood levels prior to the diagnosis of MS.

There were a couple of disturbing findings, most particularly that the average level in blood in winter for the population was around 30nmol/L, a staggeringly low level that predisposes this population not only to MS, but also to a range of other diseases, including type 1 diabetes and rheumatoid arthritis.

Further, they found that the average blood level of vitamin D had been steadily dropping since 1975, and hypothesised that this might be the reason for the explosion in MS incidence in that part of the world.

As far as risk of MS goes however, they found that a blood level of 75nmol/L or above was highly protective against the development of MS, reducing the risk by 61%. At OMS we recommend 100nmol/L based on previous work, and this paper does not change that view.

They simply did not have enough numbers of people with high enough levels of vitamin D to make any conclusion about whether a higher level would be even more protective.

One other disappointing finding was that they couldn't find any protective effect of adequate vitamin D levels in pregnancy on the risk of the baby later developing MS, but almost certainly, that again was due to inadequate numbers.

For people with MS, this study reinforces the need to supplement our children with vitamin D, and we continue to recommend a pro-rata dose based on 5,000IU a day for an adult (based on an adult weight of 50kg, so for a 25kg child, 2,500IU a day), which for most people raises levels to 100nmol/L or above. The level of around 2,000IU a day suggested in this paper is too low.