French researchers publishing in the world's premier neurology journal Brain, have summarised the role of low vitamin D levels as a risk factor for multiple sclerosis. They note that, in addition to its primary role in calcium metabolism, vitamin D has anti-inflammatory, anti-infectious, immunomodulatory, and anti-cancer properties, and acts as a neurotransmitter involving many autoimmune diseases including, among others, multiple sclerosis, type 1 diabetes, rheumatoid arthritis and lupus.

They conclude that all the different types of research on vitamin D in MS have reached consistent conclusions, and have 'already allowed us to reach a global level of evidence that should be considered important'.  In other words, it is time to stop investigating whether low vitamin D plays a key role in MS, simply accept that the evidence clearly shows it does, and get on with the clinical trials of its supplementation.