Professor Michael Hutchinson, Consultant Neurologist at St Vincent's Hospital and MS Ireland's Medical Advisor discusses the relationship between Vitamin D and multiple sclerosis (MS). Professor Hutchinson is responding to the recent report on BBC News which looked at a study that questions the role of Vitamin D in MS and chronic diseases.
It is not surprising that the association of a low vitamin D with a number of chronic diseases is not causal in the sense that the low vitamin D level is the cause of the chronic disease. Rather, the reverse is more probable; having a chronic disease results in a low vitamin D level. The reason for this is that people who are chronically ill tend not to expose themselves to the sun, the major source for vitamin D, and may have a reduced intake of a number of foods which contain vitamin D. We are aware of this phenomenon in relation to multiple sclerosis. For example patients who have significant disability due to secondary progressive multiple sclerosis or primary progressive multiple sclerosis have low vitamin D levels because they cannot get out and about and expose themselves to sunshine. This has been noted in a number of epidemiological studies of vitamin D levels in people with multiple sclerosis.
Vitamin D deficiency: an environmental factor in multiple sclerosis
There is a significant environmental factor in relation to the pathogenesis of multiple sclerosis. This has been evident from immigration studies over the last 40-50 years. These studies showed that emigration of United Kingdom citizens to South Africa from the United Kingdom before the age of 16 years protected individuals from the high risk of multiple sclerosis pertaining to the UK. These individuals are acquired the much lower risk of MS in the white population of South Africa. Similarly multiple sclerosis is very uncommon in the native population of the West Indies, however following the migration of a large number of West Indian people to the United Kingdom in the 1950s, it has been observed that multiple sclerosis rates in the children of these 1950s immigrants has risen considerably. The only thing that would explain this is a change in the environment.
Perhaps even more persuasive is the observation that multiple sclerosis is seven times more common in Hobart, Tasmania than in Queensland in Northern Australia. The Australian population is predominantly white and of European ancestry. The marked difference in the incidence and prevalence of multiple sclerosis between Tasmania (40° south) and Northern Queensland (10°south) can only be explained by environmental factors and the main candidate is sunshine exposure and vitamin D level.
Therefore in discussing the relationship between vitamin D and multiple sclerosis, we are using very powerful epidemiological evidence.
How do we prove that vitamin D deficiency is a significant factor in disease susceptibility and disease activity in multiple sclerosis?
The main aim at present is to prove that treatment with vitamin D in large doses will prevent the development of multiple sclerosis in patients presenting with a first clinical symptom. We at St Vincent's University Hospital had proposed such a trial several years ago, however we were not able to obtain funding for it. It was therefore with delight that I learned that French government health research funding has been made available to French neurologists to perform such a study, called the "D-LAY Study". The first patients have been recently recruited; it will be approximately 3 years before we will know the result. Similarly in Australia/ New Zealand the multiple sclerosis societies have funded a study (PREVANZ study) in which patients with a first symptom of multiple sclerosis, the clinically isolated syndrome, are randomised to one of four treatment groups: placebo, vitamin D 1000 international units daily, vitamin D 5000 units daily, or 10,000 units daily. Again this study will not be reporting for several years. In St Vincent's University Hospital we examining, in a small phase 2 study, the immunological effects of treating patients with vitamin D when they present with the very first symptom of multiple sclerosis.
There is no doubt that the epidemiological evidence implicating vitamin D deficiency in susceptibility to multiple sclerosis and in relation to disease severity/activity is very strong. What we need to do now is prove it in randomised controlled trials; two of these trials are presently underway.