Sunlight and enhanced vitamin D levels are associated with a reduced risk of a wide range of chronic diseases including multiple sclerosis (MS). This condition in characterised by degradation in the fatty coverings of nerves in the brain and spinal column. These fatty coverings are known as ‘myelin sheathes’, and so the process of degradation is often referred to as ‘demyelination’.
Previous research into the link between sunlight/vitamin D and MS has focused on individuals with established disease. The evidence does show a significant link here, but we cannot assume from this evidence that low sunlight/vitamin D levels cause MS. It might be, for instance, that individuals with MS get less sunlight exposure and therefore have lower vitamin D levels because of disability associated with their condition. In other words, maybe the MS causes low vitamin D levels, not the other way round.
Today saw the publication of a study in the journal Neurology that appears to have added some clarity to this picture. It looked at the relationship between sunlight exposure and vitamin D levels in individuals with the very first signs of MS – referred to as the ‘first demyelination event’ of FDE [1]. The thinking here is that if there exists a relationship between FDE and low sunlight/vitamin D, then this is unlikely to be due to disability (and therefore reduced sunlight exposure) associated with MS. More likely, therefore, is that the low sunlight exposure/vitamin D is causing the MS.
The results of this study showed that those reporting the most sunlight exposure over their lives (from age 6) were at a significantly reduced risk of a FDE. Self-reported sun exposure is prone to some error, and the researchers also checked sunlight exposure more objectively by assessing evidence on skin damage from sun exposure. Here again, those with the most evidence of damage had the lowest risk of a FDE. Higher vitamin D levels were also associated with a reduced risk of a FDE.
The demyelination characteristic of MS is essentially an ‘autoimmune’ issue – where the body’s immune system reacts against its own tissue. Vitamin D has been shown to help dampen the immune response characteristic in MS.
However, there is also evidence that sunlight helps protect against MS in ways that actually have nothing to do with enhanced vitamin D production (see here for more about this).
For more on how to get safe and beneficial sunlight exposure during the warmer months, see here.
References:
1. Lucas RM, et al. Sun exposure ad vitamin D are independent risk factors for CNS demyelination. Neurology 2011;76(6):540-548
