A new research study has linked low vitamin D with increased risk of multiple sclerosis (MS). The study found that four genetic variants carried by individuals predispose them to have lower vitamin D and also have a higher risk of multiple sclerosis. This link was something that has been long suspected but until today difficult to prove.
The research paper was published today, August 27, in PLoS Medicine. The scientists explain that their findings show individuals carrying certain genetic are more predisposed to having lower vitamin D and a higher risk of multiple sclerosis. In people suffering of this chronic disease, their immune system attacks the nervous system.
The hypothesis that low vitamin D and multiple sclerosis are linked has been long-standing, based on previous studies that compared the risk of multiple sclerosis with people's vitamin D levels. However these studies have merely suggest at best an association that could have been actually caused by other factors and not necessarily show that low vitamin D causes multiple sclerosis, according to co-author of the latest study, Dr. Brent Richards, associate professor at McGill University in Montreal.
Dr. Richards explains for the Australian Broadcasting Corporation that the problem with the previous studies is that they are quite likely to be confounded because people who use supplements show that they are paying attention to their health and often undertake other healthy behaviours.
According to Dr. Richards, vitamin D levels may also be related to multiple sclerosis through reverse causation, because people suffering of this chronic medical condition may tend to spend more time indoors, which further decrease their vitamin D levels.
To avoid confusion in their results, the research team used data from an earlier study conducted on nearly 34,000 people. The research looked for genetic markers of low vitamin D and has found four genetic variants. Scientists compared the results with those of 24,000 controls and another group of nearly 14,500 people with MS.
They conclusion of the study is that individuals who were been vitamin D deficient and having any one of these genetic markers were much more likely to have multiple sclerosis. The study was based on a method called Mendelian randomization, that ensures to leave out the possibility that the effect is related to lifestyle factors, according to Richards.