For the first time, concrete evidence has been found that vitamin D deficiency increases the risk of multiple sclerosis. Jagdeep Worah reports

For the first time, concrete evidence has been found that vitamin D deficiency increases the risk of multiple sclerosis, especially in individuals whose genetic structure makes them more vulnerable to MS.

A UK and Canadian team found that vitamin D helps to control a gene known to increase MS risk, according to their report published in the PLoS Genetics journal.

The study suggests that vitamin D supplements taken during pregnancy and early in life could prevent the disease. It is caused by the loss of nerve fibres and their protective myelin sheath in the brain and spinal cord, resulting in neurological damage.

Earlier research had indicated that both genetic and environmental factors play a role in MS, a condition that affects 2.5 million people worldwide. The 'environmental factor' is mainly vitamin D, known as the 'sunshine vitamin' because it is naturally produced in the body by exposure to sunlight. There is evidence that populations from Northern Europe have a higher increased risk of developing MS if they live in areas receiving less sunshine.

In the latest study, researchers at the University of Oxford and University of British Columbia looked at a section of the genome on chromosome six which had been shown to have the strongest effect on MS risk.

While one in 1,000 people in the UK is likely to develop MS, this number rises to around one in 300 among those carrying a single copy of the gene variant - known as DRB1*1501 - and one in 100 for those carrying two copies.

The researchers found that proteins activated by vitamin D in the body bind to a particular DNA sequence next to the variant gene, in the chromosome six region, altering its function. They believe that vitamin D deficiency in mothers or even in a previous generation may lead to altered expression of the gene in their offspring.

Exactly how the gene-environment interaction alters MS risk is yet to be determined; one explanation could be an effect on the thymus - a part of the immune system which produces T cells to attack invaders such as bacteria and viruses.

It is thought that in people who carry the gene variant, a lack of vitamin D during early life might impair the ability of the thymus to delete rogue T cells, which then go on to attack the body, leading to a loss of myelin on the nerve fibres.

The researchers believe that vitamin D deficiency in mothers or even in a previous generation may lead to altered expression of DRB1*1501 in offspring. Hence it is considered extremely important for expectant mothers to take vitamin D supplements.

The study was funded by the MS Society in the UK, the MS Society of Canada, the Wellcome Trust and the Medical Research Council, researchers at the University of Oxford and the University of British Columbia.

Co-author Prof George Ebers, from the Wellcome Trust Centre for Human Genetics at the University of Oxford, said it had been known for a long time that genes and the environment determine MS risk. "Here we show that the main environmental risk candidate - vitamin D - and the main gene region are directly linked and interact."

Co-author Julian Knight said in a journal news release, "In people with the DRB1 variant associated with MS, it seems that vitamin D may play a critical role. If too little of the vitamin is available, the gene may not function properly."

Study leader Dr Sreeram Ramagopalan added, "Vitamin D is a safe and relatively cheap supplement with substantial potential health benefits. There is accumulating evidence that it can reduce the risk of developing cancer and offer protection from other autoimmune diseases." Among other food, milk is considered a good source of vitamin D.

Experts hail breakthrough
Simon Gillespie, chief executive of the MS Society in the UK, said, "These remarkable results tie together leading theories about the environment, genes and MS, but they are only part of the jigsaw. The discovery opens up new avenues of MS research, and future experiments will help put the pieces together."

Politicians in the UK hailed the first scientific research linking the causes of multiple sclerosis with vitamin D deficiency as a giant leap forward, and called for the work to be carried forward, even as health food shops in Scotland were reported to show increased sales of vitamin D supplements.

Ross Finnie MSP, the Liberal Democrat health spokesperson, described the research as a giant leap forward in our understanding of MS, giving hope of a cure. Richard Simpson, the Labour health spokesman, said: "This is a really interesting piece of research and an exciting finding. Further progress in Prof Eber's work could lead to a genuine breakthrough, which may help prevent MS in future generations. It is important that the chief scientist supports this work."

Power supplement
The scientific breakthrough comes after a groundswell of expert belief in the importance of vitamin D. Scientists from the World Health Organisation had earlier told officials from the UK health department that there should be large, randomised trials, as there was strong evidence that increased daily intake of vitamin D could significantly improve the nation's health.

An earlier study revealed that teenage girls with higher vitamin D levels may have improved muscle performance. Not only does vitamin D work with calcium to keep bones strong, but researchers now found that teenage girls with higher vitamin D levels may be able to jump higher and faster than their peers with lower levels, according to a study published in the Journal of Clinical Endocrinology and Metabolism.

The UK researchers collected vitamin D levels for 99 girls, ages 12 to 14. To test the girls' muscle function, they were instructed to jump as high as possible while researchers used a device designed to measure power and performance called jumping mechanography. After allowing for differences in body weight, it was found that the girls with the highest vitamin D levels had the highest jump speeds, jump height, power and force.
 
The UK government already advises that pregnant and breastfeeding women should make sure they get enough vitamin D, taking supplements if necessary. And it is also recommended that children under five take daily vitamin D supplements.