The genetic component
Even if it turns out that sunlight/vitamin D level does determine the geography of MS, it is not the only environmental factor, Dr. Ebers notes. Smoking, virus infection and early-life hygiene all influence disease susceptibility within the context of genetic factors. “Indeed, we showed several ways in which vitamin D interacts with the genetics,” he explains. “The old argument about genes versus environment has been settled: It is both, and they interact.”
Other research found that both the main genes and a number of the small genes that predispose a person to MS are regulated by vitamin D. Dr. Ebers’ group discovered that people who have a genetic deficiency of an enzyme called 1,25-alpha-hydroxylase, which converts vitamin D to the active form, were more likely to develop MS.
Dr. Ebers previously practiced at the London (Ontario) Health Sciences Centre, where he conceived and initiated the Canadian Collaborative Project on Genetic Susceptibility to MS. This project comprises data and DNA on some 30,000 people with MS and their families.
For 25 years, starting in the early 1980s, Dr. Ebers also followed about a thousand people with MS in Canada. These people had received no treatment for 20 years or more, in most cases because disease-modifying treatments were not yet available. “It’s important to understand the disease course without treatment,” he notes, in order to compare the long-term effects of treatment, given the short-term nature of clinical trials. These studies of the “natural history” of MS have also led to important insights, such as understanding the average number of MS relapses a person may experience; the predictive value of the early course of MS; and the features of primary-progressive MS.
D is for determination
Dr. Ebers thinks it eventually may be possible to prevent MS by adding vitamin D to foods to increase people’s intake of the vitamin. “Unexpectedly, there are hints that vitamin D may help people who already have the disease, as small studies show some MS improvement in people with MS taking high doses of vitamin D,” he says, “but there is much more work needed to substantiate this.”
Some research suggests the possibility that vitamin D supplements taken during pregnancy and the early years may reduce the risk of a child developing MS later on. “In fact, if you do supplement with vitamin D, it may change the risk for your children or grandchildren,” he says, “and there is good evidence for effects from exposure in previous generations, which ramps up the stakes in any decision about supplementing on a large scale.” Similar efforts, such as folic acid supplementation to reduce certain severe birth defects, have been successful.
Dr. Ebers says he has been interested in MS ever since he was a neurology resident at Cornell University in the 1970s. Thirty-five years later, “I’m still at it,” he says. And although he hasn’t broken the case entirely, “We’ve covered a lot of ground,” he says. “There’s lots of progress!”
Elinor Nauen is a health writer based in New York City.