BERLIN – Among a host of potential risk factors for multiple sclerosis (MS), one emerging risk factor – dietary sodium – has accumulating evidence, bolstered by new imaging techniques and emerging research about the mediating effect of the gut microbiome.
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“The word is still out on salt – there’s still some work to do; we are not where we stand with smoking or obesity” and the association with MS, said Ralf Linker, MD, speaking at the annual congress of the European Committee for Treatment and Research in Multiple Sclerosis.
For all potential emerging risk factors for MS, there’s an attractive hypothesis and, often, epidemiologic data, Dr. Linker said. “There are probably good [epidemiologic] data in multiple sclerosis for vitamin D, smoking, obesity, and probably also alcohol,” he said. “The therapeutic consequence, however, is much less clear, the best example of that being, of course, vitamin D.”
“The attractive risk factor is not enough to be a hypothesis, although some people seem to believe that nowadays,” said Dr. Linker, chair of the department of neurology at Friedrich-Alexander University, Erlangen, Germany. “Probably it’s better to start with some basic science and some experimental data to get an idea of the mechanism.”
“Today, we need clear associations with clear markers, well-defined cohorts, and proper epidemiological data telling us whether this is a real risk factor. ... If you look at the clinicians – and there are many among us in the room here – your ultimate goal, of course, is to use this as an intervention.”
For salt intake, there’s a clear overlap between high salt consumption in Westernized diets and increasing incidence of MS. The association also holds for many other autoimmune diseases, Dr. Linker added.
“The next step is experimental evidence,” Dr. Linker said. In a rodent model of experimental autoimmune encephalomyelitis (EAE), rats with high salt intake had a worse clinical course, compared with control rats fed a usual diet (Nature. 2013 Apr 25;496[7446]:518-22).
“There were a lot of follow-up studies on that,” with identification of multiple immune cells that are up- or down-regulated via distinct pathways in a high-salt environment, Dr. Linker said.