ORLANDO—A high-salt diet might be a key environmental risk factor for multiple sclerosis (MS), according to an overview presented at the ACTRIMS 2017 Forum. Since most research has been performed in vitro and in animal models, it remains unclear how a high-salt diet affects patients with MS. Researchers have found in experimental models, however, that salt induces inflammation by several mechanisms: it increases frequency of inflammatory TH17 cells, decreases function of suppressor cells, and increases inflammation of antigen-presenting cells.
“There’s been an epidemic of human autoimmune disease over the past 70 years,” said Dr. Hafler. Researchers are working to discover why there has been such a significant rise in cases. “Genetics cannot allow this to happen. There must be something in the environment,” said Dr. Hafler. He and his colleagues sought to understand how a high-salt diet affects MS.
“What we found is if you added sodium chloride to cultures of T cells, you have autoimmune increases in the frequency of TH17 cells,” he said. In addition, salt decreases function of suppressor cells, the Tregs, and increases inflammation of antigen-presenting cells of the immune system, said Dr. Hafler.
Previous research found that mice fed a high-salt diet were more prone to severe experimental autoimmune encephalomyelitis. When the mice were given a high-salt, high-fat diet that mimicked fast food and probiotics, researchers observed a decrease in inflammation.
“It is really surprising to me how diet can really influence the degree of inflammation in these animals,” said Dr. Hafler. “We do not know if this will work in humans, but probiotics may decrease inflammation. We have no information [on] whether a diet with a probiotic would help prevent or treat MS.”
According to Farez et al, a higher sodium intake is associated with increased clinical and radiological disease activity in patients with MS. Other studies have found that environmental factors such as smoking and low vitamin D levels are associated with MS risk, and the risk is genetically mediated. What may be an environmental risk for one individual may not be a risk for another individual, said Dr. Hafler. “It is unlikely that any of these factors by themselves—smoking, vitamin D, fat, and salt—would be critically important, but together, they might have a strong effect,” he said.
Since there is limited research on a high-salt diet in humans, Dr. Hafler does not recommend his patients with MS go on a strict low-salt diet. However, he does advise patients to stay away from processed foods and fast food. He also encourages patients to get most of their calories from fruits and vegetables.
“We are now doing studies in which we put patients and control subjects on a high-salt diet and low[-salt] diet to observe the direct effect in those individuals,” said Dr. Hafler.
—Erica Tricarico
Suggested Reading
Farez MF, Fiol MP, Gaitán MI, et al. Sodium intake is associated with increased disease activity in multiple sclerosis. J Neurol Neurosurg Psychiatry. 2015;86(1):26-31.
Jörg S, Kissel J, Manzel A, et al. High salt drives Th17 responses in experimental autoimmune encephalomyelitis without impacting myeloid dendritic cells. Exp Neurol. 2016;279:212-222.
Kleinewietfeld M, Manzel A, Tize J, et al. Sodium chloride drives autoimmune disease by the induction of pathogenic TH17 cells. Nature. 2013;496(7446):518-522.
Paling D, Solanky BS, Riemer F, et al. Sodium accumulation is associated with disability and a progressive course in multiple sclerosis. Brain. 2013;136(Pt 7):2305-2317.