Three studies published in the March 6 journal Nature suggest that high-salt diets may contribute to the development of autoimmune diseases, including multiple sclerosis (MS), rheumatoid arthritis, psoriasis, and arthritis of the spine.
“The diet does affect the autoimmune system in ways that have not been previously recognized,” senior study author David Hafler, MD, a professor of neurology and immunobiology at the Yale School of Medicine, in New Haven, Conn., told HealthDay News.
The study, which looked at the effect of salt on inflammatory producing cells, resulted from an accidental discovery when Hafler and his team noticed that people who ate at fast food restaurants more than once a week had high levels of inflammatory cells. Inflammatory cells are normally used by the immune system to fight infection. In autoimmune diseases, they attack healthy tissue.
Study researchers found that giving mice a diet high in salt increased the production of T-cells, infection-fighting cells associated with autoimmune diseases. Mice that were genetically engineered to develop MS had a severe form of the disease when fed high-salt diets.
In addition to Hafler’s study, which shows how salt may overstimulate the immune system, scientists from the Broad Institute in Boston looked into how genes regulate the immune response, and researchers from Harvard Medical School and Brigham and Women’s Hospital in Boston investigated how autoimmunity is controlled by a network of genes.
HealthDay reports that the different approaches of the three studies help explain how helper T-cells can drive autoimmune disease by creating inflammation. Salt appears to cause enzymes to stimulate the creation of T-cells, which increases the body’s immune response.
However, researchers caution that salt is not a sole contributing factor to autoimmune diseases.
“We don’t think salt is the whole story. It’s a new, unexplored part of it, but there are hundreds of genetic variants involved in autoimmune disease and environmental factors, too,” said Hafler.
In a Reuters interview, Hafler indicated that the findings needed to be studied in people. He now has permission to test the effects of lowering salt intake in the diets of MS patients to see if their symptoms improve.
Hafler acknowledges that it will be years before the link between salt and autoimmune diseases is confirmed. He does, however, think that for people already at risk of autoimmune disease, reducing dietary salt may be a good idea.
“If I had MS, I would think very much about not eating processed foods and really cutting down my salt intake,” said Hafler.