The Connection Between a High-Salt Diet and MS
Salt has occupied both a pleasing sensation on the palate and a romantic place in our language. An “old salt” sails the briny seas. “Salt of the earth” describes a good, simple person. On the moral continuum of bad to good, salt in the ancient world was very, very good. It served as both flavor enhancer and food preservative. For centuries, salt was a popular trade commodity, harvested from salt mines and evaporated ocean water.
Different forms of sodium
Nowadays we take our salt in other ways, mostly in the form of sodium added to highly processed foods. That kind of sodium is different from table salt, otherwise known as sodium chloride. Sodium found in processed food such as monosodium glutamate (MSG), sodium ascorbate and sodium benzoate enhance flavor but also perform functions such as suppressing bitterness without adding a salty flavor and delaying spoilage.
While the body needs salt to function by maintaining hydration and facilitating chemical activity, too much can be toxic. Our fast, eat-on-the-fly culture makes it easy to ingest too much sodium. Medical research has long reported that levels higher than 2,500 mg per day can cause high blood pressure, kidney stones, and cardiovascular disease. Experts have more recently amended that to 1,500 mg or less of sodium as an even healthier goal. It is clear that less sodium is generally healthier for us. But how does sodium affect MS?
How does sodium affect MS?
Tests done on lab mice with EAE, the rodent form of MS, showed higher doses of sodium chloride produced more pro-inflammatory TH17 cells. It also increased the severity of disease symptoms in the mice. Inflammation is a consequence of TH17 immune cell attacks as they seek and destroy white and gray brain matter they perceive as enemy invaders. Interestingly however, giving the mice a high-salt and high-fat diet that resembled a human diet of fast food and probiotics resulted in a decrease of TH17 cells.
“It is really surprising to me how diet can really influence the degree of inflammation in these animals,” said David Hafler, MD, who chairs the Neurology Department at Yale School of Medicine. “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.” That was quoted in an April 2017 article before a human study was done.
Salt and inflammation
In October 2018 a new paper by Tomokazu Sumida, et.al, an associate research scientist working at the Hafler laboratory at Yale School of Medicine, was published in Nature Immunology where a study analyzing T cells taken from people with MS found an imbalance between a pro-inflammatory cytokine named IFN-gamma and an anti-inflammatory cytokine known as interleukin 10 (IL10). T cells, or Tregs, control the immune response by suppressing or regulating other immune cells. The researchers discovered that a protein called beta-catenin plays a major role in keeping Tregs functioning in that regulatory role. Moreover, the team explained this phenomenon as occurring in patients using a high-salt diet.
Sumida believes that further research should focus on preventing pro-inflammatory cytokines (IFN-gamma) and enhance anti-inflammatory cytokines (IL-10) with a goal of balancing the two. "Since this imbalance is enhanced in a high-salt environment,” he concludes, “the people at risk of developing MS should consider lowering their salt intake."
Future studies of the impact sodium has on our active disease will surely reveal the molecular mechanisms that lead to increased inflammation. If we take it with a grain of salt, we can think critically, use common sense about eating a lower sodium diet rich in vegetables and fruit, and keep our minds open as we ponder these most recent results of the connection between salt and multiple sclerosis.
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