New Lab Studies Add Evidence That High Salt Diets Increase Inflammation and May Have Implications for MS
• The results from two recently published laboratory studies suggest that high levels of salt shift the balance of the immune system toward inflammation, and that salt alters the function of several types of immune cells pertinent to MS.
• These two studies, which were both published in the Journal of Clinical Investigation, were led by Dr. David Hafler (Yale University) and Dr. Dominik Müller (Max-Delbruck Center, Berlin, Germany).
• Dr. Hafler is funded by the National MS Society to study the impact of high salt on the immune system, and the Yale team is also conducting a pilot clinical trial to explore the impact of high- and low-salt diets on MS disease activity.
Background: Eating high levels of salt, which is part of the typical Western diet, has been linked to heart disease, chronic inflammation, and cancer. Recent lab reports have also suggested that dietary salt can speed the development of the immune attack in an MS-like disease in mice, and that the mouse disease responds differently to salt depending on the gender and genetic makeup of the mice. One small study in people found a possible link between dietary salt levels and relapses in people with MS, but this study suggested a link, which is not the same as establishing an actual cause. So far, laboratory findings related to the effects of salt have been stronger than the few studies that have been reported in people. Understanding whether high dietary salt is a risk factor for developing MS or for worsening disease activity is an active area of research.
The Studies: Two studies recently published in the Journal of Clinical Investigation suggest that high dietary salt affects two types of immune cells in a way that increases inflammation, a state that is generally considered harmful in MS. A study by National MS Society-supported researchers at Yale University and Harvard Medical School led by David Hafler, MD, investigated the effects of high salt on regulatory immune cells called “Tregs.” Tregs normally suppress immune responses by other immune cells, but in people with MS Tregs have been shown to be less able to perform this helpful function to turn off attacks. The team showed in mice and in cells in lab dishes that high salt blocks the ability of Tregs to suppress potentially harmful immune cells, and shifts Tregs toward activity that increases inflammation.
The other study, by an international team led by Dominik N. Müller at the Max-Delbruck Center in Berlin, Germany, investigated immune cells called “macrophages.” This study showed that high salt blocks the activation of a subset of macrophages, reducing their ability to suppress inflammatory cells and creating an imbalance in the immune system. In mouse models, high salt diets also delayed wound healing.
Comment: Taken together, these laboratory studies add new evidence that high levels of dietary salt may increase inflammation and autoimmunity, and decrease the ability of regulatory cells and processes to limit harmful immune cell activity. More studies are needed to determine the possible role of a high-salt diet in the risk of developing MS and whether reducing salt intake may be helpful for reducing disease activity in people with MS. Dr. Hafler is funded by the National MS Society to study the impact of high salt on the immune system, and the Yale team is also conducting a pilot clinical trial to explore the impact of high- and low-salt diets on MS disease activity.