In autoimmune conditions, the body undergoes an inappropriate immune response that causes excessive inflammation with destructive effects on cells and tissues. Currently, about 23.5 million Americans suffer from an autoimmune disease, and that number is rising.1 The reasons behind the increasing prevalence are unknown, but environmental influences, such as diet, are believed to play a role. I have reported here before that elevated blood pressure is not the only danger associated with salt. In my medical practice, I have observed beneficial effects of a low-salt diet for autoimmune conditions, and for years I have been advising patients with autoimmune disease to avoid added salt. Now, new research confirms my clinical observations that salt may increase the inflammation associated with several autoimmune conditions.
What are T helper 17 (TH17) cells?
TH17 cells are immune cells that are involved in the body’s defense against bacterial and fungal pathogens, and help to recruit other important immune cells to sites of infection. TH17 cells seem to come in two different varieties, the standard protective TH17 cell, and the pathogenic TH17 cell, depending on the particular molecules that drive their differentiation from immature T cells to mature T helper cells. Pathogenic TH17 cells produce more pro-inflammatory markers and appear to be involved in the abnormal immune responses associated with rheumatoid arthritis, psoriasis, inflammatory bowel disease and multiple sclerosis.2,3
Recent studies connect salt intake and pathogenic TH17 cells
Two recent studies published last week in Nature collectively suggest that excess sodium drives autoimmunity at the cellular level.4-6 One group of researchers had previously observed increased TH17 cell numbers in the blood of people who consumed fast food more often; hypothesizing salt might be involved, they conducted experiments on the effects of elevated sodium concentrations on the differentiation of immature human T cells into pathogenic TH17 cells. They indeed found that high sodium concentrations drove a dramatic increase (almost ten-fold) in differentiation into pathogenic TH17 cells in culture. To strengthen these findings, they fed mice predisposed to a TH17-related autoimmune disease either a standard or high-salt diet. The high-salt diet accelerated the development of the autoimmune disease, and the symptoms were more severe on the high-salt diet than on the standard diet.4,7
A separate group of scientists was investigating the changes in gene expression that occur during the differentiation process of immature T cells into pathogenic TH17 cells. They noticed increases over time in the expression of a protein called SGK1, which is known to mediate sodium transport and sodium balance in other cell types. They performed additional experiments, and they found that increased salt concentration increased SGK1 expression and, similar to the first study, pathogenic TH17 differentiation. These studies suggest that high salt intake may increase the numbers of circulating pathogenic TH17 cells, contributing to autoimmune inflammation.8
This research raises the possibility that increased salt intake may be a significant environmental influence driving the growing prevalence of autoimmune conditions.
We already know that excess salt intake is associated with elevated blood pressure, heart disease, stroke, kidney disease, osteoporosis, ulcers and gastric cancer;9 now autoimmune inflammation is another danger we can add to the list. For optimal health, we should minimize added salt and strive to consume only the sodium present in natural foods.
1. American Autoimmune Related Disease Association: Autoimmune Statistics [http://www.aarda.org/autoimmune_statistics.php]
2. Peters A, Lee Y, Kuchroo VK: The many faces of Th17 cells. Curr Opin Immunol 2011, 23:702-706.
3. Awasthi A, Kuchroo VK: Th17 cells: from precursors to players in inflammation and infection. Int Immunol 2009, 21:489-498.
4. Harmon K: Salt linked to autoimmune diseases. In Nature News; 2013.
5. Leslie M: Salty Food May Be a Culprit in Autoimmune Disease. In Science NOW; 2013.
6. Yandell K: Salt at Fault? In The Scientist; 2013.
7. Kleinewietfeld M, Manzel A, Titze J, et al: Sodium chloride drives autoimmune disease by the induction of pathogenic T17 cells. Nature 2013.
8. Wu C, Yosef N, Thalhamer T, et al: Induction of pathogenic T17 cells by inducible salt-sensing kinase SGK1. Nature 2013.
9. Tsugane S, Sasazuki S: Diet and the risk of gastric cancer: review of epidemiological evidence. Gastric Cancer 2007, 10:75-83.