Salt affects the gut microbiome
High salt intake linked to hypertension and fatigue, but improvement seen with probiotics
High salt inake reduces the number of certain lactic acid bacteria in the gut of mice and humans according to a study published in Nature. This has an impact on immune cells which are partly responsible for autoimmune diseases and hypertension. Probiotics could help to reverse the harmful effects of excessive salt.
In late 2017, an article was published in Nature, a leading science journal, on a mouse study combined with a pilot study in humans focusing on the effect of salt on the gut microbiota. The study was conducted jointly by the Max-Delbrück Center for Molecular Medicine and Charité – Universitätsmedizin in Berlin. The scientists involved in this innovative research are among the first ever to look into the effect of a high salt intake on the gut microbiota and – by extension – on immune cells. Certain immune cells, which are affected by a high salt intake, play a role in the onset of some autoimmune diseases including myalgic encephalomyelitis (ME; also known as chronic fatigue syndrome (CFS)) and hypertension. The scientists suspected that excessive salt intake would have a negative effect. The research showed this to be the case.
To examine the effect of a diet high in salt on the microbiota, the researchers compared the droppings of two groups of mice. One group were fed a so-called High-Salt Diet (HSD) while the other group were fed on a Normal-Salt Diet (NSD). The microbiological analyses of their droppings showed that the mice in the HSD group had fewer lactobacilli – Lactobacillus murinus in particular – in their gut than the mice in the NSD group. The scientists also found more so-called T helper 17 (TH17) cells in the first group. TH17 cells are associated with hypertension and autoimmune diseases including ME. Then, ME was induced using an experimental model. At the same time, a strain of Lactobacillus murinus was administered to the mice. This resulted in a drop in TH17 cells. Blood pressure in this group of mice also dropped as a result of the reduction in TH17 cells. In other words, the negative effect of a high-salt diet on ME and hypertension in mice was reversed by administering Lactobacillus murinus.
The negative effect of a high-salt diet on ME and hypertension in mice was reversed by administering
Based on these findings, the same research group also initiated a pilot study with a small group of healthy men. During this so-called moderate high-salt challenge, their daily salt intake was increased by 6 grams for 2 weeks (resulting in an average salt intake of 13.8 ± 2.6 g per day). The conclusion? In people, too, hardly any lactobacilli could be found in the gut after the high salt intake. In addition, as in the mice, an increase in TH17 cells and elevated blood pressure were seen. Although Lactobacillus murinus does not occur in the human gut, the scientists believe that other Lactobacillus strains may have a similar protective effect in humans against the negative effect of excessive salt intake.
The researchers concluded that the gut microbiota plays an important part in diseases associated with a high salt intake. The reason is that our gut bacteria influence our immune system and the immune system is highly active in our gut. Although extensive follow-up research will be required, this research shows there may be a therapeutic role for microbiota management with probiotics (lactobacilli) in such conditions as ME and hypertension.
The gut microbiota plays an important part in diseases associated with a high salt intake.
1. Wilck N, Matus MG, Kearney SM, et al. Salt-responsive gut commensal modulates TH17 axis and disease. Nature 2017;551:585-9.
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