We eat salt every day, sometimes more and sometimes less, but often too much. However, the impact of salt on intestinal bacteria has not been studied up to now. A research team headed by Prof. Dr. Ralf Linker of the Chair of Neurology at FAU recently discovered that table salt reduces the number of lactobacilli in the intestinal tract. This has an impact on immune cells that play a role in autoimmune disorders such as multiple sclerosis. Probiotics, on the other hand, can help alleviate the symptoms of such diseases. The researchers recently published the results of their work in the leading journal Nature (DOI: 10.1038/nature24628).
Lactobacilli offset the harmful effects of salt
A diet containing too much salt can lead to hypertension and even exacerbate the autoimmune disorder multiple sclerosis. Working with researchers from the Max Delbruck Center for Molecular Medicine in Berlin and the Massachusetts Institute of Technology, the researchers in Erlangen have demonstrated that too much salt decimates the number of intestinal lactobacilli. This goes hand in hand with an increase in the number of Th17 helper cells associated with autoimmune conditions.
However, when probiotic lactobacilli in addition to salty food were administered in animal models of multiple sclerosis, the number of pro-inflammatory Th17 helper cells decreased while there was alleviation of neurological symptoms. The researchers thus conclude that the profile of the microbiome – something that can be influenced by salt intake – is an important factor when it comes to the development of disorders like multiple sclerosis. This is because they have been able to demonstrate how, for example, intestinal bacteria can influence the immune system and thus affect the host organism.
Pilot trial with volunteers
In addition to using an experimental model, the researchers also investigated the bacterial microbiota in the intestinal tract of 12 healthy male volunteers who were given 6 additional grams of table salt daily for 14 days. This approximately doubled their daily intake of salt as the volunteers otherwise maintained their normal eating habits. The intestinal lactobacillus colony again reacted sensitively to this. In fact, in many intestinal areas, lactobacillus bacteria were no longer detectable after 14 days of increased salt consumption. At the same time, the researchers registered an increase in the number of pro-inflammatory Th17 helper cells in blood.
Ground-breaking findings for treatment
Research is now beginning to focus on the role played by bacteria in the pathogenesis of various diseases. But how the body interacts with its intestinal flora is still largely unknown. ‘Our work goes beyond simply looking at the changes caused by salt. Our real interest was in the interrelated processes,’ says Stefanie Haase, who supervises the project in the research laboratory of the Department of Neurology. But, as yet, she admits, they have not fully understood the various interactions. ‘We cannot rule out the existence of other salt-sensitive bacteria of similar importance.’
The results do not provide confirmation of the claimed therapeutic effects of the lactobacilli present first and foremost in fermented food such as sauerkraut, yoghurt and cheese. Prof. Dr. Linker adds: ‘Multiple sclerosis is among the salt-sensitive diseases we may subsequently be able to treat with personalised probiotics.’ This would mean that lactobacillus probiotics could well have a therapeutic potential. The effect of probiotics is to be further investigated with a view to developing, at some point in the future, possible treatments for multiple sclerosis.