New data suggest that high salt consumption may prove fatal to certain gut bacteria, and that this could contribute to high blood pressure and diseases affecting the immune system.

Scientists are already aware of a link between high blood pressure and a diet high in salt.

High-salt diets may also speed up the progression of autoimmune diseases, such as multiple sclerosis (MS).

A new study proposes a mechanism that may be behind this association.

The research was led by scientists from the Experimental and Clinical Research Center and Max Delbrück Center for Molecular Medicine in Berlin, Germany.

What is Lactobacillus?

A type of gut bacteria called Lactobacillus, found in some fermented foods—such as sauerkraut, yogurt, and cheese—are considered "good" bacteria; they are thought to offer protection against certain diseases.

Last year, for example, studies found that Lactobacillus inhibits the growth of several multidrug-resistant bacterial pathogens and may also help to reduce kidney inflammation in women with lupus.

The latest study, presented at the British Cardiovascular Society Conference in Manchester in the United Kingdom, suggests that eating a lot of salt could kill Lactobacillus and, thereby, increase the risk of disease.

High-salt diet killed off Lactobacillus

The researchers found that a version of Lactobacillus found in mice is destroyed when they are fed a diet high in salt. The high-salt diet also caused the mice's blood pressure to rise and triggered the activation of inflammation-inducing immune cells, called TH17 cells.

The mice also demonstrated symptoms of a neurological condition similar to MS called encephalomyelitis.

The authors found that encephalomyelitis symptoms and TH17 cell count could be reduced by giving the mice a probiotic treatment of Lactobacillus, which also stabilized the mice's blood pressure.

The authors then attempted to replicate their findings in humans. They recruited 12 healthy men who consumed 6 extra grams of salt each day for 2 weeks, effectively doubling their salt intake.

By the end of the 2 weeks, the authors found that, in most of the participants, Lactobacillus had been eliminated from their microbiomes—the ecosystem of organisms that live in our digestive system. Like the mice, the men in the study also had higher blood pressure and increased TH17 cell count.

More studies are needed

Although scientists already know that TH17 cells are affected by the gut microbiome, the finding that salt kills off healthy bacteria in the microbiome is new.

More and more, scientists are investigating the role that bacteria play in diseases, but there are a lot of unknowns when it comes to how the body interacts with the bacteria that reside in the gut.

The authors behind the study argue that more research is needed to better understand how gut health affects the health of the body's other systems, such as cardiovascular health, and the extent to which probiotics might provide useful treatments for conditions such as high blood pressure.

"We should start to see our gut microbiome as a viable target for treating conditions that we know are aggravated by salt, such as high blood pressure and inflammation."

–Study lead Professor Dominik N. Müller

"We can't exclude the possibility that there are other salt-sensitive bacteria that are just as important as Lactobacillus," he continues. "This could be the tip of the iceberg in targeting gut bacteria for treating serious illnesses."