Salt is all over our plates, in bread, ham, cheese and almost all processed foods. We tend to exceed the recommended amount of sodium intake per day, which according to the World Health Organization, is 5 grams and we also know that eating too much salt is related to cardiovascular diseases. Now, scientists may have discovered the reason behind this relationship between salt and our hearts and it’s to do with our gut microbiota.

According to a new study published in Nature, a high salt diet alters the gut microbiota and these alterations may be associated with high blood pressure and autoimmune diseases such as multiple sclerosis in both mice and humans.

These results are significant and their confirmation may make gut microbiota a potential target for therapies to counteract diseases caused by a high salt intake.

The study was carried out by a group of researchers at the Berlin Experimental and Clinical Research Center and the Berlin Institute of Health (BIH). They wanted to know the exact mechanisms by which salt is a major risk for cardiovascular disease but, unlike any previous research, they focused on gut microbiota.

For the research, lab mice were fed a high-sodium diet containing 4% sodium chloride—salt—in comparison with the 0.5% present in a normal diet. The scientists discovered that the excess salt wiped out the levels of a particular kind of good bacteria called Lactobacillus. They then noted how this reduction had an impact on the numbers of a type of immune cell involved in autoimmune diseases and hypertension.

The good news is that when the researchers gave the mice a probiotic Lactobacillus called L. murinus, they got better, showing that the animals were able to overcome the effect of the high-salt diet. Although humans do not have L. murinus in their guts, the scientists believe another strain of Lactobacillus may play a similar role.

In fact, previous studies have already shown that Lactobacillus—found in several foods including yogurt and some types of cheese—lower blood pressure in people suffering from hypertension.

The scientists also ran a pilot study in humans with similar results. Twelve healthy men were given 6 extra grams of salt every day for two weeks while maintaining their regular diet, thus doubling their daily sodium intake. Scientists observed that 14 days later, most Lactobacillus species were no longer detectable.

Although the researchers were able to establish an association between salt and gut microbiota, they did not manage to completely elucidate the precise mechanism by which salt depletes most Lactobacillus species.

The question, therefore, is whether we will be able to treat salt-related diseases in the future using specific probiotic supplementation. The results are promising, but are only a first step and will need to be confirmed before any nutritional recommendations are made.

That is why the team of researchers is already planning a placebo-controlled high blood pressure study with a larger number of participants of both sexes. They also want to study the association between salt intake and gut microbiota with regard to psoriasis—an autoimmune skin disease—while also exploring the therapeutic applications of probiotics to treat these diseases.

While we already knew it was better to avoid a salty diet, this new study provides further reasons to restrict sodium intake. Less salt could mean better health—for you and your gut microbiota.

 

Journal reference:

Wilck N, Matus MG, Kearney SM et al.  Salt-responsive gut commensal modulates TH17 axis and diseaseNature, 2017. DOI: 10.1038/nature24628

Cristina Sáez
Cristina Sáez
Cristina Saez is a freelance science journalist. She works for several media, for instance the Spanish newspaper La Vanguardia, where she coordinates the science section, Big Vang; as well as research centres and scientific societies. She has been awarded for her journalistic work, among others, with the Boehringer Ingelheim Award in Medical Journalism 2015. Follow Cristina on Twitter @saez_cristina