A high-salt diet is not only bad for one’s blood pressure, but also for the immune system. This is the conclusion of a current study under the leadership of the University Hospital Bonn. Mice fed a high-salt diet were found to suffer from much more severe bacterial infections. Human volunteers who consumed an additional six grams of salt per day also showed pronounced immune deficiencies. This amount corresponds to the salt content of two fast food meals. The results are published in the journal Science Translational Medicine.
Five grams a day, no more: This is the maximum amount of salt that adults should consume according to the recommendations of the World Health Organization (WHO). It corresponds approximately to one level teaspoon. In reality, however, many Germans exceed this limit considerably: Figures from the Robert Koch Institute suggest that on average men consume ten, women more than eight grams a day.
This means that we reach for the saltshaker much more than is good for us. After all, sodium chloride, which is its chemical name, raises blood pressure and thereby increases the risk of heart attack or stroke. But not only that: “We have now been able to prove for the first time that excessive salt intake also significantly weakens an important arm of the immune system,” explains Prof. Dr. Christian Kurts from the Institute of Experimental Immunology at the University of Bonn.
This finding is unexpected, as some studies point in the opposite direction. For example, infections with certain skin parasites in laboratory animals heal significantly faster if these consume a high-salt diet: The macrophages, which are immune cells that attack, eat and digest parasites, are particularly active in the presence of salt. Several physicians concluded from this observation that sodium chloride has a generally immune-enhancing effect.
“Our results show that this generalization is not accurate,” emphasizes Katarzyna Jobin, lead author of the study, who has since transferred to the University of Würzburg. There are two reasons for this: Firstly, the body keeps the salt concentration in the blood and in the various organs largely constant. Otherwise important biological processes would be impaired. The only major exception is the skin: It functions as a salt reservoir of the body. This is why the additional intake of sodium chloride works so well for some skin diseases.