Science Sub-Journal: Shock! A high-salt diet actually reduces immunity!

April 4, 2020 / / - A high-salt diet is not only harmful to blood pressure, but also to the immune system.
is the conclusion of a new study led by the University Hospital of Bonn.
on a high-salt diet were found to have more serious bacterial infections.
who ate an increase of 6 grams of salt per day also showed significant immunodeficiency.
this amount is equivalent to the salt content of two servings of fast food.
study was published in the journal Science Translational Medicine.
, according to the World Health Organization (WHO), the daily salt intake should not exceed 5 grams: this is the maximum amount of salt that adults should consume.
is about the equivalent of a teaspoon.
, however, many Germans consume much more than this limit: data from the Robert Koch Institute show that men consume an average of 10 grams a day and women more than 8 grams.
picture source: This means we take salt bottles far more often than we do for our benefit.
, sodium chloride, which is its chemical name, raises the risk of high blood pressure, which increases the risk of a heart attack or stroke.
, explains Professor Christian Kurts of the Institute of Experimental Immunology at the University of Bonn: "We are now proving for the first time that too much salt intake can significantly impair the important function of the immune system.
" was unexpected because some studies point in the opposite direction.
For example, in experimental animals, some skin parasitic infections heal significantly faster if high-salt foods are consumed: macrophages are immune cells that attack, eat, and digest parasites and are particularly active when salt is present.
several doctors concluded from this observation that sodium chloride has a generally immune-enhancing effect.
s skin is a repository of salt," said Katarzyna Jobin, lead author of the study, who later moved to the University of Wurzburg.
for two reasons: First, the body maintains a basically constant concentration of salt in the blood and organs.
otherwise important biological processes will be compromised.
exception is the skin: it is the body's salt bank.
that's why extra sodium chloride is effective for some skin diseases.
, other parts of the body do not come into contact with the extra salt in the food.
instead, it is filtered by the kidneys and excreted with urine.
this is where the second mechanism works: the kidneys have a sodium chloride sensor that activates salt excretion.
, however, as a side effect, this sensor can also cause so-called glucoticoids to accumulate in the body.
these in turn inhibit the function of granulocytes, the most common immune cells in the blood.
like macrophages, granulocytes are scavenger cells.
, however, they do not attack parasites, but mainly bacteria.
if the granulocytes do not reach sufficient levels, the infection will be more serious.
"we can prove this in mice infected with Listeria, " Dr. Jobin explains.
"We've had some of these animals eat high-salt food before."
in the spleen and liver of these animals, we found that the number of pathogenic bacteria increased by 100 to 1,000 times.
", a bacteria found in contaminated food, can cause fever, vomiting and sepsis.
in laboratory mice on a high-salt diet, urinary tract infections healed much more slowly.
also appears to have a negative effect on the body's immune system.
Kurts, said: "We looked at volunteers who ate 6g of salt a day.
that's probably the amount of two fast food servings, two burgers and two fries.
week after the test, the scientists took blood from their subjects and examined the granulocytes.
immune cells responded much worse to bacteria after subjects began to eat a high-salt diet.
in human volunteers, excessive salt intake can also lead to elevated levels of glucoticoids.
is not surprising that this suppression of the immune system: the most famous corticosteroids have traditionally been used to suppress inflammation.
only through the study of the entire organism can we find complex control circuits from salt intake to immunodeficiency," Kurts said.
", our work also illustrates the limitations of pure cell culture experiments.
" () Reference: Too much salt weakens the immune systemK. Jobin el al., "A high-salt diet compromises antibacterial neutrophil responses through hormonal perturbation," Science Translational Medicine 25 Mar 2020: Vol. 12, Issue 536, eaay3850 DOI: 10.1126/scitranslmed.aay3850.