Salt harms the immune system
Five grams per day, no more, is the maximum amount of salt that healthy adults should consume in accordance with the recommendations of the World Health Organization (WHO). In reality, however, many significantly exceed this limit: according to the Robert Koch Institute, on average in Germany men consume ten, and women – more than eight grams of salt per day.
Meanwhile, sodium chloride increases blood pressure and increases the risk of heart attack or stroke. But the harm of excess salt does not end there. In a new study, scientists from the University Hospital Bonn have proven that excessive salt intake also significantly weakens an important element of the immune system.
The results contradict the data obtained by other scientists, who have shown, for example, that wounds infected with certain skin parasites heal much faster in laboratory animals that consume food with a high salt content. Macrophages are especially active in the presence of salt. From this observation, some immunologists have concluded that sodium chloride has an overall immunostimulating effect.
The skin serves as a salt reservoir
The results of the new study show that this generalization is not accurate. There are two reasons for this: firstly, the body must maintain a constant concentration of salt in the blood and in the organs. Otherwise, important biological processes will be disrupted. The only exception is the skin: it functions as a salt reservoir of the body. That's why supplemental sodium chloride intake works so well for some skin conditions.
However, other parts of the body are not exposed to the excess salt consumed with food. It is filtered by the kidneys and excreted in the urine. And here the second mechanism comes into effect: in the kidneys, excess sodium chloride is excreted not through an osmotic gradient, but with the help of urea. However, as an undesirable side effect, urea also causes the accumulation of glucocorticoids in the body. And they, in turn, suppress the function of granulocytes – the most common type of immune cells in the blood.
Granulocytes attack mainly bacteria. If granulocytes are not active enough, infections are much more severe. The researchers were able to demonstrate this in mice infected with listeria – bacteria that cause fever, vomiting and sepsis. Before that, some of the mice were fed food with a high salt content. In the spleen and liver of these animals, scientists have counted from 100 to 1000 times more pathogens. Urinary tract infections were also cured much more slowly in laboratory mice fed with a high salt content.
Sodium chloride also has a negative effect on the human immune system. The group surveyed volunteers who consumed six grams of salt in addition to their daily diet. About the same amount of salt is contained in two fast food dishes, that is, in two hamburgers and two portions of French fries. A week later, the scientists assessed the number and condition of granulocytes in the volunteers' blood. Immune cells fared much worse against bacteria after the subjects started following a diet with a high salt content.
In humans, excessive salt intake also led to increased levels of glucocorticoids, which also suppress the immune system.
Article by K.Jobin et al. A high-salt diet compromises antibacterial neutrophil responses through hormonal perturbation is published in the journal Science Translational Medicine.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of the Universität Bonn: Too much salt weakens the immune system.