Berlin: It’s a known fact that a high salt diet results in rise in blood pressure. But, too much salt intake also weakens the body’s immune system, a new study has found.
The finding, published in the journal of Science Translation Medicine, is unexpected as it contradicts the common notion that sodium chloride has a generally immune-enhancing effect.
"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," said Dr Christian Kurts of the Institute of Experimental Immunology at the University of Bonn, which conducted the study.
The researchers first fed mice with a high salt diet and the rodents were found to suffer from much more severe bacterial infections. Human volunteers, who were given an additional six grams of salt per day, too showed pronounced immune deficiencies.
As per the research, the body parts, except skin, are not exposed to the additional salt consumed and the same is filtered out by kidneys and excreted in the urine. The kidneys have a sodium chloride sensor that activates the salt excretion function. As an undesirable side effect, this sensor also causes so-called glucocorticoids to accumulate in the body. These, in turn, inhibit the function of granulocytes, the most common type of immune cell in the blood.
Granulocytes are the immune cells that mainly attack bacteria and, in their absence, bacterial infections proceed much more severely. The findings argue against high-salt consumption during bacterial infections. The skin, though, functions as a salt reservoir of the body and hence intake of additional sodium chloride works well for some skin diseases.
So, what’s the desirable salt quantity that can be consumed. It’s five grams a day or just under a teaspoon, according to the World Health Organisation (WHO).