There is something we can all do to strengthen our immune defences: drastically reducing our salt intake, which in the West, on average, is double the amount recommended by the World Health Organization. According to the WHO, in fact, we shouldn’t consume more than 5g per day, the equivalent of one level teaspoon, but data from the majority of Western countries has shown for years that on average we consume double this amount (for example, in Germany, men consume an average of 10 grams compared to 8 grams by women, and Italians 10.9 and 8.6 grams, respectively).
An excess of salt (sodium chloride) is a certain risk factor for strokes, heart attacks, and cardio- and and cerebrovascular diseases in general (something we have known for a long time). However, the quantity of salt we consume ought to be reduced, as we said, also because it tends to weaken our immune defences, as demonstrated by researchers from Bonn University (Germany) in a study published in the journal Science Translational Medicine. The German researchers carried out an initial series of tests on laboratory animals, putting them on a high-salt diet and then infecting them with Escherichia coli and Listeria bacteria. It was discovered that the spleens and livers of these animals accumulated bacteria concentrations ranging from 100 to 1000 times higher than animals considered normal, because their immune systems were not able to counter the replication of these bacteria. In addition, they took longer to heal from the infections caused by these two germs in the urinary tract and, more generally, in their entire bodies.
This data was then also confirmed in human volunteers. In particular, ten women and men, aged between 20 and 50, were given a daily dose of six grams of salt in addition to their normal daily intake for seven days (six grams is equivalent to the salt contained in two classic fast food meals, consisting of hamburgers and French fries). At the end of the week, the researchers took blood samples from the volunteers and put them in contact with a series of pathogens, with the aim of checking the response capacity of granulocytes, fundamental elements of the immune system. As expected, the granulocytes were much less efficient than those isolated from the same people prior to consuming the extra dose of salt. In addition to this, the number of glucocorticoids, like cortisol (a substance with a strong immuno-depressive ability), was higher than normal in the volunteers’ blood.
There are still several aspects to be cleared up about this weakening of the immune system, and it is to be noted that the German researchers did not carry out tests with viral agents. However, the data, in any case, provides another good reason for halving or greatly reducing our daily salt intake.
And one last thought: the work of the Bonn researchers “corrects” a series of other studies conducted in the past at international level which, on the other hand, had highlighted the anti-bacterial effect of salt in skin infections (the skin is the area of the body where excess salt is accumulated, awaiting to be digested). The German researchers in fact demonstrated that excess salt only has a positive effect on the skin, whereas the effects on the rest of the body are negative.