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How does the increased consumption of salt affect the brain and memory?
Salt contains various essential minerals and trace elements, which are important for the human body. The problem is that too much salt is harmful. Researchers have now discovered that salt can even have a negative impact on our brain. A high-salt diet can lead to cognitive impairments and also to high blood pressure, vascular inflammation and cardiovascular diseases.
The scientists at Weill Cornell Medicine at Cornell University found that the effects of salt-rich diets were previously unknown. The salt leads to cognitive losses in the brain. The doctors published the results of their study in the journal "Nature Neuroscience".
How does too much salt affect the human body?
Eating too much salt can lead to various known negative effects on the human body. These include, for example, high blood pressure, vascular inflammation and cardiovascular diseases. A previous study has already shown that heart failure threatens if the salt consumption is too high. Puberty may even be delayed. However, it was previously unknown that too much salt also appears to have a direct impact on human cognitive performance.
Doctors use mice to study the effects of a high-salt diet
In their current study, the researchers investigated in mice whether a salt-rich diet affects blood flow to the brain and the cognitive performance of the animals. In the experiment, the mice were given special food which contained four to eight percent sodium chloride. This is comparable to a high-salt diet in humans, the experts explain.
The first changes were observed after only eight weeks
The result was clear. After just a short period of eight weeks, the diet caused significant changes in the animals' brains. The brain cortex of the mice was poorly supplied with blood by about 28 percent, the scientists say. This could be determined by a so-called magnetic resonance tomography (MRT). The hippocampus, which is important for memory, was also affected. The doctors found that blood flow in the hippocampus decreased by 25 percent.
The mental performance of the mice deteriorated due to the high consumption of salt
With the help of two memory tests, the scientists were also able to determine that the mental performance of the animals had deteriorated. The animals could no longer remember whether they had seen an object before or not. Every object was examined and examined intensively, as if the mice had never seen it before. This effect did not occur in the animals in the control group, the authors explain.
Cognitive deterioration affected old and young mice
Further deficits were also shown in a test in which the mice had to walk through a labyrinth. The animals with the salt-rich diet took significantly longer to find the exit despite a three-day learning phase. This can indicate a deficit in spatial memory, say the doctors. Such deterioration in cognitive performance has been observed in young and old mice.
What is the cause of the neurological effects observed?
Of course, the scientists tried to find out what caused these neurological failures. The doctors found no evidence of increased activity of inflammatory enzymes, explains author Giuseppe Faraco. Inflammatory changes in the brain vessels, which lead to reduced blood flow and thus influence the functions of the brain, could thus be excluded. However, the doctors found that the TH17 immune cells increased in the intestines of animals with a salt-rich diet. This then led to an increase in the release of the messenger substance interleukin-17 (IL-17). This messenger substance reaches the brain via the blood, where it affects the supply of nitrogen monoxide to the blood vessels, the doctors explain. Nitric oxide is important for good blood flow to the brain.
Eating too much salt damages the brain vessels
Such a connection between the intestine and the brain was previously unknown, say the scientists at Cornell University. The combination can cause excessive salt intake to damage the brain's vessels, resulting in poor brain function and cognitive performance. The blood pressure has no influence, the experts add.
How much salt should people consume per day?
The observed effect can probably also occur in humans. The mechanisms involved are also present in humans, this could be observed in the first cell culture experiments. Even if you don't have high blood pressure, you should still limit your salt intake. The experts from the World Health Organization (WHO) recommend that people should not consume more than six grams of salt a day.
The cognitive losses are reversible
However, the authors also explained that the cognitive losses found in the study by consuming too much salt can also be reversed. If the test animals resumed a normal diet with less salt over a period of a few weeks, the memory performance of the mice improved again. (as)