Too much salt can lead to mental decline

too much salt can lead to cognitive impairment. Now, scientists may know why. It triggers an immune response that leads to the formation of a protein that prevents brain cells from functioning properly. The results were published recently in the journal Nature.
have long known that a high-salt diet increases the risk of stroke. Salt was initially thought to cause high blood pressure, which damages the brain. But recent studies have shown that even people with normal blood pressure can cause problems by consuming too much salt.
Iadecola and colleagues at the Weill Cornell School of Medicine in New York wanted to know why salt itself is bad for the brain. To do this, they fed the mice food containing 8 to 16 times the normal amount of salt, and then put them on cognitive tests.
two months after being fed, the mice were unable to identify the new objects present in front of them, and were much slower in maze tests than mice on a normal diet.
, the Iadecola team thought that excess salt would reach the brain and cause damage. However, an analysis of brain tissue suggests that there are other reasons. Researchers found a build-up of tau proteins in brain tissue in mice linked to Alzheimer's disease.
researchers believe they already know why tau proteins are beginning to accumulate. The study found that a high-salt diet also increased the number of Immune system T-cells in the gut. These cells produce small chemical messengers, which travel through blood vessels in the brain, reducing the production of nitric oxide.
levels of nitric oxide in the brain can lead to reduced blood flow and increase the activity of an enzyme in brain cells called CDK5. It is this enzyme that promotes the formation of tau proteins.
when Iadecola and colleagues restored nitric oxide production in mice, their cognitive abilities improved. Similarly, mice that could not produce tau protein, or those treated with tau antibodies, did not show cognitive impairment.
suggests a causal relationship between salt in the diet, vascular dysfunction in the brain, and the production of tau protein in the brain.
also challenge the idea that low blood flow can cause dementia, because it shows that even if blood flow is still low, offsetting tau can reverse dementia, said Iedecola, a researcher at the University of New China. (Source: Zong Hua, China Science Journal)
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