Too much salt can lead to mental decline

Eating 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 stops brain cells from working properly The results were published in nature recently Scientists have long known that a high salt diet increases the risk of stroke Salt was originally thought to cause high blood pressure, which can damage the brain But recent studies have shown that even people with normal blood pressure can cause problems if they eat too much salt Costantino iadecola and colleagues at Cornell Medical College in New York want to know why salt itself is harmful to the brain To do this, they fed mice food containing 8 to 16 times the normal amount of salt and then tested them on cognition After two months of feeding, the mice were unable to recognize the new objects presented in front of them, and were much slower in the maze test than rats on a normal diet At first, the iadecola team thought that excess salt would reach the brain and cause damage However, the analysis of brain tissue shows that there are other reasons The researchers found an accumulation of tau protein in the brain tissue of mice, which is associated with Alzheimer's disease The researchers believe they already know why tau protein began 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 the blood vessels of the brain, reducing the production of nitric oxide A decrease in nitric oxide levels in the brain results in a decrease in blood flow and an increase in the activity of an enzyme called Cdk5 in brain cells It is this enzyme that promotes the formation of tau protein When iadecola and colleagues restored nitric oxide production in mice, their cognitive abilities improved Similarly, mice that did not produce tau protein, or were treated with tau antibodies, did not show cognitive impairment This shows that there is a causal relationship between salt in diet, vascular dysfunction in brain and the production of tau protein in brain The latest study also challenges the idea that low blood flow can cause dementia, says iadecola, because it shows that offsetting tau can reverse dementia even if blood flow is still low.