High salt diet hobbles the brain

A new study has shown that mice fed with a very high-salt diet experienced declined blood flow to their brain, the integrity of blood vessels in the brain suffered, and performance on tests of cognitive function plummeted.

Researchers found that those effects were not as long has been widely believed, a natural consequence of high blood pressure. Instead, they appeared to be the result of signals sent from the gut to the brain by the immune system.

The study, conducted by researchers at Weill Cornell Medicine in New York. The research sheds light on a subject of keen interest to scientists exploring the links between what we eat and how well we think, and the mediating role that the immune system plays in that communication.

This suggests that even before a chronic high-salt diet nudges blood pressure up and compromises the health of tiny blood vessels in the brain, the oversalted gut is independently sending messages that lay the groundwork for corrosion throughout the vital network.

In the small intestines of mice, the authors of the new research found that a very high-salt diet prompted an immune response that boosted circulating levels of an inflammatory substance called interleukin-17. These high levels of IL-17 set off a cascade of chemical responses inside the delicate inner linings of the brain's blood vessels.

The result in mice fed with the high-salt diet: blood supply to two regions crucial for learning and memory-the cortex and hippocampus slowed markedly. And mental performance slid. Compared to mice fed a diet lower in salt, the maze-running skills of the mice who consumed high-salt levels faltered, and they failed to respond normally to whisker stimulation, or a new object in their cage.

In mice, that evidence of cognitive impairment was apparent even in the absence of high blood pressure. The immune system's role in sending signals between brain and gut is also seen in diseases like multiple sclerosis, rheumatoid arthritis, psoriasis and inflammatory bowel disease-all disorders that are linked to poor functioning of the brain's blood vessels.
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