Research has found that a high-salt diet, besides being bad for your heart, may also harm your brain and lead to dementia.

In mice, the high-salt diet reduced the resting cerebral blood flow by 28 per cent in the cortex and 25 per cent in the hippocampus, both of which are brain regions involved in learning and memory. This impairement in the blood flow to the brain was caused by a decrease in the production of nitric oxide, a gas generated by endothelial cells. "We discovered that mice fed a high-salt diet developed dementia even when blood pressure did not rise," said Costantino Ladecola, Professor at Weill Cornell Medicine, New York. "This was surprising since, in humans, the deleterious effects of salt on cognition were attributed to hypertension," Ladecola added.

In the study, published in Nature Neuroscience, the mice were given food containing four per cent or eight per cent salt, representing a 8- to 16-fold increase, comparable to the high end of human salt consumption. Rodents that only ate the high-salt diet developed dementia, and performed significantly worse on object recognition tests, a maze test, and nest. Further, as a result of the high salt intake, the mice's white blood cells produced more interleukin 17 (IL-17), a protein known to regulate immune and inflammatory responses, and reduce nitric oxide in endothelial cells.

However, when the researchers treated the mice with a drug called ROCK inhibitor Y27632, it reduced the levels of IL-17 and reduced the production of nitric oxide. Professor Ladecola noted that the drug also improved behavioural and cognitive functions in mice. "The IL-17-ROCK pathway is an exciting target for future research in the causes of cognitive impairment. It appears to counteract the cerebrovascular and cognitive effects of a high-salt diet," explained Giuseppe Faraco, Assistant Professor at the varisty. The results illuminate a potential future target for countering harmful effects to the brain caused by excess salt consumption.