New research suggests that a diet high in salt may promote cognitive decline by destabilizing levels of the protein tau. Excessive levels of tau are a hallmark of dementia.

Share on Pinterest Avoiding excessive salt intake could stave off dementia.

Dr. Giuseppe Faraco, an assistant professor of research in neuroscience in the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine in New York, is the lead author of the new study, which appears in the journal Nature Neuroscience.

As Dr. Faraco and team explain in their paper, an excessive intake of salt has always had associations with poor cerebrovascular function, and high salt intake is an independent, well established risk factor for dementia.

But the more intriguing question is, how does excessive salt trigger dementia?

Previous research in rodents led by Dr. Faraco — together with Dr. Costantino Iadecola, director of the Feil Family Brain and Mind Research Institute and a co-author of the new study — started to elucidate this mechanism.

In the previous study, the researchers found that a diet high in sodium leads to dementia in mice by triggering the overproduction of a molecule that promotes inflammation.

The molecule, interleukin-17 (IL-17), stops brain cells from producing nitric oxide. Nitric oxide has the role of helping blood vessels to widen, which allows blood to flow. However, insufficient levels of nitric oxide can lead to restricted blood flow

In this mouse study, a high salt diet triggered high levels of IL-17, which in turn, lowered nitric oxide levels and reduced blood flow by 25%.

Building on this previous research, Dr. Faraco and team hypothesized in the new study that high levels of sodium would do the same thing — cause dementia by restricting the blood flow to the brain, an effect mediated by low nitric oxide.

However, the experiments revealed something unexpected.