In a new study, researchers found a high-salt diet promotes cognitive impairment through the Alzheimer-linked protein tau.
A high-salt diet may negatively affect cognitive function by causing a deficiency of the compound nitric oxide, which is vital for maintaining vascular health in the brain.
When nitric oxide levels are too low, chemical changes to the protein tau occur in the brain, contributing to dementia.
The research was conducted by a team from Weill Cornell Medicine.
In the study, the team sought to understand the series of events that occur between salt consumption and poor cognition and concluded that lowering salt intake and maintaining healthy blood vessels in the brain may “stave off” dementia.
Accumulation of tau deposits has been implicated in the development of Alzheimer’s disease in humans.
The team found that a high-salt diet caused dementia in mice.
The rodents became unable to complete daily living tasks such as building their nests and had problems passing memory tests.
The research team determined that the high-salt diet was causing cells in the small intestine to release the molecule interleukin-17 (IL-17), which promotes inflammation as part of the body’s immune response.
IL-17 then entered the bloodstream and prevented the cells in the walls of blood vessels feeding the brain from producing nitric oxide. This compound works by relaxing and widening the blood vessels, allowing blood to flow. Conversely, a shortage of nitric oxide can restrict blood flow.
Based on these findings, the team theorized that salt likely caused dementia in mice because it contributed to restricted blood flow to the brain, essentially starving it.
However, as they continued their research, they realized that the restricted blood flow in mice was not severe enough to prevent the brain from functioning properly.
To further explore the importance of tau in dementia, the researchers gave mice with a high-salt diet and restricted blood flow to the brain an antibody to promote tau stability. Despite restricted blood flow, researchers observed normal cognition in these mice.
This demonstrated that’s what’s really causing the dementia was tau and not lack of blood flow. Overall, this study highlights how vascular health is important to the brain.
Although research on salt intake and cognition in humans is needed, the current study is a reminder for people to regulate salt consumption.
The team says the stuff that is bad for health doesn’t only come from a saltshaker, it also comes from processed food and restaurant food.
One author of the study is Dr. Giuseppe Faraco, an assistant professor of research in neuroscience.
The study is published in Nature.
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