Scientists link high-salt diet to dementia for the first time

If you’re the kind of person who loves to include a lot of salt in your diet, a new study has suggested that it may actually increase your risk of dementia.

In fact, tests on mice have concluded that high-salt diets have reduced the resting blood flow to the brain, resulting in test mice to develop dementia. The findings of the study were recently published in Nature Neuroscience.

The research by Weill Cornell Medicine is said to be one of the first to link a diet to a neurovascular and cognitive impairment and raises questions of how high levels of salt could impact humans and their risk of dementia. The research discovered that mice developed dementia when consuming a high-salt diet, despite their blood pressure levels remaining low.

There are more than 100 different types of dementia, with Alzheimer’s Disease currently one of the most commonly diagnosed versions in the world. People typically show symptoms of the disease in their 50s, however, some people as young as 20 have been diagnosed with the disorder.

The current results have been described as “surprising” by senior author Dr Costantino Iadecola, director of the Feil Family Brain and Mind Research Institute and the Anne Parrish Titzell Professor of Neurology at Weill Cornell Medicine. “We discovered that mice fed a high-salt diet developed dementia even when blood pressure did not rise,” he said. “This was surprising since, in humans, the deleterious effects of salt on cognition were attributed to hypertension.”

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The average Australian consumes roughly 2,500mg of sodium daily, while the number in the US is slightly higher at 3,593mg. Experts recommend that 2,300mg is the recommended intake, meaning that if the study is proven in humans, people may unintentionally be contributing to a decline in their cognitive health.

For the research, the mice were given a diet with increased levels of salt that mirrored the increased levels of salt consumed by humans in their diets. After two months on the new diet, scientists discovered that resting cerebral blood flow in two areas of the brain that focus on memory and learning were reduced. They also found that cells lining blood vessels reduced nitric oxide that prompts blood flow by relaxing blood vessels.

The research team later changed the diets of the mice for a month and discovered that the memory function and blood flow returned to normal, signalling that reducing salt in a human diet may also have similar results. Their findings also suggested that mice that only consumed high-salt diets developed dementia and showed an inability to perform tasks that mice usually do including nest building. This is similar to many people living with dementia, who gradually lose their ability to perform the most basic of tasks. 

The researchers also performed other experiments and found that mice with high-salt diets developed immune responses in their guts and increased levels of white blood cells that could impact other immune cells. The higher levels of white blood cells actually boosted a protein called interleukin 17 which in turn, caused the nitric oxide to reduce. They ended up using a drug called ROCK inhibitor Y27632 that reduced levels of interleukin 17 and resulted in the mice returning to near-normal cognitive behaviours.

Testing hasn’t yet occurred on humans, but these early studies could provide vital information when it comes to curing and treating dementia.

Would you reduce your salt intake if you thought eating an excessively salty diet increased your chances of developing dementia?