A diet rich in salt is linked to an increased risk of cerebrovascular diseases and dementia, according to new research published in the journal Nature Neuroscience.
Experiments carried out on human and mice cells suggest that salty foods trigger an inflammatory immune response that deprives the brain of oxygen, which damages neurons and leads to cognitive impairments.
The mice also struggled to identify new objects in recognition tests, which shows that their non-spatial memory had deteriorated. These effects were reversed when a normal amount of salt was consumed.
During the study, researchers fed mice a diet high in salt (roughly comparable to more than one teaspoonful a day in humans). The mice on a high salt diet struggled to navigate a maze that tested their ability to find an escape hole. They were also less capable of building a nest.
This could be partly explained by the gut’s immune response to salt. This includes an increase in the number of TH17 cells, They release a pro-inflammatory chemical called IL-17, which cause damage to endothelial cells and a reduction in blood flow to the brain.
This chemical reaction suppresses nitric oxide, which is essential in the process that allows the hippocampus to form new memories, and is important to cognitive function. In Alzheimer’s patients the flow of blood to the brain is believed to be reduced.
The effects of a salty diet were reversed in mice after four weeks. Brain scans showed blood flow and endothelial function were healthy again by this point. The head of research at Alzheimer’s Research UK says this demonstrates that a change in lifestyle – or new prescription drugs – could help reverse or prevent these effects.
‘This research not only highlights the importance of the immune system for brain health but also suggests that changes in the gut can play a role.’
‘The findings highlight the importance of cutting out excess salt in our diets, as well as identifying possible new avenues in the search for treatments to help those with memory problems or dementia.’