We all know that too much salt is bad for us and can cause heart problems and high blood pressure. However, new research has proven that a diet high in salt can cause other issues that you would never have expected.
Recently the journal Nature Neuroscience published a new study that says: “The brain is a prime target of the harmful effects of salt, and a high salt diet has been linked to cerebrovascular diseases and stroke, as well as cognitive impairment.”
During this study, the researchers fed mice a diet that had 8 – 16 times the amount of salt they would normally consume. This measurement is comparable to what humans who are on the high end of salt consumption take in on a normal basis.
The mice who were fed the high salt diet showed signs that their mental performance was declining when the effects on cognitive function were studied.
In the Barnes maze test, which requires spatial memory to learn and remember the location of an escape hole, they found that it took 3 days for the mice on both the normal diet and a high salt diet to learn where the escape hole was.
When they moved the escape hole to the opposite quadrant, the mice fed the high salt diet traveled much further and took longer to find the escape hole, which indicated a deficit in their spatial memory.
A test was performed to observe the reactions of the mice when their whiskers were stimulated. At 4 – 8 weeks, there was no change at all. However, by 12 weeks the mice had stopped responding normally.
They also tested the mice to see if a high salt diet affected their nesting behavior. Because burrowing and nest building is spontaneous rodent behaviors that depend on limbic function, it’s a good comparison to daily living activities which are often altered in human patients with cognitive impairment.
The researchers found the ability to build the nest and the amount of nesting material used, was reduced in the mice who were fed the high salt diet. This proved that there were profound changes in their cognitive function.
Even though the blood pressure did not raise in the mice on the high salt diets, their brain function diminished. This meant that something other than the effects of salt on their vascular health was to blame. The cognitive impairment occurred because the high salt diet reduced the resting cerebral blood flow and induced endothelial dysfunction.
Costantino Ladecola, who is director of the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine in New York said: “After about three months, the mice became demented. Mice are very curious and they like to look for new things, and so over time the mouse lost the ability to identify a normal object.”
Bryce Vissel is a Professor of Neuroscience at the University of Technology Sydney and Director of Neuroscience and Regenerative Medicine in the Faculty of Science. He explains how salt causes cognitive dysfunction: “It shows that it is doing it by causing profound immune changes in the gut resulting, in effect, in an almost autoimmune effect on the brain,” he said.
Basically, what you eat affects your gut in many ways.
“Those changes in the gut, in turn, cause all sorts of responses in the body, some of those are inflammatory and those responses over time certainly contribute to brain dysfunction,” he said.
“The extent to which it actually leads to things like dementia we don’t know, yet but the link between inflammation and brain dysfunction is very clear.”
So far, this study has not been tested on humans, but it is likely that we would have the same outcomes that the mice had. While previous research has shown that the loss of brain function can be associated with salty diets, it was thought to be connected to blood pressure issues. With this new research, we know that salt can affect the brain directly even when the blood pressure stays the same.
After the three-month study was finished, the researchers returned the mice to a normal mouse chow diet. After 4 weeks, they tested the mice and found that the effects of the salty diet were reversed by returning to a normal diet.
While health professionals recommend that we keep our salt intake equal to about one teaspoon of salt a day or less, many go over that amount. After all, a large order of fries at a fast-food restaurant probably has about that much salt in just one serving. After reading about this research are you planning to cut back on the amount of salt you consume?