It’s hardly news to hear that too much salt is bad for you, but new research has shown that a salt-rich diet can have an unexpected effect on your health beyond heart problems and high blood pressure.
A new study published in the journal Nature Neuroscience has found that mice fed a super salty diet show signs of declining mental performance and cognitive impairment due to their brains being starved of blood. After eating the high-salt diet, the mice had lost most of their hard-earned maze-solving skills. Eventually, they even stopped responding normally to a flick of their whisker.
This change in brain function occurred even if the high-salt diet didn't raise their blood pressure. This suggests that something else was going on, other than the well-established effects of salt on vascular health.
“The brain is a prime target of the harmful effects of salt,” the study reads. “We report that mice fed a high-salt diet develop marked cerebral hypoperfusion and a profound alteration in the endothelial regulation of the cerebral microcirculation, leading to subsequent cognitive impairment.”
To discover this, scientists fed a group of mice 8 to 16 times their normal salt intake, an amount the researchers say is “comparable to the high end of the spectrum of human salt consumption”. This marked a reduction of blood flow in both the cortex and hippocampus, two important brain regions that are associated with memory and learning.
"After about three months, the mice became demented," Dr Costantino Iadecola, director of the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine in New York, told ABC Australian News.
"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.”
This reaction was particularly strange because it was also seen in the absence of high blood pressure. Further investigation into this showed the high doses of salt were causing an immune response in the small intestine of the mice, resulting in an increased circulation of interleukin-17, an inflammatory substance that changes chemical firings within the brain's blood vessels.
While this study has only been carried out on mice so far, the researchers believe it's likely that the same applies to humans. Previous research has shown that salty diets are associated with loss of brain function, however, this was always thought to be closely tied to blood pressure problems. Now, this research has shown a clearer mechanism for how salt can afflict the brain directly.
In the meantime, try to limit your sodium intake to less than 2,300 milligrams per day – that’s equal to about one teaspoon of salt.