Too much dietary salt decreases the blood flow in the brain and thus degrades short-term memory. This, according to a new study on mice.
It has long been known that too much salt can cause high blood pressure and thus increase the risk of cardiovascular diseases such as stroke and dementia.
It has also been known that salt adversely affects the brain, but how it does this and what it could imply has been unclear.
The research study had mice receive a very salty diet for five weeks, and they were then continually examined. The researchers discovered that the mice had poorer short-term memory. They did not find as well in mazes as the control group of mice did.
By studying the blood vessels of the mice, the researchers were able to see that there was an immune response triggered by the salt when it got into the stomach, which made it more difficult for the blood vessels to widen, which in turn led to a poorer blood supply.
The salt, therefore, does not directly affect the brain butis absorbed through the bowel digestion. The mice that had poorer blood flow and worse short-term memory got a diet that consisted of four to eight percent salt. About the amount we humans get when eating really salty foods.
The WHO recommends people to eat less salt; they contend that most people consume too much salt, on average 9–12 grams per day, or around twice the recommended maximum level of intake. Salt intake of fewer than 5 grams per day for adults helps to reduce blood pressure and risk of cardiovascular disease, stroke, and coronary heart attack, according to the WHO.
Although the new study was conducted on mice, it wouldn’t be surprising if the results could be translated to humans. The researchers argue that too much salt does affect our human brain negatively, as well.
Reference:
Costantino L et. al. “Dietary salt promotes neurovascular and cognitive dysfunction through a gut-initiated TH17 response“, Nature Neuroscience 2018, DOI: 10.1038 / s41593-017-0059-z