A little salt to your dish? Great.
Too much salt in your diet? Terrible.
You may have long known that a high-salt diet leads to high blood pressure and raises the risk for stroke, which can damage your brain. The latest study, however, suggests that too much salt can cause cognitive impairment through a new mechanism.
In a previous study in 2018, scientists found that a high-salt diet caused dementia in mice. On the basis of this finding, the researchers from Weill Cornell Medicine conducted new experiments on mice to find out the reason behind it.
Why salt can be harmful to the brain
The researchers first fed mice a diet containing 8 to 16 times the normal amount of salt, then had those mice perform cognitive tests. It turns out that after two months on the high-salt diet, the mice were unable to recognize new objects and lost the ability to perform simple tasks.
At first, the researchers thought such damage to the brain was caused by high blood pressure due to restricted blood flow to the brain. But the restricted blood flow was not severe enough to damage the brain. Soon, they found something wrong in the brain tissue. Tau — a protein linked to dementia — accumulated in the brain tissue.
The build-up of tau
The researchers found that high salt intake reduced the production of nitric oxide (NO). Lower levels of NO led to low blood flow and activation of an enzyme (CDK5) in brain cells. The enzyme then led to the build-up of tau proteins, causing cognitive impairment in mice.
When the researchers treated the mice with anti-tau antibodies, they observed normal cognition in these mice along with restricted blood flow to the brain.
These findings show that eating too much salt causes the build-up of tau that stops brain cells from working properly. More importantly, even if the blood flow is still low in the brain, the researchers may counteract tau and thus reverse cognitive impairment.
What you should do
A high-salt diet can affect your brain healthy in more than one way. You should really limit your salt intake. The American Heart Association recommends 1,500 mg (1.5 grams) to 2,300 mg (2.3 grams) of salt per day.
What’s more, you should be careful with those processed food and restaurant food, as you won’t know the exact amount of salt they contain. Try to cook yourself!