Researchers find correlation between salty diet and dementia

A new research finding has been revealed that salty foods can lead to a dramatic fall in blood flow in the cerebrum and impede the activity of brain cells, posing a possibility of causing cerebrovascular disorders and dementia.

On Monday, a research group led by Dr. Costantino Iadecola, director of the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine in New York, published a study on Nature Neuroscience about a specific process where a sustained intake of large portions of salt leads to declining functions of the brains.

The researchers provided low-salt (0.5 percent salt water and food) and high-salt food, which was 8 to 16 times salter than the bland diets, to a group of fully grown eight-week mice for as short as four weeks to as long as 24 weeks. MRI scanning was conducted to compare the levels of blood flow in the cerebrum and the number of blood cells.

The density of the high-salt diet from the study was referenced from the research data on the amount of salt intakes in 187 countries, which was published on the British Medical Journal by a group of researchers from the University of Cambridge in 2013. “The amount of salt in the high-salt diet is equivalent to 22 grams a day for humans, and this is even higher than the region that consumes the largest amount of sodium,” said Dr. Iadecola in an email interview with The Dong-A Daily. In the 2013 study, Central Asia was found to be the largest consumer of salt (14 grams a day per person), followed by Japan and South Korea (12.7 grams a day per person). “Considering that the surveyed data tends to be rather conservative, the density of sodium employed in our study is more realistic,” said Dr. Iadecola.

His research team has found that high-salt diet cut blood flows by 25 percent to 28 percent in cerebral cortex, which governs thought, and in the hippocampus, which governs memory. By contrast, the number of leukocytes in the intestines went up dramatically. A surge in the number of white blood cells called TH17 led to generation of inflammatory cytokines called IL-17, which travelled into the brains through blood vessels, having a detrimental effect on brain functions. The Cornell researchers conducted an experiment of putting mice in a maze to find the way out, and the mice from the high-salt diet group took more time to reach the exit, owing to deteriorated space memory.

“The good news is that once they cut back on the amount of sodium intake, the mice came back to a normal state,” said Dr. Iadecola, warning against the global trend of increasing sodium intake.

ashilla@donga.com