You have probably heard it a hundred times. Cut back on salt, your heart will thank you. Many of us now watch the shaker and squint at labels when shopping.
A new mouse study from Zhejiang University hints the brain may not do well on either extreme. Memory suffered on a very low-salt diet about as much as it did on a very high-salt one.
The paper appeared in the journal Food Research International in October 2026. It is one of the first to track the gut and the brain in the same animals eating too little salt and too much salt.
What the researchers actually did
The team used 32 male mice. They cleared out the animals' own gut bacteria with antibiotics, then transplanted human gut bacteria from healthy donors.
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The mice were split into three diets for 14 weeks. One group ate normal salt (0.5 percent of the diet). One got a very low-salt version (0.1 percent). The last ate a very high-salt version (8 percent).
The researchers tested working memory with a Y-maze. They tested longer-term memory by seeing whether mice could spot a new object next to a familiar one.
Only the normal-salt group kept their memory sharp. Both the low-salt and the high-salt groups made more errors on the memory tasks.
How low salt starved the brain's memory tools
Memory does not just happen. It is built from tiny proteins at the junctions between brain cells, called synapses, that help the cells pass signals along.
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In the low-salt mice, those proteins were in short supply. Three well-known memory proteins named SYN1, PSD95 and BDNF were reduced in the hippocampus, the part of the brain most linked to memory.
The researchers did not find higher inflammation in these animals. The brain simply seemed short on the gut-made chemicals it normally uses to keep its memory machinery running.
How high salt sent inflammation from the gut to the brain
The high-salt mice had a different problem. Their gut bacteria shifted toward more pro-inflammatory species, and inflammatory signals rose in the blood.
Beneficial short-chain fatty acids called propionate and butyrate also dropped. These are chemicals the gut bacteria make from fiber, and they help calm inflammation in the body.
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The result was oxidative stress in the gut, raised inflammatory signals and lower levels of the same memory proteins in the hippocampus.
What this means and does not mean for your salt shaker
A few caveats first. The study was in mice, not people, and only in male mice. Fourteen weeks on an 8 percent-salt diet is far more extreme than almost any human diet.
But the finding fits a broader shift in how researchers talk about sodium. The brain, like the rest of the body, may need salt to sit inside a specific range, not just below a ceiling.
For context, the World Health Organization recommends adults keep sodium under 2 grams a day, equal to about 5 grams of salt. The American Heart Association sets a US limit of under 2,300 milligrams a day, with 1,500 milligrams listed as an ideal target.
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Most Americans still take in well over 3,000 milligrams of sodium a day, far above the recommended daily limit for adults. The new study does not change those numbers. The authors note that human trials are needed before anyone recommends shifting the salt advice.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.