Too Little Salt Can Hurt Memory Just Like Too Much, Study Finds

If you have been told to slash your sodium for your blood pressure, or you have never met a salty snack you could resist, a new mouse study adds an unexpected wrinkle to that picture. Researchers found that both extremely low and extremely high salt intake disrupted the gut microbiome and impaired memory, suggesting the gut-brain axis (the communication network linking gut bacteria to brain function) has a sweet spot for sodium, not just a ceiling. For anyone managing blood pressure, kidney issues, or a gut condition where diet already feels like a minefield, the finding is a reminder that "less is better" does not always hold.

Key takeaways:

• Mice on both an extremely low-salt diet and an extremely high-salt diet performed worse on memory tests than mice on a normal-salt diet, in a 14-week study using mice carrying transplanted human gut bacteria.
• The two diets appear to harm memory through different routes: high salt through gut inflammation, low salt through reduced short-chain fatty acids (gut bacteria byproducts), without inflammation.
• Both diets lowered hippocampal synaptic proteins (SYN1, PSD95, BDNF) tied to memory formation.
• Caveat: this is a mouse study with salt levels far more extreme than typical human diets, and the full paper was not available for this article; this summary relies on the study's published abstract and reporting on its findings.

Both Low-Salt and High-Salt Diets Impaired Memory in Mice

Mice fed either a severely low-salt or an extremely high-salt diet for months developed measurable memory problems compared to mice on a normal-salt diet, according to a study published in Food Research International (DOI: 10.1016/j.foodres.2026.119719) by Anji Chen and colleagues. Mice on both extreme diets "struggled with memory," performing worse on tests of short-term working memory and long-term recognition memory than mice eating a normal amount of salt. In the hippocampus (the brain region central to forming new memories), both diets lowered levels of three synaptic proteins, SYN1, PSD95, and BDNF, and suppressed activation of CREB, a protein that helps neurons strengthen the connections memory relies on.

Why Gut Bacteria, Not Just Sodium, May Be the Real Driver

The twist is that the two diets appear to damage memory through different routes that both run through the gut microbiome. Both diets altered the composition of gut bacteria and reduced levels of propionate and butyrate, short-chain fatty acids (byproducts of bacterial fermentation that help maintain the gut lining and are increasingly tied to brain health, as a review of gut-brain communication describes). But the high-salt diet additionally triggered inflammation: it was associated with increased pro-inflammatory gut bacteria, elevated circulating inflammatory cytokines, and broad changes in lipid metabolism. The low-salt diet produced none of that systemic inflammation; instead, it further suppressed microbial output of acetate and isobutyrate, suggesting it starves the gut of metabolic byproducts the brain needs rather than inflaming it. That distinction matters for anyone with an inflammatory gut condition such as IBD, since it suggests high salt and low salt are not simply opposite doses of the same risk; they appear to be two separate biological insults. A separate mouse study has linked high-salt diets to synaptic loss and memory impairment through reduced gut-derived butyrate, reinforcing the gut-microbiome route as a plausible pathway, as described in a study on high-salt diets, gut bacteria and memory.

Mice Received Transplanted Human Gut Microbiomes Before Testing

To make the gut side of the experiment relevant to human biology, researchers transplanted gut microbiomes from 10 human donors into 32 healthy male mice, creating "humanized" microbiota, then divided the animals into three diet groups for 14 weeks: a normal-salt control group (0.5% dietary salt), a low-salt group (0.1%, described as severe restriction), and a high-salt group (8.0%, described as extreme consumption). Giving all three groups the same humanized-microbiota background let the researchers isolate the effect of salt intake itself rather than pre-existing differences in gut bacteria between animals.

What This Means If You Are Watching Your Sodium

This does not mean you should abandon a doctor-recommended low-sodium diet. Current U.S. guidance still calls for keeping sodium under 2,300 milligrams a day for most adults, and the study's low-salt group was on a far more restrictive regimen than typical medical advice. But the finding is a signal that the relationship between sodium and the brain is not a straight line where less is always safer. If you are on an unusually strict salt-restricted diet, whether self-imposed or prescribed, and you notice memory or concentration changes, it is worth raising with a doctor rather than assuming the diet itself carries no risk. The mechanism here, reduced short-chain fatty acid production feeding into hippocampal synaptic protein loss, gives researchers something concrete to probe in human patients, even though no one should change a prescribed sodium target based on a mouse study alone.

The Biggest Caveat: This Has Not Been Shown in Humans

The study was conducted entirely in mice, and the salt levels tested, a diet of just 0.1% salt versus 8.0% salt, are far more extreme than what most humans eat even on restrictive or indulgent diets. Human relevance of these specific thresholds has not been established. It is also worth flagging that the full study text was not available for this article; this summary draws on the study's published abstract and detailed reporting on its findings rather than the complete paper, so details like exact statistical comparisons and secondary measures are not included here. Separately, human research has found its own links between blood sodium and cognition: a study of more than 5,000 older men found both low and high blood sodium levels were associated with cognitive decline over time, in research published in the Clinical Journal of the American Society of Nephrology, though that work measured blood sodium levels rather than dietary salt intake directly.

What Comes Next for Gut-Brain Salt Research

The researchers frame their results as evidence that excessive salt restriction is not biologically equivalent to eating a normal amount of salt, and may carry its own distinct risk pattern for cognitive health rather than simply being the "safe" end of the sodium spectrum. The logical next step is testing whether the same two-sided pattern, inflammation-driven harm from too much salt and metabolite-starvation harm from too little, shows up in human cohorts with naturally varying sodium intake, and whether restoring propionate and butyrate levels can protect memory even when salt intake stays at an extreme.

Common Questions

Does this mean eating more salt is good for my brain? No. The study did not find that high salt is safe. It found that high salt harmed memory through inflammation while low salt harmed memory through a different, non-inflammatory route. Both extremes performed worse than the normal-salt control group.

What counts as "low salt" in this study? The low-salt group received 0.1% dietary salt, a far stricter restriction than typical low-sodium medical diets, compared with 0.5% for the normal-salt control group and 8.0% for the high-salt group.

How could salt intake affect memory through the gut? Both extreme diets altered gut bacteria and reduced short-chain fatty acids like propionate and butyrate, which the researchers linked to lower levels of synaptic proteins (SYN1, PSD95, BDNF) in the hippocampus, the brain region central to memory formation.

Should I change my sodium intake based on this study? No. This was a mouse study with salt levels far more extreme than typical human diets, and the researchers themselves say human relevance is not established. Anyone on a medically prescribed sodium target should keep following their doctor's guidance.

References

1. Anji Chen, Shilong Hu, Fansen Zeng, et al. (2026). Long-term low-salt and high-salt diets differentially disrupt the gut–metabolite–brain axis and induce cognitive impairment. Food Research International. https://doi.org/10.1016/j.foodres.2026.119719
2. Ygor Parladore Silva, Andressa Bernardi, Rudimar Luiz Frozza (2020). The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. Frontiers in Endocrinology. https://doi.org/10.3389/fendo.2020.00025
3. Chao Lei, Cong Liu, Yuling Peng, et al. (2023). A high‐salt diet induces synaptic loss and memory impairment via gut microbiota and butyrate in mice. iMeta. https://doi.org/10.1002/imt2.97
4. New Research: Excess Sodium Intake Remains Common in the United States. archive.cdc.gov. https://archive.cdc.gov/www_cdc_gov/media/releases/2016/p0106-sodium-intake.html
5. Kristen L. Nowak, Kristine Yaffe, Eric S. Orwoll, et al. (2018). Serum Sodium and Cognition in Older Community-Dwelling Men. Clinical Journal of the American Society of Nephrology. https://doi.org/10.2215/cjn.07400717