High Salt Intake Linked to Gut Microbiome Shifts in 9,220 Adults

The salt shaker on your dinner table may be doing more than raising your blood pressure. A large cross-sectional study from Sweden, published in Frontiers in Nutrition, found that people who excreted more sodium per day had measurably different gut bacteria than those who excreted less – including fewer Akkermansia muciniphila, a bacterium tied to gut barrier health, and more oral-associated bacteria independently linked to heart disease risk. The study is the first large-scale human analysis to use full shotgun metagenomic sequencing for this question, and the sample size alone – 9,220 adults – places it in a different category from prior work.

Key Takeaways

• In 9,220 Swedish adults, higher estimated daily sodium excretion was linked to 75 specific gut bacterial shifts, including lower Akkermansia and fewer fiber-fermenting bacteria from the Lachnospiraceae and Ruminococcaceae families.
• Higher sodium was also associated with more oral-associated bacteria – Streptococcus, Veillonella, and Actinomyces – appearing in the gut, a pattern previously linked to atherosclerosis in the same cohort.
• The alpha diversity link largely disappeared after adjusting for BMI, meaning body weight may explain or mediate much of that association.
• This is an observational study and cannot establish whether salt causes these microbiome changes or whether other factors in high-salt diets are responsible.

Higher Sodium Excretion Linked to 75 Gut Bacterial Species in 9,220 Adults

The core finding comes from a cross-sectional analysis of participants in SCAPIS (the Swedish CArdioPulmonary bioImage Study), a deeply characterized cohort of randomly selected Swedes aged 50-64. Researchers estimated each participant's daily sodium excretion using the Kawasaki formula – a validated urine-based calculation that converts a single morning urine sample into a 24-hour sodium estimate, used as a proxy for salt consumption. Gut microbiome profiles were generated using shotgun metagenomic sequencing (which reads all genetic material in a fecal sample to identify bacterial species and their functional pathways, as distinct from older targeted-marker approaches).

After adjusting for age, sex, BMI, blood pressure, diabetes, smoking, and detailed dietary variables, 75 bacterial species showed statistically significant associations with estimated sodium excretion. Twenty-seven showed lower abundance in people with higher sodium – most notably Akkermansia muciniphila, members of the Lachnospiraceae and Ruminococcaceae families (both associated with short-chain fatty acid production, the chemical outputs of fiber fermentation that fuel the gut lining), and several anaerobic species involved in butyrate production and epithelial support.

Salt and Oral Bacteria in the Gut: A Possible Bridge to Cardiovascular Risk

Higher sodium was linked to increased gut abundance of oral-associated taxa, including genera such as Streptococcus, Veillonella, and Actinomyces. This pattern is sometimes called "oralization" of the gut microbiome and has attracted growing attention in cardiometabolic research. A prior analysis from the same SCAPIS cohort found these oral gut bacteria correlated with prevalent atherosclerosis (arterial plaque buildup). Streptococcal DNA has also been reported in atherosclerotic plaques in multiple independent studies, pointing to a plausible biological pathway from mouth-to-gut microbial translocation to vascular disease. Animal studies have linked high-salt-induced gut dysbiosis to aggravated atherosclerosis through increased absorption of saturated fatty acids – a mechanistic thread that may eventually connect sodium exposure to these microbiome patterns in humans, though that causal chain remains unproven.

How the Study Was Designed: Shotgun Metagenomics in a Major Swedish Cohort

The analytical credibility here comes from scale and methodology. 9,220 participants is exceptional for microbiome research, and shotgun metagenomics provides taxonomic and functional resolution that older 16S rRNA gene sequencing studies cannot match. Researchers applied three increasingly stringent statistical models: the first adjusted for age and sex only; the second added BMI; the third added blood pressure, diabetes, smoking, kidney function, cholesterol, energy intake, meat intake, and macronutrients. The Bacillota/Bacteroidota ratio (a rough summary measure of gut microbial balance, formerly called the Firmicutes/Bacteroidetes ratio) was positively associated with sodium in the minimally adjusted model, consistent with animal studies showing high-salt depletion of lactic-acid-producing bacteria, but the association lost statistical significance in the fully adjusted model.

Why BMI Clouds the Diversity Picture

One of the study's most instructive findings involves alpha diversity – the within-person richness and evenness of gut bacteria. In the minimally adjusted model, higher sodium was significantly associated with lower Shannon diversity index (beta = -0.021, p < 0.001). Adding BMI substantially shrank that association (beta = -0.009, p = 0.018), and it was no longer significant in the fully adjusted model. BMI accounted for a large part of the apparent diversity effect. BMI either confounds the relationship (high-salt eaters tend to have higher BMIs, which independently affects the microbiome) or mediates it (sodium may influence the microbiome partly by influencing body weight). Either interpretation limits how directly you can attribute any diversity differences to salt alone.

What These Findings Mean for People Managing Gut or Metabolic Health

The link to fewer Akkermansia and beneficial SCFA producers is biologically plausible and directionally consistent with prior animal experiments, but it falls well short of establishing that cutting salt will restore those bacteria. Beta diversity was statistically significant across all models, but the explained variance was tiny (R² < 0.001), meaning sodium accounts for a negligible fraction of total microbial community variation. Research on Akkermansia muciniphila's role in cardiovascular protection highlights why its potential depletion matters – the bacterium supports gut barrier integrity and produces metabolites that may protect against metabolic disease – but whether the sodium-Akkermansia link is directly causal, mediated by BMI, or driven by overall dietary quality is not answered here. The cohort consisted exclusively of Swedish adults aged 50-64, which limits generalizability to younger adults and non-European populations.

What Comes Next: Interventional Studies Are the Critical Next Step

The authors call for randomized controlled trials in which sodium intake is directly manipulated and microbiome changes tracked over time. The species-level signals here – Akkermansia loss, oral-associated taxa gain, shifts in carbohydrate fermentation pathways – provide a concrete research map. Whether those bacterial changes respond specifically to sodium reduction, or to the broader dietary shifts that come with eating less processed food, is the question an interventional design can begin to answer.

Common Questions

What is Akkermansia muciniphila and why does its loss matter? Akkermansia muciniphila is a gut bacterium that lives in the colon's mucus layer, supporting mucin turnover and sustaining butyrate-producing bacteria nearby. Lower Akkermansia has been linked in other research to increased intestinal permeability and worse metabolic outcomes, though it is not yet an established clinical biomarker for any specific disease.

Does this mean a low-sodium diet improves gut health? Not based on this study alone. The research is observational and cannot establish causation. The bacterial differences seen could reflect the overall food environment of high-sodium diets rather than sodium per se. Randomized trial data would be needed before making that claim.

Is the overall effect on gut community composition large? No. Beta diversity was statistically significant but explained less than 0.001 of the variance in microbial community composition. Gut microbiome composition is shaped by many factors simultaneously; sodium, if it is a driver at all, appears to be a minor one at the population level.

References

1. Jonas Wuopio, Tiscar Graells, Yi-Ting Lin, et al. (2026). Associations between sodium intake and gut microbiota composition. Frontiers in Nutrition. https://doi.org/10.3389/fnut.2026.1889723
2. High-Salt Diet and Gut Dysbiosis Aggravate Atherosclerosis in Mice. NIH. https://pmc.ncbi.nlm.nih.gov/articles/PMC11936735/
3. High-Salt Diet Depletes Lactic Acid-Producing Gut Bacteria in Mice. NIH. https://pmc.ncbi.nlm.nih.gov/articles/PMC8950745/
4. Akkermansia muciniphila and Cardiovascular Disease: Opportunities and Challenges. NIH. https://pmc.ncbi.nlm.nih.gov/articles/PMC12867613/