What sauerkraut can do for your gut
Fermented foods—especially vegetables—are increasingly recognized for their positive impact on gut health, largely through their influence on the microbiome.
A recent study published in Applied and Environmental Microbiology explored how fermented cabbage (commonly known as sauerkraut) supports gut barrier integrity, focusing on its soluble metabolites and its protective effects against epithelial damage in an in vitro model.
Introduction
Fermentation is a time-tested method for preserving perishable yet nutrient-rich foods like fruits and vegetables. Converting natural carbohydrates into organic acids, alcohols, and antimicrobial compounds extends shelf life and enhances food safety.
Cabbage fermentation, seen in regional variations such as sauerkraut (Europe), suan cai (China), and curtido (Central America), involves packing shredded cabbage in brine and fermenting it at room temperature without oxygen for two to three weeks. During this time, lactic acid bacteria (LAB) thrive and outcompete other microbes.
LAB break down sugars into compounds like lactic acid, acetic acid, mannitol, and carbon dioxide—metabolites that can make up roughly 2% of the final product’s weight. The fermentation process typically begins with species like Leuconostoc mesenteroides and Weissella spp., later joined by Lactiplantibacillus plantarum and Levilactobacillus brevis.
Beyond preserving the food and enhancing its flavor and aroma, fermentation may offer health benefits. These include strengthening the gut barrier, improving immune responses, enhancing insulin sensitivity, and supporting overall metabolic health.
Fermentation also boosts the levels of beneficial compounds such as phenolics, carotenoids, and amino acid derivatives like D-phenyl lactate (D-PLA), indole-3-lactate (ILA), and γ-aminobutyric acid (GABA)—all of which have been linked to antioxidant, immunomodulatory, and anti-cancer activities.
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Despite growing interest, studies specifically examining the health effects of fermented cabbage are limited. This study set out to investigate whether fermented cabbage can help maintain the integrity of the gut lining and prevent the translocation of bacteria, antigens, and toxins into the bloodstream—a process implicated in various inflammatory and metabolic disorders, including obesity.
Study overview
Researchers aimed to compare raw cabbage with both commercially and lab-fermented sauerkraut to evaluate their effects on intestinal function.
The team used a Caco-2 cell culture model—commonly used to mimic the human intestinal barrier—and exposed the cells to inflammatory cytokines IFN-γ and TNF-α to simulate gut inflammation.
Key findings
Fermented cabbage was rich in bioactive compounds that protected the intestinal barrier from cytokine-induced damage. When a 10% concentration of fermented cabbage extract was applied, it effectively prevented the increase in gut permeability typically triggered by inflammatory signals. This protective effect was similar to that observed with a milk filtrate containing Lacticaseibacillus paracasei BL23.
This aligns with earlier studies showing that a variety of fermented foods, food extracts, and LAB strains can help preserve intestinal barrier function. Notably, raw cabbage and brine—the two core ingredients used to make sauerkraut—did not demonstrate the same protective effect.
However, while the fermented cabbage helped maintain barrier integrity, the cytokine-exposed cells still produced elevated levels of IL-8, a key inflammatory marker. Interestingly, IL-8 levels dropped when cells were treated with the commercial ferment, and even raw cabbage and brine showed a modest ability to reduce IL-8 levels.
Using gas and liquid chromatography, researchers identified 149 metabolic byproducts in raw cabbage and 333 in fermented samples. All ferments contained common end-products like sorbitol, lactic acid, and mannitol, though their overall metabolite profiles varied.
Raw cabbage was higher in sucrose, raffinose, mannose, and fructose. Commercially fermented cabbage contained more putrescine and glucose-6-phosphate than the lab-prepared version, likely due to differences in storage temperature (4°C for commercial samples).
Other variables—such as fermentation duration and the bacterial strain used—also influenced the metabolic profile. For instance, introducing probiotic strain LP8826R closely replicated the commercial ferment’s metabolome, suggesting the potential for tailored starter cultures to boost specific metabolites.
Compared to raw cabbage, sauerkraut had fewer carbohydrates but more lactic acid, fats, amino acid derivatives, and phenolics. Among the amino acid derivatives, DLA, ILA, and lactate each played a role in protecting the gut barrier, though no single compound was solely responsible. This implies a synergistic effect among multiple metabolites.
Conclusion
The study highlights that the complex mix of metabolites found in fermented cabbage offers greater protection for gut health than isolated compounds alone.
Across various types of ferments, a consistent core set of metabolites appears to help maintain intestinal barrier function under inflammatory conditions.
Future research should aim to confirm these findings across a wider range of fermented foods. Studies could examine how different starter cultures, fermentation conditions, and storage methods influence the metabolome.
Additionally, tracking inflammatory markers over time may help pinpoint the precise mechanisms through which fermented cabbage supports gut integrity.
Journal reference:
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Wei, L., Marco, M. L. (2025). The fermented cabbage metabolome and its protection against cytokine-induced intestinal barrier disruption of Caco-2 monolayers. Applied and Environmental Microbiology. doi: https://doi.org/10.1128/aem.02234-24.