The Science Behind Fermented Foods

Fermented foods, such as yogurt, sourdough bread, and kimchi, are made through intentional microbial growth, which breaks down food components, producing metabolites that alter the taste, texture, and nutritional profile of foods, while also helping to preserve them.^1,2 Fermented foods offer notable nutritional benefits. For example, natto, a traditional Japanese dish made from fermented soybeans, is high in fiber and vitamin K.³

Fermented foods have been produced by humans for thousands of years as a way to preserve and enhance foods, though modern research is still investigating their other potential health benefits.

One study, conducted by the University of California, Davis and published in April 2025 in Applied and Environmental Microbiology, examined the potential gut health benefits of fermented cabbage (sauerkraut).⁴ Fermented vegetables, the study explains, enrich metabolome profiles with beneficial compounds that are also made by the human gut microbiome. After testing store-bought sauerkraut, laboratory-fermented sauerkraut in a cell model, and raw cabbage and its brine, the researchers found Intestinal epithelial barrier-protective bioactivity in the fermented cabbage samples, suggesting potential for protection against inflammation.

The study author, Maria Marco, PhD, presented on fermented foods and bioactive metabolites at this year’s Natural Products Expo West. “Fermented foods, plants, and dairy provide a complete package of beneficial microbes and compounds, and fermented foods can support gut health, especially intestinal barrier function,” she emphasized. Microbes are an essential part of the fermentation process, she explained, noting that microbes change food in several ways, such as breaking down proteins and polysaccharides into units that are easier to digest, removing toxic compounds, delivering bioactive compounds, including vitamins, and increasing the number of living microbes.

Other potential mechanisms for fermented foods, including their use as a clinical tool, have also been the subject of expanding research. A systematic review published in January 2026 in Frontiers in Nutrition examined the potential for fermented foods to reduce reactions to food allergies in children and adults.⁵ Fermentation, the study notes, involves microbial activity of microorganisms that preserve food while also enhancing nutrient bioavailability. This review examined studies involving soy products, baked goods, fruit-based beverages, vinegar-treated foods, oat-based drinks, and dairy products like yogurt and cheese. While the researchers found that some fermented foods showed potential to reduce allergenicity, the results were ultimately inconsistent, and additional rigorous trials were needed to better understand the role of fermented foods in combating food allergies.

The presence of microbes in fermented foods and beverages does confer gut health benefits, though the consumption of fermented foods is not synonymous with probiotic supplementation. Probiotics are specific bacteria known to provide health benefits, and the microbes in fermented foods rarely fall under the criteria for probiotics. Therefore, supplementation with probiotics is an important option for more targeted digestive support, while fermented foods remain a time-tested option for supporting overall digestive wellness.

References

1. International Scientific Association for Probiotics and Prebiotics. Fermented foods. Accessed March 13, 2026. https://isappscience.org/resource/fermented-foods/
2. Stanford Medicine. The science of fermented foods. Accessed March 16, 2026. https://med.stanford.edu/nutrition/education/Resources/Fermenting-the-Facts/the-science-of-fermented-foods.html.
3. Healthline. 8 fermented foods and drinks to boost digestion and health. Accessed March 13, 2026. https://www.healthline.com/nutrition/8-fermented-foods
4. Wei L, Marco ML. The fermented cabbage metabolome and its protection against cytokine-induced intestinal barrier disruption of Caco-2 monolayers. Appl Environ Microbiol. 2025;91(5):e0223424. doi:10.1128/aem.02234-24
5. Hyseni B, Papadimitriou K, Issa A, et al. The role of fermented foods in managing food allergies in children and adults: a systematic review. Front Nutr. 2026;12:1689636. doi:10.3389/fnut.2025.1689636