Fermented foods such as kimchi, yoghurt, sauerkraut, kefir, and miso are gaining attention for their impact on health. Earlier this year, the US government released dietary guidelines recommending these foods for better gut health, marking the first time such advice has been included.

Fermented foods are defined as any foods or drinks transformed by microbes like yeast, bacteria, and fungi, which preserve and infuse them with distinctive flavors, explained Robert Hutkins, emeritus professor of food science at the University of Nebraska-Lincoln. Maria Marco, a professor at the University of California, Davis, noted that even chocolate and some coffee undergo fermentation.

Studies show that after 10 weeks, individuals consuming fermented foods had significantly lower levels of inflammatory markers in their blood and more diverse gut microbes—both linked to reduced chronic disease risk—compared to those consuming fiber alone.

However, some research indicates higher rates of stomach and esophageal cancers in East Asian populations with high intake of kimchi and other fermented vegetables, according to Suzanne Devkota, director of the Cedars-Sinai Human Microbiome Research Institute.

Dr. Sean Spencer, a gastroenterologist and microbiome scientist at Stanford, highlighted emerging evidence that molecules produced during fermentation may reduce inflammation, regulate blood sugar, and promote satiety, although these effects have mainly been observed in animal and laboratory studies.

Marco also mentioned hypotheses that exposure to “friendly” microbes in fermented foods might train the immune system to tolerate harmless microbes or allergens while remaining responsive to harmful ones.

These insights reflect a growing scientific interest in understanding how fermented foods influence human health.

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