Researchers reported that yogurt, kefir, kimchi, kombucha and other fermented foods improved microbiome diversity and reduced inflammatory markers in healthy adults during a 10-week clinical trial.
By yourNEWS Media Newsroom
A Stanford School of Medicine clinical trial has found that adding fermented foods to the diet may quickly increase gut microbiome diversity while lowering markers of inflammation, offering new evidence that everyday dietary choices can influence immune activity and digestive health.
The 10-week trial, published in Cell, randomly assigned 36 healthy adults to follow either a fermented-food diet or a high-fiber diet. Participants in the fermented-food group consumed items such as yogurt, kefir, kimchi, kombucha and other fermented foods. Those assigned to the high-fiber group increased intake of legumes, seeds, whole grains and vegetables.
Researchers tracked participants through three stages: a three-week period in which they continued their usual eating patterns, a 10-week dietary intervention and a four-week follow-up after the assigned diet ended. Blood and stool samples were collected at multiple points to measure microbial changes and immune system activity.
The fermented-food group showed a significant rise in overall gut microbiome diversity, with the strongest changes seen among participants who consumed larger servings. Researchers also found reductions in 19 inflammatory proteins, including interleukin-6, a marker associated with conditions such as rheumatoid arthritis, Type 2 diabetes and chronic stress. Four types of immune cells also showed reduced activation, according to the report.
The findings build on recent research cited by Dr. Joseph Mercola showing that fermented foods can improve gut microbiome diversity and reduce inflammatory responses linked to chronic conditions such as rheumatoid arthritis. The Stanford trial added to that evidence by comparing fermented foods directly with a high-fiber dietary approach.
Short-chain fatty acids may help explain part of the effect, according to the report. Fermented foods can contain beneficial bacteria, including strains such as Bacillus, which help process indigestible fibers and produce compounds that may reduce inflammation. The decline in inflammatory markers in the fermented-food group aligns with earlier observations that probiotic-rich foods can influence immune function.
Registered dietitian nutritionist Molly Knudsen has recommended daily fermented food consumption for microbiome support, noting that routine dietary habits play a major role in shaping gut health.
The high-fiber group did not experience the same short-term reductions in inflammatory proteins. On average, gut microbiome diversity remained stable among participants eating the fiber-rich diet. Researchers also found higher levels of carbohydrates in stool samples as fiber intake rose, suggesting that some participants’ gut microbes were not fully breaking down the added fiber.
The researchers said that result may reflect findings from other studies showing that people in industrialized societies often have lower levels of fiber-degrading gut microbes. In that context, a high-fiber diet may still be beneficial but may require more time, different microbial starting conditions or additional dietary support before measurable changes appear.
Gastroenterologist Lisa Ganjhu has said pairing fiber with polyphenols may strengthen gut health benefits. The Stanford results suggest that fiber alone may not rapidly shift microbiome diversity or inflammatory markers within a short intervention window.
Public health data show that about 95% of Americans do not consume enough fiber, underscoring the importance of fiber-rich foods even though the trial found more immediate microbiome and immune changes in the fermented-food group.
The researchers concluded that fermented foods can produce rapid and measurable changes in the gut ecosystem and inflammation-related immune markers. They said future studies will examine the molecular mechanisms behind the findings, including research in mice and trials testing whether fermented foods and fiber may work together.
Additional research is also planned in people with metabolic and immune disorders, as well as pregnant women and older adults.
The study adds to a growing body of research linking whole-food dietary patterns, fermented foods and gut health to broader wellness outcomes, including inflammation control, immune function and mental well-being. Researchers said the results support further investigation into whether fermented foods could be used therapeutically in specific patient populations.
Source: Natural News
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