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Fermented and Fiber-rich Food Study

Study Aim

There is increasing evidence of a profound link between diet and microbiome (the population of bacteria in our gut). Specifically, it is known that dietary fiber can favorably impact the microbiome. Fermented foods, such as kombucha, yogurt, and kimchi, have gained popularity as some studies have revealed potential health benefits as well as differences in microbiome composition in people consuming them compared to non-consumers. This study investigated the degree to which increased consumption of dietary fiber, compared to increased fermented food intake, could lower inflammation – a major driver of the chronic diseases affecting industrialized societies – and increase the diversity of the microbiome in healthy adults.

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Eligible Participants

  • Generally healthy adults, 18 years of age or older
  • Currently not eating more than 20 grams of fiber per day or more than 7 servings of fermented foods per week.

Study Design

Thirty-nine participants were randomized to eat either a high-fiber diet or a high-fermented foods diet for 10 weeks. Participants were asked to gradually increase either their dietary fiber or fermented food intake with a goal of adding 20 grams of fiber or 6 servings of fermented foods per day for the first 4 weeks (ramp up phase); they were then asked to maintain their highest levels of fiber/fermented foods for 6 weeks. Blood and stool samples were collected at the beginning of the study at various time points during the intervention period to examine markers of inflammation and immune function, as well as microbiome composition, function, and short-chain fatty acid (SCFA) production.

Conclusions

The results of this study showed an increase in the number and diversity of gut bacteria and a decrease in inflammatory markers in the group consuming a diet high in fermented foods. Participants with high microbial diversity at the start of the study also showed a decrease in inflammatory markers with the high fiber diet, but those with lower diversity, did not. These findings suggest that the people with low fiber intake lost the fiber-degrading microbes and the increased fiber was not being used. A longer intervention might have shown a benefit for these participants.

Research