Gut-Microbiota-Targeted Diets Modulate Human Immune Status: Fe-Fi-Fo study

(FErmented & FIber-rich FOods)

What we want to know

The purpose of this study is to learn about the relationship of dietary fiber, fermented foods, and microbiota. We believe that a higher fiber or fermented foods intake will increase the number and richness of the microbial composition in the gut and that in turn, will have an impact on markers of physical health in the human body.

Eligible Participants

Eligible participant are:

  • 18 years or older
  • Healthy

Study Design

If eligible, participants were randomized to one of two diets, each for 14 weeks (4 weeks to learn and adapt and 10 weeks to follow the diet):

  • A diet with many foods high in fiber or
  • A diet with many fermented foods


Participants were asked to

  • Attend 9 clinic visit to provide blood and stool samples and meet with the health educator
  • Maintain dietary food records throughout the study


In this study we observed an increase in the number and diversity of gut microbiota and a decrease in inflammatory markers in the group consuming a diet high in fermented foods.  

Individuals 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. The results suggests that the people with low fiber intake lost the fiber-degrading microbes and the increased fiber is not being used. A longer intervention might have shown a benefit for these participants.  

The study results were published in the journal Cell ( in  August, 2021.