Abstract: Objective: To investigate the regulatory effect of fermented oat on immunity and gut health in healthy adults in order to provide scientific evidence supporting dietary recommendations to enhance immune function and gut health. Methods: A total of 75 healthy adults aged 50–65 years were recruited and randomly assigned to three groups: a control group (15 g/day of unfermented oat), a low-dose group (5 g/day of fermented oat), and a high-dose group (15 g/day of fermented oat) and the intervention period lasted for 30 days. Blood and fecal samples were collected before and after the intervention to assess immune-inflammatory factors and gut microbiota, and questionnaires were used to record bowel movement conditions. Results: Fermented oat intervention significantly improved bowel movement satisfaction in healthy adults. The intervention effectively reduced the serum levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α). Furthermore, fermented oats significantly increased the levels of Bifidobacterium and Lactobacillus in the gut. Conclusion: Fermented oat can enhance physical sensation of defecation, modulate immune-inflammatory factor levels, and promote the proliferation of beneficial gut bacteria in healthy adults. In summary, fermented oat is a healthy cereal product with postbiotic activity.

Key words: fermented oat, human trial, gut health, immune regulation, postbiotics