Calorie-restricted oat diet is associated with zonulin and short-chain fatty acid response in metabolic syndrome: a randomized controlled trial

Oats are associated with positive effects on gut health, but human studies are largely lacking. Therefore, we investigated the effects of two different oat diets on gut permeability makers in individuals with metabolic syndrome, each in a randomized, controlled parallel design. Participants either consumed 3 × 100 g oatmeal/d for 2 d or an adapted control diet, or they integrated 1 × 80 g oatmeal/d into their habitual diet for 6 weeks or maintained it unchanged. Serum zonulin decreased upon 2-d calorie-restricted oat diet compared to baseline, while plasma butyric acid increased compared to the control (n = 27). Zonulin reduction correlated inversely with changes in short-chain fatty acids (SCFAs), particularly valeric and butyric acids, which were associated with shifts in microbial composition. During the 6-week isocaloric oat diet, these parameters remained stable (n = 22). Our data suggests that alterations in microbiome and related effects on SCFAs upon a short-term calorie-restricted diet with high-dose oats are contributing factors to changes in gut permeability markers. Thus, an intense oat intake might be a suitable and feasible approach to improve obesity-related intestinal barrier dysfunction in metabolic syndrome.