Effects of a gluten-free diet on gut microbiota and immune function in healthy adult human subjects

Abstract

Diet influences the composition of the gut microbiota and host's health, particularly in patients suffering from food-related diseases. Coeliac disease (CD) is a permanent intolerance to cereal gluten proteins and the only therapy for the patients is to adhere to a life-long gluten-free diet (GFD). In the present preliminary study, the effects of a GFD on the composition and immune function of the gut microbiota were analysed in ten healthy subjects (mean age 30·3 years) over 1 month. Faecal microbiota was analysed by fluorescencein situhybridisation (FISH) and quantitative PCR (qPCR). The ability of faecal bacteria to stimulate cytokine production by peripheral blood mononuclear cells (PBMC) was determined by ELISA. No significant differences in dietary intake were found before and after the GFD except for reductions (P = 0·001) in polysaccharides.Bifidobacterium,Clostridium lituseburenseandFaecalibacterium prausnitziiproportions decreased (P = 0·007,P = 0·031 andP = 0·009, respectively) as a result of the GFD analysed by FISH.Bifidobacterium,LactobacillusandBifidobacterium longumcounts decreased (P = 0·020,P = 0·001 andP = 0·017, respectively), whileEnterobacteriaceaeandEscherichia colicounts increased (P = 0·005 andP = 0·003) after the GFD assessed by qPCR. TNF-α, interferon-γ, IL-10 and IL-8 production by PBMC stimulated with faecal samples was also reduced (P = 0·021,P = 0·037,P = 0·002 andP = 0·007, respectively) after the diet. Therefore, the GFD led to reductions in beneficial gut bacteria populations and the ability of faecal samples to stimulate the host's immunity. Thus, the GFD may constitute an environmental variable to be considered in treated CD patients for its possible effects on gut health.