Comment: Spanish researchers recently found a gluten-free diet (GFD) led to reductions in beneficial gut bacteria populations and the ability of faecal samples to stimulate the host’s immunity (Br J Nutr. 2009). The effects of a GFD on the composition and immune function of the gut microbiota were analysed in 10 healthy subjects (mean age 30.3 years) over a period of one month. No significant differences in dietary intake were found before and after the GFD except for reductions (P=0.001) in polysaccharides. Bifidobacterium, Clostridium lituseburense and Faecalibacterium prausnitzii proportions decreased (P=0.007, P=0.031 and P=0.009, respectively) as a result of the GFD analysed by fluorescence in situ hybridisation (FISH). Bifidobacterium, Lactobacillus and Bifidobacterium longum counts decreased (P=0.020, P=0.001 and P=0.017, respectively), while Enterobacteriaceae and Escherichia coli counts increased (P=0.005 and P=0.003) after the GFD assessed by quantitative PCR (qPCR). TNF-alpha, interferon-gamma, IL-10 and IL-8 production by PBMC stimulated with faecal samples was also reduced (P=0.021, P=0.037, P=0.002 and P=0.007, respectively) after the diet. The GFD may constitute an environmental variable to be considered in treated Coeliac disease (CD) patients for its possible effects on gut health.
Clinical comment: The changing of diet and effect on bacterial composition is a well recognised adaptation by the hosts ecology, especially when fibre is limited. The outcome of this intervention was a reduction of proinflammatory cytokines and a reduction in IL-10 the main anti-inflammatory cytokine. This may reflect a reduced need for IL-10as total inflammation declined, or may reflect an inability of the remaining dominant bacterial species to provide the reciprocal anti-inflammatory support. The duration of this trail was quite short indicating the remarkable plasticity of the human microbial ecology and the potential for rapid changes to effect immune health in the gut.
Giada De Palma, Inmaculada Nadal, Maria Carmen Collado and Yolanda Sanz Effects of a gluten-free diet on gut microbiota and immune function in healthy adult human subjects. British Journal of Nutrition, Published online by Cambridge University Press 18 May 2009 View Abstract