gluten-free diet affects gut microbiota and immune function in healthy adult human subjects

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*1: Br J Nutr. 2009 May 18:1-7. [Epub ahead of print]

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*Effects of a gluten-free diet on gut microbiota and immune function in

healthy adult human subjects.*

De Palma G, Nadal I, Collado MC, Sanz Y.

Microbial Ecophysiology and Nutrition Group, Institute of Agrochemistry

and Food Technology (IATA), Spanish National Research Council (CSIC), PO

Box 73, 46100 Burjassot, Valencia, Spain.

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 fluorescence in situ hybridisation

(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 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

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 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. 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.