Relationship between the Gluten-Free Diet and the Gut Microbiota

“The human intestinal tract harbors a collection of beneficial bacteria (symbi- onts/mutualists) that perform an array of functions, including the provision of attri- butes not encoded in the human genome. This ecosystem is greatly influenced by the diet, which constitutes a major environ- mental factor driving bacterial diversity. Therefore, long-term dietary practices for treating food-related diseases might affect the composition of the resident microbiota and, thereby, its functional relationships with diverse host organs and tissues. In particular, intestinal bacteria constitute a constant challenge of antigens to their host that modulate mucosal immunity and the primary line of defence against antigens acquired orally. Celiac disease appeared as a result of dietary changes associated with the development of the agriculture and cereals cultivation. This is a chronic enteropathy caused by an aberrant immune response to cereal gluten proteins and, still the only therapy for the patients is to exclude the gluten from the diet. Although the adherence to a strict gluten-free diet (GFD) usually leads to the remission of the major clinical symptoms, nutritional deficiencies and health complications are often reported in treated patients. In addition, the microbiota of patients under a GFD is not completely restored in comparison with that of healthy subjects. In this context, we published a preliminary study to establish whether the GFD in itself could lead to modifications on the composition and immune properties of the gut microbiota. This study included 10 healthy subjects (30.3 years-old), who were following a GFD over one month by replacing the gluten-containing foods they usually ate with certified gluten-free foods (with no more than 20 parts per million of gluten). Analyses of fecal microbiota and dietary intakes, indicated that populations of generally regarded healthy bacteria decreased (Bifidobacterium, B. longum and Lactobacillus), while populations of potentially unhealthy bacteria increased parallel to reductions in the intake of polysaccharides (from 117 g to 63 g on average) after following the GFD. In particular, increases were detected in numbers of E. coli and total Enterobacteriaceae, which may include opportunistic pathogens. This evidence suggests a disruption of the delicate balance between the host and its intestinal microbiota (dysbiosis), which might favor the overgrowth of opportunistic pathogens and weaken the host defences against infection and chronic inflammation via possible alterations in mucosal immunity.

Effects of a gluten-free diet on gut microbiota and immune function in healthy adult humans.
Yolanda Sanz. Microbial Ecophysiology and Nutrition Group; Institute of Agrochemistry and Food Technology (IATA); Spanish National Research Council (CSIC); Valencia, Spain. Gut Microbes 1:3, 135-137; May/June 2010; © 2010 Landes Bioscience”.