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This study aimed to explore the potential associations of adherence to the Mediterranean diet with gut microbiota characteristics and gastrointestinal symptomatology in an adult population. Other long-term dietary habits (e.g. consumption of snacks and junk food or stimulant intake) were also evaluated in terms of the gut microbiota profile. Participants (n 120) underwent anthropometric, dietary, physical activity and lifestyle evaluation. Adherence to the Mediterranean diet was assessed using a Mediterranean diet score, the MedDietScore, and subjects were classified into three tertiles according to individual adherence scoring. Gut microbiota composition was determined using quantitative PCR and plate-count techniques, and faecal SCFA were analysed using GC. Gastrointestinal symptoms were also evaluated. Participants with a high adherence to the Mediterranean diet had lower Escherichia coli counts (P=0·022), a higher bifidobacteria:E. coli ratio (P=0·025), increased levels and prevalence of Candida albicans (P=0·039 and P=0·050, respectively), greater molar ratio of acetate (P=0·009), higher defaecation frequency (P=0·028) and a more pronounced gastrointestinal symptomatology compared with those reporting low adherence. A lower molar ratio of valerate was also observed in the case of high adherence to the Mediterranean diet compared with the other two tertiles (P for trend=0·005). Positive correlations of MedDietScore with gastrointestinal symptoms, faecal moisture, total bacteria, bifidobacteria:E. coli ratio, relative share of Bacteroides, C. albicans and total SCFA, as well as negative associations with cultivable E. coli levels and valerate were indicated. Fast food consumption was characterised by suppressed representation of lactobacilli and butyrate-producing bacteria. In conclusion, our findings support a link between adherence to the Mediterranean diet and gut microbiota characteristics.

Diet, among other environmental and genetic factors, is currently recognised to have an important role in health and disease. There is increasing evidence that the human colonic microbiota can contribute positively towards host nutrition and health. As such, dietary modulation has been proposed as important for improved gut health, especially during the highly sensitive stage of infancy. Differences in gut microflora composition and incidence of infection occur between breast- and formula-fed infants. Human milk components that cannot be duplicated in infant formulae could possibly account for these differences. However, various functional food ingredients such as oligosaccharides, prebiotics, proteins and probiotics could effect a beneficial modification in the composition and activities of gut microflora of infants. The aim of the present review is to describe existing knowledge on the composition and metabolic activities of the gastrointestinal microflora of human infants and discuss various possibilities and opportunities for its nutritional modulation.

Anaerobic batch culture fermenters were used for a preliminary screening of the in vitro utilization by human gut microflora of dextran and novel oligodextrans (I, II and III) produced in the University of Reading (UK). Glucose and fructooligosaccharides (FOS) were used as reference carbohydrates. As expected, FOS acted as a good prebiotic in that it selectively increased numbers of bifidobacteria in the early stages of the fermentation. Dextran and oligodextrans each resulted in an enrichment of bifidobacteria in the batch cultures, with high levels of persistence up to 48 h. They also produced elevated levels of butyrate ranging from 5 to 14.85 mmol/l. To more effectively simulate conditions that prevail in different regions of the large intestine, a three-stage continuous culture cascade system was used to study further the fermentation of dextran, a low-molecular-mass oligodextran (IV) and maltodextrin. Oligodextran IV was shown to be the best substrate for bifidobacteria and lactobacilli with steady-state populations of bifidobacteria and lactobacilli being higher in all three vessels of the gut model than the respective populations resulting from dextran and maltodextrin. A maximum difference of 1.9 log was observed in vessel 1 for both bifidobacteria and lactobacilli in the case of dextran fermentation, with 1.4 log and 0.8 log in vessel 3 were the maximum differences for bifidobacteria and lactobacilli when maltodextrin was used as the carbohydrate source. Moreover, dextran and oligodextran appeared to stimulate butyrate production, with a maximum production up to 25.39 mmol/l in vessel 3 when fermenting dextran, followed by 21.70 mmol/l in the case of oligodextran IV and only 12.64 mmol/l in the case of maltodextrin.