Mediterranean diet: the missing link between gut microbiota and inflammatory diseases

Diet, gut microbiota and chronic inflammatory diseases are closely related. Indeed, study findings have reported that food assumption strongly affects microbial intestinal composition and metabolism; in turn, gut microbiota dysbiosis has recently emerged as a key determinant for several inflammatory diseases, including obesity, metabolic syndrome, diabetes, as well as chronic inflammatory diseases of human gastrointestinal tract.1 In particular, weak levels of fibers from diet have been identified to bring long-term alteration in gut microbiota production of compounds involved in the modulation of immune and inflammatory responses, including short-chain fatty acids as butyrate, polysaccharide A and peptidoglycans.2 As expected, epidemiological studies have recognized right ‘Western diet’ patterns, typical of developing countries and characterized by a low assumption of vegetables, fruit and fish along with high levels of red meat, as the main responsible for the increased incidence of chronic inflammatory diseases in the past decades.3 Therefore, a nutraceutical intervention targeting intestinal microbiota could represent an interesting opportunity for chronic inflammatory disease prevention and treatment. What is, then, the so called ‘missing link’? As only recently supported by scientific evidence, a shift toward Mediterranean dietary patterns (MDPs), UNESCO ‘Intangible Cultural Heritage of Humanity’, represents nowadays not only a choice of health and well-being, but, mainly, an absolute scientifically recognized and widely accepted valid instrument able to produce clear benefits for the management of several pathologies and an overall reduction of mortality. Indeed, MDP represents a balanced nutritional diet, characterized by the consumption in high amounts and frequency of the most important source of fibers (cereals, legumes, vegetables, fruits and nuts) and chemical compounds with anti-oxidative properties (flavonoids, phytosterols, vitamins, terpenes and phenols). Furthermore, high levels of oleic acid, polyphenols and monounsaturated fatty acids from olive oil intake, provides remarkable anti-atherogenic and anti-inflammatory actions.4 Improvement in inflammation biomarkers (C-reactive protein and the micronuclei assay content), as well as in gene expression profile which results from a transcriptomic approach, have been demonstrated not only in healthy people subjected to a Mediterranean-inspired diet5 but, as recently revealed in a pilot study, also in a population affected by Crohn's disease, a chronic inflammatory intestinal disorder. More interestingly, a MDP adherence was accompanied by a ‘normalization’ trend of gut microbiota, characterized by an increase of Bacteroidetes and Clostridium clusters and reduction in Proteobacteria and Bacillaceae bacterial phyla.6 Although a deeper elucidation of the mutual relationship among diet, gut microbiota and chronic inflammatory diseases remains to be achieved through integrated epidemiological and transcriptomic tools, more than a speculation has actually been advanced. Indeed, in our opinion Mediterranean diet constitutes an intriguing and promising approach to address inflammation-driven perturbation in gut microbiota.

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Correspondence to M Bifulco.

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Bifulco, M. Mediterranean diet: the missing link between gut microbiota and inflammatory diseases. Eur J Clin Nutr 69, 1078 (2015). https://doi.org/10.1038/ejcn.2015.81

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