Beneficial effects of a Mediterranean diet in overweight and obese subjects after only 4 weeks of nutritional intervention

The role of diet in influencing the gut microbiome composition is widely recognized along with the outstanding effects of gut microbial activities on human health. The MD is recognized by UNESCO as an intangible cultural heritage. It is a nutritionally recommended dietary pattern characterized by high-level intake of fruit, vegetables, legumes, nuts, minimally processed cereals, moderately high consumption of fish, low intake of saturated fat, meat and dairy products, regular but moderate consumption of red wine and extra virgin olive oil as the main fat. MD can be beneficial for both prevention and treatment of several diseases such as obesity, type II diabetes, inflammatory diseases, colorectal cancer and cardiovascular diseases.

The researchers monitored dietary variables, metabolic parameters, gut microbiome and systemic metabolome in eighty-two healthy overweight and obese subjects with a habitually low intake of fruit and vegetables and a sedentary lifestyle participating in a parallel 8-week randomized controlled trial. Participants in the MedD group consumed an individually tailored diet based on typical foods of the MD without changes in energy and macronutrient intake of the habitual diet while control subjects maintained their habitual diet.

The investigation showed distinct microbial and metabolic profiles between the two groups according to diets. Significant reductions in plasma cholesterol and fecal bile acids were achieved in the MedD. Compliance to the intervention assessed through food diaries and metabolome analysis of urine, serum and faeces samples. Increased MD adherence in the MD group corresponded to higher levels of dietary biomarkers of fruit, vegetables, wholegrain cereal products, legumes, nuts and fish, along with a reduction of plasma and urinary carnitine as a consequence of reduced intake of foods of animal origin.

Switching to a MD increases gene richness in individuals with reduced inflammation accompanied by a rise in the fibre-degrading Faecalibacterium prausnitzii and a decrease of potentially proinflammatory species such as Ruminococcus gnavus.

Microbial metabolites of importance for human health were also measured. Increase in the levels of the anti-inflammatory urolithins was observed. Such compounds derive from gut microbial metabolism of ellagitannins, belonging to the family of polyphenols that are abundant in the nuts, which were daily consumed by the subjects during the nutritional intervention. Consistent links were highlighted between production of urolithins and their microbial producers in the gut (Eggerthellaceae).

A MD-tailored dietary intervention can be also helpful in getting clinical advantages such as ameliorating insulin sensitivity in individuals harboring lower baseline levels of Prevotella copri.

The findings are in line with the concept of personalized responses to dietary interventions and are relevant for clinical practice in the era of precision medicine and individualized nutrition, the researchers point out.

MD may remodel the gut microbiome towards a state that promotes metabolic and cardiovascular health in obese individuals, and such effects maybe potentiated under caloric restriction. The findings contribute to improve the knowledge on the mechanisms through which it is possible to modulate microbiome activities with ad hoc nutritional interventions to potentiate the clinical outcomes, they conclude.

The study was implemented within the DINAMIC (Diet-Induced Arrangement of the gut Microbiome for the Improvement of Cardiometabolic health) project funded by the European Joint Programming Initiative “A Healthy Diet for a Healthy Life” (JPI HDHL) - Joint Action “Intestinal Microbiomics”.

The study was implemented within the DINAMIC (Diet-Induced Arrangement of the gut Microbiome for the Improvement of Cardiometabolic health) project funded by the European Joint Programming Initiative “A Healthy Diet for a Healthy Life” (JPI HDHL) - Joint Action “Intestinal Microbiomics”.

http://www.jpi-dinamic.wzw.tum.de/

The authors

The nutritional intervention has been carried out at the University of Naples Federico II and involved multidisciplinary expertise in the research groups of Prof. Danilo Ercolini and Paola Vitaglione at the University of Naples (IT), Prof. Lars Dragsted and Henrik Roager at the University of Copenhagen (DK) and Prof. Dusko Ehrlich at the MetaGenoPolis research centre (FR).

Reference

V. Meslier^*, M. Laiola^*, H.M. Roager^*, F. De Filippis, H. Roume, B. Quinquis, R. Giacco, I. Mennella, R. Ferracane, N. Pons, E. Pasolli, A.A. Rivellese, L.O. Dragsted, P. Vitaglione, D.S. Ehrlich, D. Ercolini. “Mediterranean diet intervention in overweight and obese subjects lowers plasma cholesterol and causes changes in the gut microbiome and metabolome independently of energy intake”, Gut 2020.

http://dx.doi.org/10.1136/gutjnl-2019-320438

^*equal contributions