Mediterranean diet intervention in overweight and obese subjects lowers plasma cholesterol and causes changes in the gut microbiome and metabolome independently of energy intake

Abstract

ObjectivesThis study aimed to explore the effects of an isocaloric Mediterranean diet (MD) intervention on metabolic health, gut microbiome and systemic metabolome in subjects with lifestyle risk factors for metabolic disease.DesignEighty-two healthy overweight and obese subjects with a habitually low intake of fruit and vegetables and a sedentary lifestyle participated in a parallel 8-week randomised controlled trial. Forty-three participants consumed an MD tailored to their habitual energy intakes (MedD), and 39 maintained their regular diets (ConD). Dietary adherence, metabolic parameters, gut microbiome and systemic metabolome were monitored over the study period.ResultsIncreased MD adherence in the MedD group successfully reprogrammed subjects’ intake of fibre and animal proteins. Compliance was confirmed by lowered levels of carnitine in plasma and urine. Significant reductions in plasma cholesterol (primary outcome) and faecal bile acids occurred in the MedD compared with the ConD group. Shotgun metagenomics showed gut microbiome changes that reflected individual MD adherence and increase in gene richness in participants who reduced systemic inflammation over the intervention. The MD intervention led to increased levels of the fibre-degrading Faecalibacterium prausnitzii and of genes for microbial carbohydrate degradation linked to butyrate metabolism. The dietary changes in the MedD group led to increased urinary urolithins, faecal bile acid degradation and insulin sensitivity that co-varied with specific microbial taxa.ConclusionSwitching subjects to an MD while maintaining their energy intake reduced their blood cholesterol and caused multiple changes in their microbiome and metabolome that are relevant in future strategies for the improvement of metabolic health.

Comprehensive Analysis of Gut Microbiota of a Healthy Population and Covariates Affecting Microbial Variation in Two Large Japanese Cohorts

“…Major host factors that have been reported to affect the gut microbial community structure include: age [8][9][10], ethnicity [11,12], geography [13], host genetics [14], gender [15], and life style factors such as dietary habits [16], smoking [17], exercise [18], and medications of non-antibiotics [19] and antibiotics [20]. Certain patterns and transitions in the gut microbiota composition are observed with age [8] and altered dietary intake [21][22][23].…”

Mediterranean diet, gut microbiota and health: when age and calories do not add up!

“…On the other hand, one may even argue that having both metagenomic and metabolomic analyses in faeces still only provides part of the complex story behind diet–host interactions. For example, in the first study discussed above,6 a profound change in the diet (ie, higher levels of fibre) led to a higher abundance of classical SCFA producers. Curiously, although higher levels of SCFAs were expected, an actual measurement in the faeces revealed that the SCFA levels remained unaffected by the diet.…”

“…In GUT , two studies conducted in humans have now made progress towards a better understanding of the role of the gut microbiota and the MedDiet in disease risk factors 6 7…”

“…In the first paper, Meslier and colleagues studied healthy overweight or obese subjects with sedentary lifestyles who habitually consumed low amounts of fruits and vegetables during an 8-week follow-up 6. In this randomised controlled study, 43 subjects were assigned to the MedDiet group, in which they received a personalised diet adapted to their habitual energy intake.…”

“…The second interesting paper published in GUT investigates the effect of a MedDiet followed for 1 year in 612 elderly non-frail and prefrail subjects across five countries 6. Ageing has been associated with changes in the gut microbiota composition and higher inflammation levels.…”