Avocado Consumption Alters Gastrointestinal Bacteria Abundance and Microbial Metabolite Concentrations among Adults with Overweight or Obesity: A Randomized Controlled Trial

Abstract

Background Avocados are rich in dietary fiber and monounsaturated fatty acids (MUFAs), nutrients that have been independently connected to metabolic health benefits and the gastrointestinal microbiota. Objectives We aimed to evaluate the impact of avocado consumption on the gastrointestinal microbiota and microbial metabolites, secondary outcomes of the Persea americana for Total Health (PATH) study, and conduct exploratory analyses to assess relations between the fecal microbiota, fecal metabolites, and health markers. Methods Adults [n = 163, 25–45 y, BMI (kg/m2) ≥ 25.0] were enrolled in the PATH study, a 12-wk investigator-blinded trial where participants were batch randomized to match the 2 groups by age, sex, visceral adiposity, and fasting glucose concentrations. Participants consumed isocaloric meals with or without avocado (175 g, men; 140 g, women) once daily for 12 wk. The fecal microbiota was assessed with 16S ribosomal RNA gene (V4 region) sequencing and analysis using DADA2 and QIIME2. Fecal fatty acid and bile acid concentrations were quantified using GC and LC-MS. Per-protocol (≥80% meal consumption) and intent-to-treat analyses were conducted using univariate ANOVA and Mann-Whitney U tests. Bivariate correlations were conducted between fecal microbiota, fecal metabolites, and health measures. Results The avocado treatment increased ɑ diversity and enriched Faecalibacterium, Lachnospira, and Alistipes between 26% and 65% compared with the control group. The avocado group had 18% greater fecal acetate, 70% greater stearic acid, and 98% greater palmitic acid concentrations than the control group, while the concentrations of the bile acids cholic and chenodeoxycholic acid were 91% and 57% lower, respectively. Conclusions Daily avocado consumption resulted in lower fecal bile acid concentrations, greater fecal fatty acid and SCFAs, and greater relative abundances of bacteria capable of fiber fermentation, providing evidence that this nutrient-dense food affects digestive physiology, as well as the composition and metabolic functions of the intestinal microbiota. This trial was registered at www.clinicaltrials.gov as NCT02740439.

Fecal Bacteria as Biomarkers for Predicting Food Intake in Healthy Adults

“…was increased with almond and avocado intake and identified as a predictive feature in the current report ( 10 , 11 ). Furthermore, participants who consumed avocado had enriched Faecalibacterium ( 11 ). Others have also reported increased abundances of Lachnospira spp.…”

“…For example, walnut consumption resulted in reductions in the microbially derived secondary bile acids, deoxycholic acid and lithocholic acid ( 9 ). Participants who consumed avocado had lower concentrations of the bile acids, cholic and chenodeoxycholic acid, than controls ( 11 ). These unique host–microbe interactions, which are facilitated by the nutrients in specific foods, contribute to the signatures of food consumption and ability to create a panel of fecal bacterial biomarkers of food intake.…”

“…Metabolically healthy adults ( n = 163; 25–45 y, BMI: 23.9–58.8) underwent an investigator-blinded, parallel-arm, randomized, controlled trial (NCT02740439), as previously described ( 11 , 29 ). Participants consumed isocaloric meals with or without avocado once daily for 12 wk.…”

“…Fecal samples were collected at the beginning and end of each dietary period for all 5 studies. Fecal sample collection, DNA extraction, and 16S ribosomal RNA (rRNA) gene (V4 region) sequencing were conducted as previously described ( 11 ). There was a mean ± SD of 50,053 ± 37,433 sequences per sample (range: 3764–373,284).…”

“…Indeed, the measured metabolizable energy of almonds is 25% less than the estimated value using Atwater specific factors ( 6 ), the metabolizable energy from walnuts is 21% less than that predicted ( 7 ), and a grain-based diet provides ∼8% less energy than predicted ( 8 ). We previously reported that consumption of walnuts ( 9 ), almonds ( 10 ), and avocado ( 11 ) affected bacterial genera within the Firmicutes phylum, whereas broccoli ( 12 ) consumption increased the relative abundance of genera in the Bacteroidetes phylum. Research examining barley consumption revealed an increase in relative abundances of Clostridiaceae, Roseburia , and Ruminococcus ( 13 ).…”