Amounts and Botanical Diversity of Dietary Fruits and Vegetables Affect Distinctly the Human Gut Microbiome

Abstract Objectives While increasing fruit and vegetable (FV) intake is a near-universal recommendation for improved health outcomes, information on dietary FV amount and diversity impact on health biomarkers is scarce. FV are a major dietary source of gut microbiota (GM) accessible carbohydrates and phytochemicals, however, most studies have focused on single food items or their extracted components, with few holistic studies available. Here, two separate randomized dietary interventions were used to assess the impact of low vs high FV intake and low vs high botanical diversity on GM profiles in healthy adults. We hypothesized that increasing FV would result in beneficial modulations to GM with further increases benefits in those consuming FV from diverse botanical families. Methods Study 1 was a crossover design with, 11 males randomized to starting diets of low FV (L) or high FV (H) over 9 days. Stool samples were obtained at day 0, 3, 6 and 9 of each treatment period. In Study 2, 21 individuals were provided a low FV (L) lead-in diet for 4 days and then randomly assigned to a high FV diet with either low (LB; 11 families) or high botanical diversity (HB; 24 families) for an additional 4 days. Stool was collected at baseline, and after each diet intervention. GM was analyzed using 16S rRNA sequencing performed on an Illumina MiSeq. The Mothur pipeline was used for preliminary data analysis, followed by statistical analyses in PAST. Results In Study 1, the L treatment resulted in minimal microbiota alterations, while a significant increase in Bacteroidetes and decrease in Firmicutes (which peaked at day 6) was observed in the H group. Intriguingly, the L group experienced a short-term increase in Bifidobacterium and Lactobacillus, and both treatments incurred significant increases in Bacteroides and Akkermansia and a decline of Faecalibacterium. In study 2 the transition from low to high FV resulted in similar trends than in Study 1. However, the HB treatment resulted in a more diverse GM, characterized by increased relative abundances of beneficial Firmicutes (Lachnospiraceae, Faecalibacterium and Clostridium XIVa). Conclusions Our results suggest that both amounts of FV consumed and botanical diversity modulate the GM. Determining better FV combinations from a GM perspective thus appears as a possible task for future research. Funding Sources Colorado Agriculture Experiment Station.