Summary: Prebiotics are digestion-resistant compounds that feed the “good bacteria” in the GI tract. The agave plant contains inulin, a polysaccharide for which some previous studies suggest a physiologic effect. Kelly Swanson, from the University of Illinois (Illinois, USA), and colleagues enrolled 29 healthy adults in a 3-period crossover double-blind study in which subjects were randomized to 1of 3 groups: 0, 5.0, or 7.5 grams per day of agave inulin; each period was followed by a 7-day washout before crossover. Fecal samples were collected and fermented, then analyzed to determine gut bacteria populations. Data analysis revealed that Bifidobacterium levels increased 4-fold after 5.0 and 7.5 grams per day agave inulin; as well, Desultivibrio levels decreased 40%. Agave inulin consumption also associated with reduced fecal pH and increased butyrate ? suggesting increased saccharolytic fermentation and reduced proteolytic fermentation. The study authors observe that: “Agave inulin supplementation shifted the gastrointestinal microbiota composition and activity in healthy adults.”
Background: Prebiotics resist digestion, providing fermentable substrates for select gastrointestinal bacteria associated with health and well-being. Agave inulin differs from other inulin type fibers in chemical structure and botanical origin. Preclinical animal research suggests these differences affect bacterial utilization and physiologic outcomes. Thus, research is needed to determine whether these effects translate to healthy adults.
Objective: We aimed to evaluate agave inulin utilization by the gastrointestinal microbiota by measuring fecal fermentative end products and bacterial taxa.
Methods: A randomized, double-blind, placebo-controlled, 3-period, crossover trial was undertaken in healthy adults (n = 29). Participants consumed 0, 5.0, or 7.5 g agave inulin/d for 21 d with 7-d washouts between periods. Participants recorded daily dietary intake; fecal samples were collected during days 16?20 of each period and were subjected to fermentative end product analysis and 16S Illumina sequencing.
Results: Fecal Actinobacteria and Bifidobacterium were enriched (P < 0.001) 3- and 4-fold after 5.0 and 7.5 g agave inulin/d, respectively, compared with control. Desulfovibrio were depleted 40% with agave inulin compared with control. Agave inulin tended (P < 0.07) to reduce fecal 4-methyphenol and pH. Bivariate correlations revealed a positive association between intakes of agave inulin (g/kcal) and Bifidobacterium (r = 0.41, P < 0.001). Total dietary fiber intake (total fiber plus 0, 5.0, or 7.5 g agave inulin/d) per kilocalorie was positively associated with fecal butyrate (r = 0.30, P = 0.005), tended to be positively associated with Bifidobacterium (r = 0.19, P = 0.08), and was negatively correlated with Desulfovibrio abundance (r = ?0.31, P = 0.004). Conclusions: Agave inulin supplementation shifted the gastrointestinal microbiota composition and activity in healthy adults. Further investigation is warranted to determine whether the observed changes translate into health benefits in human populations.
