Prospective Randomized, Double-Blind, Placebo-Controlled Study of a Standardized Oral Pomegranate Extract on the Gut Microbiome and Short-Chain Fatty Acids

Abstract

Punica granatum L., commonly known as the pomegranate, is an abundant source of polyphenols, including hydrolyzable ellagitannins, ellagic acid, anthocyanins, and other bioactive phytochemicals shown to be effective in defending against oxidative stress, and has immunomodulatory activities. Ellagitannins, and their hydrolyzed product ellagic acid, interact with the gut microbiota to yield secondary metabolites known as urolithins that may have health benefits. The objective of this study was to determine the effects of supplementation with a standardized punicalagin-enriched pomegranate extract, Pomella^® (250 mg), on the gut microbiome, circulating short-chain fatty acids, and gut microbial-derived ellagitannin metabolite urolithins. A randomized, double-blind, placebo-controlled study was conducted over 4 weeks on healthy volunteers aged 25-55 years. Subjects were randomly assigned to receive either an oral supplement containing 75 mg of punicalagin or an oral placebo. Stool sample collection and venipuncture were performed to analyze the gut microbiome, SCFAs, and urolithin. There was no significant change in the gut microbial diversity in both cohorts after 4 weeks of intervention, but there was a significantly increased relative abundance of Coprococcus eutectus, Roseburia faecis, Roseburia inullnivorans, Ruminococcus bicirculans, Ruminococcus calidus, and Faecalibacterium prausnitzii. Pomegranate extract (PE) supplementation led to the augmentation of circulating propionate levels (p = 0.02) and an increasing trend for acetate levels (p = 0.12). The pomegranate extract (PE) supplementation group had an increased level of circulating urolithins compared to the placebo group (6.6% vs. 1.1%, p = 0.13). PE supplementation correlated with shifts in the gut microbiome and with higher circulating levels of propionate and acetate. Further studies should explore the implications in larger cohorts and over a longer duration.

Keywords: Pomella; ellagitannins; gut health; gut microbiome; pomegranate; punicalagin; short-chain fatty acids; urolithins.

Figure 1

CONSORT diagram schematic for the study.

Figure 2

Stool Shannon diversity at the bacterial species level was not significantly changed with PE supplementation compared to the control group at week 4. ns = not statistically significant.

Figure 3

Shifts in the gut microbiome were noted in the (A) genus, (B) species, and (C) strain levels after four weeks of PE supplementation.

Figure 4

Lefse analysis of the microbiome comparing shifts in the microbiome after 4 weeks of PE supplementation compared to placebo (control) supplementation. Results are shown for both (A) genus and (B) species. LDA effect size > 2 was considered statistically significant. There were significant increases in Coprococcus eutectus, Roseburia faecis, Roseburia inullnivorans, Ruminococcus bicirculans, Ruminococcus calidus, Faecalibacterium prausnitzii, Methanobrevibacgter smithii, and Collinsella aerofaciens.

Figure 5

LEfSe analyses of MetaCyc metabolic pathways after 4 weeks of PE or placebo supplementation from the gut microbiome. LDA effect size > 2 was considered statistically significant.

Figure 6

Plasma short-chain fatty acid levels were quantified and presented as percent change from baseline after 4 weeks of supplementation with PE or placebo. The plasma levels of (A) acetate, (B) propionate, (C) butyrate, and (D) hexanoate were analyzed. * p < 0.05.

Figure 7

Percent change from baseline of plasma urolithin A concentrations in both the PE and the placebo groups after 4 weeks of supplementation.