Cranberry Extract & the Microbiota

Results of a small human clinical trial recently published in NPJ Biofilms and Microbiomes indicate that short-term use of cranberry extract has a bifidogenic effect and increases the abundance of butyrate-producing bacteria, the first study to report on cranberry-induced microbiome changes. This study was done both to characterize the specific polyphenols and oligosaccharides found within a specific cranberry extract, and to determine its effects on the microbiome (using 16 S rRNA sequencing) of 39 healthy volunteers after only 4 days of use.

The majority of the polyphenols in this cranberry extract were found to be flavan-3-ols (75% of total), with lesser amounts of anthocyanidins (5%), flavonols (13%), and phenolic acids (7%). Acid hydrolysis was used to break down larger oligosaccharides into simple carbohydrates, which included glucose, arabinose, xylose, and others (no detail was provided for the type of oligosaccharides found prior to hydrolysis, but arabinoxyloglucans plausibly account for the majority).

Among the 28 participants who provided fecal samples at baseline and after 4 days of use (1 capsule twice per day), the extract was shown to significantly increase species richness and decrease α-diversity. Specifically, it reduced the abundance of Bacteroides (including 5 Bacteroides species) while increasing the abundance of two species of Bifidobacterium (Bifidobacterium adolescentis and Bifidobacterium longum). Previous research in experimental models suggests that cranberry extract may also increase Akkermansia muciniphila levels, but overall no changes were reported in this study, potentially due to the short time frame or limitations in the accurate measurement of Akkermansia growth. Additionally, both plasma and fecal samples indicated trends toward favorable short-chain fatty acid production, including relative increases in butyrate and propionate (plasma only), and a reduction in acetate levels. Larger studies of longer duration would help to flush out these changes, and possibly identify variability in response to supplementation.