Despite compositional alterations in gastrointestinal microbiota being purported to underpin some of the therapeutic effects of ginger, the effect of a standardized ginger supplement on gut microbiota has not been tested in humans.
To determine the effect of a standardized ginger (Zingiber officinale) root powder, compared to placebo, on gastrointestinal bacteria and associated outcomes in healthy adults.
A randomized double-blind placebo-controlled trial allocated participants aged 18-30-years to ginger or microcrystalline cellulose (MCC) placebo. The intervention comprised 1.2g/day of ginger (four capsules per day totaling 84mg/day of active gingerols/shogaols) for 14-days following a 1-week run-in period. Primary outcomes were gastrointestinal community composition, alpha and beta diversity, and differential abundance, measured using 16S rRNA gene sequencing of fecal samples. Secondary outcomes were gastrointestinal symptoms, bowel function, depression, anxiety, stress, fatigue, quality of life, and adverse events.
n=51 participants were enrolled and analyzed (71% female; mean age 25 [SD: 3] years; ginger: n=29, placebo: n=22). There was a greater increase in relative abundance of phylum, Actinobacteria, observed following ginger supplementation compared to placebo (U: 145.0; Z: -2.1; p=0.033). Ginger was associated with a greater abundance of the genera Parabacteroides, Bacillus, Ruminococcaceae incertae sedis, unclassified Bacilli, families Defluviitaleaceae, Morganellaceae, and Bacillaceae as well as lower abundance of the genus Blautia and family Sphingomonadaceae (p<0.05). An improvement in indigestion symptoms was observed with ginger supplementation (U:196.0; Z:-2.4; p=0.015). No differences between ginger and placebo groups were found for alpha and beta diversity nor other secondary outcomes. No moderate or severe adverse events were reported.
Supplementation with ginger root powder was safe and altered aspects of the gastrointestinal bacteria composition; however, did not change alpha- or beta-diversity, bowel function, gastrointestinal symptoms, mood, or quality of life in healthy adults. These results provide further understanding regarding the mechanisms of action of ginger supplementation.
Australia New Zealand Clinical Trials Registry (reference: ACTRN12620000302954p; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=379178&isReview=true) and the Therapeutic Goods Administration (reference: CT-2020-CTN-00380-1).

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