The influence of hydrastis canadensis on the gastrointestinal microbiota – beneficial or detrimental effects? : a critical review to update naturopathic and western herbal clinical practice

Hydrastis canadensis (H. canadensis) is utilised in naturopathy and herbal medicine as an antimicrobial agent and vulnerary and is considered to have strong actions against pathogenic microorganisms. Traditional Western herbal practice suggests that Hydrastis should only be utilised as a short-term treatment due to the potential for it to have negative impacts on the microbiota of the gastrointestinal tract (GIT). This research piece will critically appraise the recent clinical trial evidence on this topic and evaluate whether H. canadensis is detrimental or beneficial to the gut microbiome. A PubMed and Google Scholar search sought studies on the microbiome effects of H. canadensis and its constituents. Quality was assessed using CASP instruments. Articles related to the research question were purposely sought and included in a narrative, critical synthesis. Research assessing the impact of H. canadensis as a herbal preparation on the human GIT ecosystem is scant; however, evidence for one of its constituents, berberine, is emerging. Clinical benefit from berberine administration have been observed for people with diabetes, diabetes-related cardiovascular risk factors and for people with Graves’ disease when taken from periods between 1 week to 6 months. However, clinical improvements were associated with negative shifts in the gastrointestinal ecosystem that could have detrimental impacts over longer periods, including increasing the risk of chronic diseases, including the increased risk of colon cancer. Few non-serious adverse events were reported for berberine, these were mostly gastrointestinal in nature. The evidence is limited in volume and more clinical investigations are needed, particularly examining the effects of whole preparations of H. canadensis in humans, as no studies evaluated the herbal extract as it is prescribed in naturopathic and Western herbal medicine practice.