Orally consumed ginger and human health: an umbrella review

BACKGROUND: Emerging evidence supports the health benefits of ginger for a range of conditions and symptoms; however, there is a lack of synthesis of literature to determine which health indications are supported by quality evidence. OBJECTIVES: In this umbrella review of systematic reviews we aimed to determine the therapeutic effects and safety of any type of ginger from the Zingiber family administered in oral form compared with any comparator or baseline measures on any health and well-being outcome in humans. METHODS: Five databases were searched from inception to April 2021. Review selection and quality were assessed in duplicate using the Assessment of Multiple Systematic Reviews–2 (AMSTAR-2) checklist and the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) method, with results presented in narrative form. RESULTS: Twenty-four systematic reviews were included with 3% overlap of primary studies. The strongest evidence was found for the antiemetic effects of ginger in pregnant women (effect size: large; GRADE: high), analgesic effects for osteoarthritis (effect size: small; GRADE: high), and glycemic control (effect size: none to very large; GRADE: very low to moderate). Ginger also had a statistically significant positive effect on blood pressure, weight management, dysmenorrhea, postoperative nausea, and chemotherapy-induced vomiting (effect size: moderate to large; GRADE: low to moderate) as well as blood lipid profile (effect size: small; GRADE: very low) and anti-inflammatory and antioxidant biomarkers (effect size: unclear; GRADE: very low to moderate). There was substantial heterogeneity and poor reporting of interventions; however, dosage of 0.5–3 g/d in capsule form administered for up to 3 mo was consistently reported as effective. CONCLUSIONS: Dietary consumption of ginger appears safe and may exert beneficial effects on human health and well-being, with greatest confidence in antiemetic effects in pregnant women, analgesic effects in osteoarthritis, and glycemic control. Future randomized controlled and dose-dependent trials with adequate sample sizes and standardized ginger products are warranted to better inform and standardize routine clinical prescription.