Ginger on Human Health: A Comprehensive Systematic Review of 109 Randomized Controlled Trials

Clinical applications of ginger with an expectation of clinical benefits are receiving significant attention. This systematic review aims to provide a comprehensive discussion in terms of the clinical effects of ginger in all reported areas. Following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guideline, randomized controlled trials on the effects of ginger were investigated. Accordingly, 109 eligible papers were fully extracted in terms of study design, population characteristics, evaluation systems, adverse effects, and main outcomes. The reporting quality of the included studies was assessed based on the Cochrane Collaboration’s tool for assessing the risk of bias in randomized trials and integrated together with studies that investigated the same subjects. The included studies that examined the improvement of nausea and vomiting in pregnancy, inflammation, metabolic syndromes, digestive function, and colorectal cancer’s markers were consistently supported, whereas other expected functions were relatively controversial. Nevertheless, only 43 clinical trials (39.4%) met the criterion of having a ‘high quality of evidence.’ In addition to the quality assessment result, small populations and unstandardized evaluation systems were the observed shortcomings in ginger clinical trials. Further studies with adequate designs are warranted to validate the reported clinical functions of ginger.


INTRODUCTION
3 Describe the rationale for the review in the context of what is already known.

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Objectives 4 Provide an explicit statement of questions being addressed with reference to participants, interventions, comparisons, outcomes, and study design (PICOS).

METHODS
Protocol and registration 5 Indicate if a review protocol exists, if and where it can be accessed (e.g., Web address), and, if available, provide registration information including registration number.
N/A Eligibility criteria 6 Specify study characteristics (e.g., PICOS, length of follow-up) and report characteristics (e.g., years considered, language, publication status) used as criteria for eligibility, giving rationale.

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Information sources 7 Describe all information sources (e.g., databases with dates of coverage, contact with study authors to identify additional studies) in the search and date last searched.
2 Search 8 Present full electronic search strategy for at least one database, including any limits used, such that it could be repeated.
2 Study selection 9 State the process for selecting studies (i.e., screening, eligibility, included in systematic review, and, if applicable, included in the meta-analysis).
2 Data collection process 10 Describe method of data extraction from reports (e.g., piloted forms, independently, in duplicate) and any processes for obtaining and confirming data from investigators.
3 Data items 11 List and define all variables for which data were sought (e.g., PICOS, funding sources) and any assumptions and simplifications made. 3

Risk of bias in individual studies
12 Describe methods used for assessing risk of bias of individual studies (including specification of whether this was done at the study or outcome level), and how this information is to be used in any data synthesis.
N/A Summary measures 13 State the principal summary measures (e.g., risk ratio, difference in means).

N/A
Synthesis of results 14 Describe the methods of handling data and combining results of studies, if done, including measures of consistency (e.g., I 2 ) for each meta-analysis.

Section/topic # Checklist item Reported on page #
Risk of bias across studies 15 Specify any assessment of risk of bias that may affect the cumulative evidence (e.g., publication bias, selective reporting within studies).

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Additional analyses 16 Describe methods of additional analyses (e.g., sensitivity or subgroup analyses, meta-regression), if done, indicating which were pre-specified.

Study selection
17 Give numbers of studies screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally with a flow diagram.

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Study characteristics 18 For each study, present characteristics for which data were extracted (e.g., study size, PICOS, follow-up period) and provide the citations.

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Risk of bias within studies 19 Present data on risk of bias of each study and, if available, any outcome level assessment (see item 12).

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Results of individual studies 20 For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group (b) effect estimates and confidence intervals, ideally with a forest plot.

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Synthesis of results 21 Present results of each meta-analysis done, including confidence intervals and measures of consistency.

N/A
Risk of bias across studies 22 Present results of any assessment of risk of bias across studies (see Item 15).

DISCUSSION
Summary of evidence 24 Summarize the main findings including the strength of evidence for each main outcome; consider their relevance to key groups (e.g., healthcare providers, users, and policy makers).  In addition to highly emetogenic chemotherapy using ondansetron, metoclopramide, dexamethasone, 6-gingerol has reduced complete response rate significantly in both acute and delayed CINV. Serum troponin I level, chest pain (by numeric rating scale) Chest pain occurred during coronary angioplasty could be reduced by taking ginger. Also, as taking ginger is better regarding convenience and no significant complication, it could be a better choice for therapeutic agents in reducing chest pain during angioplasty. Thermal sensation and thermal comfort, oxygen consumption, CO2 production, respiratory exchange ratio, serum-free fatty acid The effect of treating ginger seems to has no effect in peripheral and central thermoregulatory function. However, treating ginger can affect fat utilization and the treating time also can affect fat utilization. Degree of nausea and vomiting, number of vomiting episodes, daily functioning related to symptoms.
It was good option for early pregnancy to take 1g of ginger in syrup or capsules daily as antiemetics. Yes Pongrojpaw et al. (2007) [24] Visual analogue nausea scores (VANS) and vomiting times Ginger showed similar effect with dimenhydrinate 3-7 days after the treatment. Therefore, taking ginger can be an alternative choice for the treatment of nausea and vomiting for pregnant women. The intraoperative incidence of nausea, the number of episodes of intraoperative nausea, the incidence of intraoperative vomiting, the number of episodes of vomiting in the first 24 h after surgery, severity of nausea postoperatively The frequency of episodes of intraoperative nausea was significantly reduced in ginger group comparing with placebo group. However, frequency of nausea, vomiting, and pain during and after an elective cesarean section was not affected by ginger.
Yes Visalyaputra et al. (1997) [30] Incidence and severity of PONV (nausea score and vomiting frequency) Incidence of PONV after gynecological laparoscopy was not reduced by taking 2 g of ginger, 1.25 mg of droperidol or both. No Incidences of nausea, vomiting, retching, sedation, abnormal movements, pain, itching and eye disturbances at the four assessment times, nausea and pain grade, postoperative use of analgesia The antiemetics effectiveness of ginger group was significantly better than placebo group, and other antiemetic groups in patients after receiving the major gynecological surgery.