Although ginger is used in many forms, including fresh ginger used in cooking or chai (Indian spicy tea), pickled or glazed ginger, ethanol extracts and concentrated powdered extracts, preparations made with the root are used medicinally. Depending on the specific solvent used, the resultant preparation will contain different concentrations of the active constituents and may differ markedly from crude ginger. Although the great majority of research refers specifically to the species Zingiber officinale, there is the potential for confusion with other species or even with other genera. Furthermore, there are reported to be wide variations in the quality of commercial ginger supplements with concentrations of gingerols ranging from 0.0 to 9.43 mg/g. As such, the results of specific research can not necessarily be extrapolated to different preparations.
PREVENTION OF NAUSEA AND VOMITING
Many clinical studies have investigated the effects of ginger in the prevention and treatment of nausea and vomiting associated with different circumstances, including pregnancy, the postoperative period, motion sickness and chemotherapy.
A recent systematic review of 24 RCTs covering 1073 patients suggest that results for the treatment of nausea and vomiting in pregnancy are encouraging; however, results for postoperative nausea and vomiting and motion sickness are unclear and daily doses of up to 6 g of ginger seems to have few side-effects. More recent reviews provide further encouragement and suggest that ginger may indeed be effective in nausea associated with pregnancy and the postoperative period.
Clinical note — Morning sickness
Nausea and vomiting are the most common symptoms experienced in early pregnancy, with nausea affecting between 70% and 85% of women. About half of pregnant women experiencevomiting. Hyperemesis gravidarum is more severe and affects between 0.3% and 2% of all pregnant women. It is a multifactorial disease in which pregnancy-induced hormonal changes associated with concurrent gastrointestinal dysmotility and possible Helicobacter pylori infection function as contributing factors.
Nausea of pregnancy
There are many studies, including an observational study and at least six RCTs, as well as multiple systematic reviews, including a Cochrane review, that suggest that ginger powder or extract may be safe and effective in treating nausea and vomiting of pregnancy. The most recent review, which considers six double-blind RCTs with a total of 675 participants, and a prospective observational cohort study of 187 women, suggest that ginger is superior to placebo and as effective as vitamin B6 in relieving pregnancy-related nausea and vomiting and that there is an absence of significant side-effects and adverse pregnancy outcomes.
In three double-blind, placebo-controlled, randomised trials of ginger for pregnancy related-nausea and vomiting, including one trial on hyperemesis gravidarum, 1 g ginger in divided doses was significantly more effective than placebo in reducing nausea and vomiting. In a further double blind of 120 women, 25 mg of the ginger extract EV.EXT35 (equivalent to 1.5 g of dried ginger) four times daily was useful in patients experiencing nausea and retching, although no significant result was seen for vomiting.
In two further randomised, double-blind, controlled trials, one involving 138 women and the second 291 women, 1-1.5 g of ginger was found to be equivalent to vitamin B6 in helping to reduce pregnancy-related nausea, dry retching, and vomiting.
Postoperative nausea Ginger may be useful for the prevention of postoperative nausea; however, not all studies have produced positive results and as the ginger preparations used have not been standardised, it is difficult to directly compare studies. A recent meta-analysis of five randomised trials, however, including a total of 363 patients found that a fixed dose of at least 1 g of ginger was more effective than placebo for the prevention of postoperative nausea and vomiting.
Most of the studies on postoperative nausea and vomiting have been done on patients undergoing gynaecological surgery. In two such randomised, placebo-controlled, double-blind studies, ginger significantly reduced the incidence of postoperative nausea and vomiting, although two further studies failed to show any benefit with ginger. A fifth study of 80 women undergoing gynaecological laparoscopy found that 1 g of ginger taken 1 hour before surgery was significantly superior to placebo in reducing the incidence of nausea 2-4 hours afterwards; however, it failed to show statistical significance for an observed reduction in the incidence and frequency of vomiting.
Although other types of surgery have not been as extensively studied as gynaecological surgery, there is a report on 6 months of clinical anaesthetic experience that suggests that a nasocutaneously administered 5% solution of essential oil of ginger given pre-operatively, together with conventional therapies, to general anaesthesia patients at high risk for postoperative nausea and vomiting is a safe and cost-effective way of reducing nausea and vomiting post anaesthesia.
In the only double-blind, placebo-controlled study of postoperative nausea and vomiting in patients undergoing middle ear surgery, ginger was ineffective and the use of 1 g of ginger 1 hour before surgery was associated with significantly more postoperative nausea and vomiting than the use of ondansetron or placebo.
Commission E approves the use of ginger root for the prevention of motion sickness and several clinical studies have assessed its effects as either prophylaxis or treatment. An early double-blind, randomised, placebo-controlled study involving 80 naval cadets found that ginger was significantly superior to placebo in reducing symptoms of vomiting and cold sweats due to seasickness. Fewer symptoms of nausea and vertigo were also reported with ginger, but the difference was not statistically significant. In another randomised double-blind study of seasickness involving over 1700 tourists on a whale-watching safari 300 km north of the Arctic circle, 500 mg ginger was found to be as effective for the treatment of motion sickness as several common anti-emetic medications (cinnarizine, cyclizine, dimenhydrinate, domperidone, meclizine and scopolamine) with ginger preventing seasickness in 80% of the subjects during the 6-hour boat trip, although the incidence of severe vomiting did not differ significantly between treatment groups.
At least three studies have had mixed results from experimental models of motion sickness whereby subjects are seated in a rotating chair. The first study involving 28 volunteers found no significant protective effects for powdered ginger (500 mg or 1000 mg) or fresh ginger root (1000 mg), whereas a second study involving 36 undergraduate men and women who reported very high susceptibility to motion sickness found that ginger was superior to dimenhydrinate. More recently, another double-blind, randomised, placebo-controlled crossover study showed positive benefits with ginger pretreatment on prolonging time before nausea, shortening recovery time and effectively reducing nausea. This study used pretreatment doses of 1000 mg and 2000 mg, which were also shown to reduce tachygastria and plasma vasopressin.
In an open study, 1.5 g ginger was found to decrease psoralen-induced nausea in 11 patients treated with photopheresis for cutaneous T-cell lymphoma.
Powdered ginger root effectively reduced cyclophosphamide-induced nausea and vomiting in a randomised, prospective, crossover double-blind study, with the anti-emetic effect of ginger being equal to metoclopramide. Ginger was found to have similar efficacy to metoclopramide in reducing cisplatin-induced emesis in a randomised, double-blinded, crossover study of 48 gynaecologic cancer patients receiving chemotherapy.
Ginger is described in Ayurvedic (traditional Indian) and Tibb (traditional Arabian) systems of medicine to be useful in inflammation and rheumatism and this traditional use is supported by modern studies demonstrating ginger’s anti-inflammatory activity.
A randomised, double-blind, placebo-controlled, multicentre, parallel-group 6-week study of 261 patients found that a highly purified and standardised ginger extract (EV.EXT 77) moderately reduced the symptoms of OA of the knee. Similarly, 250 mg of the ginger extract (Zintona EC) four times daily for 6 months was shown to be significantly more effective than placebo in reducing pain and disability in 29 OA patients in a double-blind, placebo-controlled, crossover study.
These studies are supported by an open retrospective study involving 56 patients (28 with RA, 18 with OA, 10 with muscular discomfort) that revealed that more than three-quarters experienced varying degrees of relief of pain and swelling from the long-term use of powdered ginger. Further support comes from studies comparing ginger to NSAIDs.
In one double-blind, randomised, placebo-controlled trial involving 120 patients, 30 mg of an ethanolic ginger extract equivalent to 1 g of ginger and prepared from fresh ginger purchased from a local market in India was found to be significantly more effective than placebo and was as effective as 1.2 g of ibuprofen in the symptomatic treatment of OA. In another double-blind crossover study 170 mg of the ginger extract EV.ext-33 with a standardised content of hydroxy-methoxy-phenyl compounds given twice daily was found to be significantly more effective than placebo but not as effective as ibuprofen in reducing pain and disability in 75 patients with OA before the crossover period, whereas no statistical difference was seen between ginger and placebo in the analysis after the crossover period. The authors commented that the washout period may have been insufficient and that ginger might need to be administered for longer than 3 weeks, and possibly in a higher dosage, to be clinically effective.
Ginger stimulates the flow of saliva, bile and gastric secretions and therefore is traditionally used to stimulate appetite, reduce flatulence and colic, gastrointestinal spasms and generally act as a digestive aid. Commission E approves the use of ginger root for the treatment of dyspepsia.
Ginger is used to prevent and treat migraine headache. Its ability to inhibit thromboxane A2 and exert antihistamine, anti-inflammatory and gastric actions makes it a theoretically attractive choice. This use is supported by an open-label study of 30 migraine sufferers that reported that treatment with a sublingual ginger and feverfew preparation (GelStat MigraineO) in the initial phase of a migraine resulted in most patients being satisfied with the therapy and being pain-free or only having mild headache post-treatment.