Ginger is a perennial plant with a leafy stem reaching approximately a meter in height. The plant has green, grass-like leaves, which are 15 to 30 centimeters long and roughly 2 centimeters in width. Cultivated ginger is propagated by planting root cuttings, and rarely flowers or goes to seed. Wild ginger produces small, yellow-green flowers enclosed in overlapping green bracts, which are situated in dense, conical spikes, from 5 to 7 centimeters long. Beneath the ground, ginger has a thick, pungent rhizome (commonly called ginger root), which is used as a spice, as a food, and for health purposes.
The primary chemical constituents of ginger include essential oils (zingiberine, bisabolene, camphene, alpha-pinene, cineol, beta-phellandrene, and myrcene) and pungent principles (gingerol, zingerone, and shogaol). Concentrations of these components may vary, depending on growing conditions and country of origin.
Most of the research on ginger has focused on its potential as an antinauseant and digestive tonic. Germany's Commission E (the German government's expert committee on herbal remedies) has approved the use of ginger for prevention of motion sickness and treatment of indigestion. Some studies indicate that ginger may help control nausea caused by surgery, motion sickness, and pregnancy. However, in two studies on post-operative nausea, ginger was found to be no more effective than placebo. Further research may help resolve this conflicting data. Japanese scientists have isolated compounds in ginger that appear to have anti-ulcer effects; however, the efficacy of ginger for preventing or treating ulcers in humans has not been demonstrated.
The Commission E Monographs recommend a daily dosage of 2 to 4 grams of fresh dried rhizome, and there are no known side effects at this dosage range. Extremely high doses (more than 6 grams of dried rhizome or its equivalent per day) may cause gastrointestinal discomfort. Ginger has no known toxicity.