Native to southern Asia, ginger is a 2- to 4-foot-long perennial that produces grass-like leaves up to a foot long and almost an inch wide. Although it is called ginger root in the grocery store, the part of the herb used is actually the rhizome, the underground stem of the plant, with its bark-like outer covering scraped off.

Ginger has been used as food and medicine for millennia. Arabian traders carried ginger root from China and India to be used as a food spice in ancient Greece and Rome, and tax records from the second century AD show that ginger was a delightful source of revenue to the Roman treasury.

Chinese medical texts from the fourth century BC suggest that ginger is effective in treating nausea, diarrhea, stomachaches, cholera, toothaches, bleeding, and rheumatism. Ginger was later used by Chinese herbalists to treat a variety of respiratory conditions, including coughs and the early stages of colds.

Ginger's modern use dates back to the early 1980s, when a scientist named D. Mowrey noticed that ginger-filled capsules reduced his nausea during an episode of flu. Inspired by this, he performed the first double-blind study of ginger. Germany's Commission E subsequently approved ginger as a treatment for indigestion and motion sickness.

One of the most prevalent ingredients in fresh ginger is the pungent substance gingerol. However, when ginger is dried and stored, its gingerol rapidly converts to the substances shogaol and zingerone. If any of these substances has medicinal effects remains unknown.

Some evidence suggests that ginger may be at least slightly helpful for the prevention and treatment of various forms of nausea, including motion sickness, the nausea and vomiting of pregnancy (morning sickness), and postsurgical nausea.

Note: If you are pregnant or undergoing surgery, do not self-treat with ginger except under physician supervision.

Scant preliminary evidence suggests that ginger might be helpful for osteoarthritis. And, one small study suggests it may beneficial forhigh cholesterol.43

Ginger has been suggested as a treatment for numerous other conditions, including atherosclerosis, migraine headaches, rheumatoid arthritis, ulcers, depression, and impotence. However, there is negligible evidence for these uses.

In traditional Chinese medicine, hot ginger tea taken at the first sign of a cold is believed to offer the possibility of averting the infection. However, once more, there is no scientific evidence for this use.