Ginseng has been used in Chinese medicine to promote health for 2,000 years. A National Cancer Institute survey in 2004 found that 36% of adults use ginseng or some other form of complementary or alternative medicine. But scientists have never before studied ginseng's potential to ease cancer fatigue in such a carefully controlled way, says lead author Debra Barton of the Mayo Clinic in Minnesota.

Barton's research is one of a trio of studies, all financed by the cancer institute, on complementary and alternative cancer medicines presented Sunday at the American Society of Clinical Oncology meeting in Chicago. The studies are part of a growing effort to bring scientific scrutiny to popular folk remedies and natural products.

In Barton's pilot study of 282 patients, researchers randomly assigned patients to take either a placebo or one of three daily doses of ginseng: 750 milligrams, 1,000 milligrams or 2,000 milligrams.

After eight weeks, roughly 27% of those who took the two highest ginseng doses rated their fatigue as "moderately" or "very much" better, she says. Only 10% of those who took placebos or the lowest ginseng dose improved that much. One-third of those on the highest two doses were satisfied with treatment, compared with 24% of those on low-dose ginseng and 13% of those on placebos. Ginseng didn't appear to cause any side effects, Barton says. The study didn't address whether ginseng controlled patients' cancer.

Moriarty, who later learned that she had been given the lowest ginseng dose, says the capsules helped keep her focused in the afternoon. She has opted to continue using the plant. "I've never experienced anything quite like this," Moriarty says. "It clears your head."

The design of Barton's study — considered the gold standard of medical evidence — makes its results reliable, says Andrea Barsevick, director of nursing research at Fox Chase Cancer Center in Philadelphia. Although researchers have produced at least 20 previous studies of ginseng and cancer, Barsevick says, all were small, lacked comparison groups or had other problems that made them less reliable.

Barsevick notes that cancer patients and survivors desperately need a better way to treat fatigue, which affects most of those getting chemo and up to 35% of patients who finish treatment. The only proven way to relieve cancer-related fatigue, she says, is exercise.

Yet Barton says she can't yet recommend that cancer patients start taking ginseng. Researchers need to confirm the results in a larger study. Barton notes commercial ginseng may not provide the same benefit found in the study. Because plants such as ginseng are sold as nutritional supplements, they aren't regulated as drugs, Barton says. That means that some ginseng pills may contain higher doses than others. Scientists who have analyzed a variety of herbal supplements have found that ingredients listed on the label may be different from those found in the product, she says.

Ginseng tea also may not be as effective as the ginseng capsules given to study patients, Barton says. Her study used American ginseng, known scientifically as Panax quinquefolius and sometimes marketed as Canadian, Wisconsin or North American ginseng. The ginseng was extracted from the roots of plants grown by a farmer in Wisconsin. A lab confirmed its content and quality.