Eleuthero (Eleutherococcus senticosus)

  • What it is: Often called Siberian ginseng, eleuthero is not a true ginseng. But like Panax ginseng, this popular herb is an adaptogen, meaning it is believed to enhance mental and physical performance and improve the body's resistance to environmental stressors, such as cold temperatures. Russian scientists discovered eleuthero root's beneficial properties during their 1950s search for a substitute for costly, rare P. ginseng.
  • Best for: mental endurance
  • How it works: Compounds called eleutherosides may be responsible for eleuthero's beneficial effects. In more than 1,000 scientific studies—many of them conducted in Russia—the herb has been shown to increase energy and endurance significantly for a variety of mental and physical tasks. In one study, eleuthero proved to be even more effective than Ginkgo biloba for improving cognitive function in middle age. After three months, subjects taking 625 mg of eleuthero twice daily showed significant improvements in memory, as well as feelings of well-being and levels of activity. Among those taking ginkgo (28.2 mg flavonolglycosides daily), only those older than 48 experienced enhanced memory (Journal of Neurological Sciences, 1997, vol. 150, Suppl 1).
  • Side effects: None. It is safe to take eleuthero indefinitely.

Ginseng root (Panax spp)

  • What it is: The ancient Chinese valued this slow-growing woodland plant (P. ginseng) more highly than gold. And turf wars still flare in the United States over stands of wild American ginseng (P. quinquefolium). For more than 5,000 years, people around the world have revered ginseng root as a premier herbal vitality tonic.
  • Best for: stress-related energy loss
  • How it works: Ginseng root contains compounds called ginsenosides that appear to moderate stress-related hormones, including adrenal hormones that help measure physiological stress levels. Researchers theorize that ginseng bolsters the body's resistance to stress, thus preserving and improving energy levels. In a study of 232 people suffering from long-term fatigue, researchers gave all of the participants a multi-vitamin/mineral supplement, but spiked half of the subjects' twice-daily dose with 40 mg of standardized ginseng extract. (The other half took a placebo.) After 42 days, only 5.7 percent of the ginseng group still complained of fatigue, compared to 15.2 percent of those taking the placebo (Phytotherapy Research, 1996, vol. 10, no. 1).
  • Side effects: When taken at recommended doses (check the manufacturer's label; potency varies widely), ginseng rarely causes side effects. It generally is used cyclically—for example, take the herb for one month, and then take a two-week break before resuming. If you're sensitive to stimulants, don't combine caffeine and ginseng. American ginseng (P. quinquefolium) may also decrease the effectiveness of the prescription blood-thinning drug warfarin.

Green tea (Camellia sinensis)

  • What it is: Tea—black, green, or oolong—is surpassed only by water as the most popular beverage in the world. Made from the leaves of an evergreen shrub native to Asia, green tea is minimally processed (the leaves are simply dried, while black and oolong tea leaves are fermented).
  • Best for: immediate boost
  • How it works: A powerful nervous-system stimulant, caffeine temporarily enhances mental and physical performance. At about 30 mg of caffeine per cup, green tea delivers less caffeine than coffee (100 to 150 mg per cup) or black tea (40 to 60 mg per cup). Therefore, many people who can't tolerate higher caffeine content do fine with green tea. Tea also contains L-theanine, a rare amino acid that signals the brain to increase alertness while, paradoxically, also eliciting a sense of tranquility. Green tea boasts dozens of additional health-promoting benefits. It's a powerful antioxidant; protects against heart disease, cancer, and diabetes; and even helps to burn fat.
  • Side effects: Green tea, like any caffeinated beverage, can cause nervousness, insomnia, irritability, and headaches in people who are sensitive to caffeine.

Herbalist and author Laurel Vukovic has published nine books, including Herbal Healing Secrets for Women (Prentice Hall, 2000).