Rhodiola comprises more than 200 related species of plants in the Crassulacea family and is generally found in the arctic mountain regions of Siberia (Kelly, 2001). Of the many species of rhodiola, only two have been studied at any appreciable level in humans: Rhodiola rosea and Rhodiola crenulalci ("Rhodiola rosea," 2002) The root of the plant is used medicinally and is also known as arctic root, golden root (for rosea), and more recently, crenulin (for crenulata). Rhodiola has been used for centuries to increase the body's resistance to physical and mental stresses (Zhang et al., 1989), As a modern-day dietary supplement, rhodiola is typically promoted for boosting energy levels, relieving stress and anxiety, and enhancing athletic performance.
Rhodioln rosea extract appears to be valuable as an adaptogen, increasing the body's ability to deal with a number of psychological and physiological stresses. Of particular value is the theoretical role of rhodiola in increasing the body's ability to take up and use oxygen, an effect similar to that of cordyceps, which may explain some of the nonstimulant "energizing" effects attributed to the plant. Rhodiola is often called the "poor man's" cordyceps based on ancient stories in which "commoners" used rhodioia for energy because the plants grew wild throughout the Rhodiola is typically considered an adaptogen (like ginseng) and is believed to invigorate the body and mind to increase resistance to a multitude of stresses. The key active constituents in rhodiola are believed to be rosavin, rosarin, rosin, and salidroside (Kelly, 2001), which are reported in animal studies to influence levels of neurotransmitters (serotonin, dopamine, and norepinephrine), catecholamines, and free radicals (Maslova et al., 1994; Ohsugi et al., 1999; Rege et al., 1999)
Unfortunately, most of what we know about the clinical effects of rhodiola supplementation comes from a handful of small studies in which standardized extracts of both Rhodiola rosea and Rhodiola crenulata have been shown to increase cognitive function and mental concentration while reducing feelings of general fatigue (Darbinyan et al., 2000, Spasov et al., 2000a, 2000b). One of the theoretical mechanisms of action for rhodiola's antifatigue effects is an enhancement of oxygen efficiency; although some studies have observed this effect (Ha et al., 2002), other studies have not (Wing et al., 2003). A possible reason for the discrepancy in these results is study design, with positive-effect studies tending to have larger numbers of subjects, longer durations of supplementation, and more complete characterizations of study materials (standardized Rhodiola extracts).
For example, one study of rhodiola followed 15 subjects supplemented with rhodiola for 7 days under simulated high-altitude conditions (4,600 meters) and found a reduction in hypoxia-induced oxidative stress but no change in hemoglobin saturation or blood oxygen levels (Wing et al., 2003). In contrast, a similar study (Ha et al., 2002) of 24 subjects living at a higher altitude (5,380 meters) for a longer duration (1 year) showed a beneficial effect of rhodiola supplementation on blood oxygen levels when rhodiola was given over a longer period (24 days).
Another significant factor among the handful of clinical studies on rhodiola is the material being studied, with well-characterized extracts (standardized to salidroside, rosavin, and other active/marker compounds) showing significant beneficial effects, while less well-characterized material (non-standardized extracts and raw rhodiola root) tending to show modest or no beneficial effects. For example, three well-controlled studies of a standardized extract of Rhodiola rosea have shown benefits in reducing mental and physical fatigue in physicians working night duty (Darbinyan et al., 2000) and students under stress (Spasov et al., 2000a, 2000b).
Rhodiola rosea extract is thought to be quite safe. There are no known contraindications or interactions with other drugs or herbs, but there are anecdotal reports of mild allergic reactions (rashes) in some persons.
General dosage recommendations for extracts of both Rhodiola rosea and Rhodiola crenulata are typically in the range of 100-600 mg/day. Ideally, a standardized Rhodiola extract is preferred, with the best efficacy demonstrated for extracts with active/marker compounds in the ranges of 3-6% rosavin and 1-2% salidroside (Kelly, 2001).