Rhodiola is also called Golden root. It is native to Eastern Europe, Russia, China, Serbia and the Ukraine. Traditional healers believed that Rhodiola could prolong life by increasing vitality, decrease fatigue, and increase resistance to stress.
The main constituents in Rhodiola are antioxidants, flavonoids, and many compounds that lend its adaptogen properties; of which the most well known is rosavin. Rosavin is the compound that is used for standardization of Rhodiola supplements. 
Rhodiola is believed to exert its affects via modulation of the neurotransmitters in the central nervous system. Rhodiola has been shown to affect levels of dopamine, serotonin, and norepinephrine. It also has action in the periphery on catecholamine and steroid hormone metabolism via cortisol and DHEA.
Rhodiola is considered by many to be an effective anti-oxidant, anti-fatigue agent, and nervous system tonic. Again, Rhodiola is an adaptogen and effects levels of neurotransmitters and other cell signaling molecules in the body. It is believed to be helpful in cases of depression, cancer, chronic fatigue, and altitude sickness. However, much of the research conducted on Rhodiola has been done in Eastern Europe and Russia and has not been translated.
The rhizome or root is the medicinal part of Rhodiola.
Rhodiola may improve exercise performance and endurance. In one particular study, it was shown to increase the capacity of exercise, as well as increase the time to exhaustion. Rhodiola also had a positive affect on lung ventilation. 
Rhodiola can be used in acute situations of increased stress, decreasing fatigue and improving the capacity to accomplish both physical and cognitive tasks. [3, 4]
Rhodiola is also purported to be a powerful antioxidant. By nourishing the “Qi,” as documented in Traditional Chinese Medicine, Rhodiola may be useful for prolonging age. 
Rhodiola has proven to improve learning and memory in animal models. Al though anecdotal and evidence from differing case studies support this theory, human trials are still needed to confirm this information. 
Rhodiola can be used for acute and chronic situations, with different dosage levels. Rhodiola should not be used long term without a discontinuance period. The recommendation is similar to other adaptogen herbs like Panax ginseng and Siberian ginseng; take for one month, then take a week off, and then begin again.
The recommended dose for an acute situation is 1000 - 1800 milligrams (mg) per day of an extract standardized to 1% rosavin, or 550 - 900mg of an extract standardized to 2% rosavin. For long term or chronic use, the recommended dose is 3 times less than the acute: 360 - 600mg of 1% and 180 - 300mg of 2% rosavin.
Side effects of too high a dose or chronic administration include irritability and insomnia. This usually appears when doses in excess of 1.5 - 2.0 grams of a 2% extract are regularly administered.
There are no contraindications to the use of Rhodiola. However, women who are pregnant or nursing should consult with their physician prior to beginning treatment with Rhodiola, due to the lack of clinical information in these particular populations.
1. Monograph: Rhodiola rosea. Altern Med Rev. 2002; 7(5): 421-423.
2. DeBock K et al. Acute Rhodiola intake can improve endurance exercise performance. Int J Sport Nutr Exerc Metab. 2004 Jun; 14(3): 298-307.
3. Shevtsov VA et al. A randomized trial of two different doses of SHR-5 Rhodiola rosea extract verses placebo and control of capacity for mental work. Phytomedicine. 2003 Mar; 10(2-3): 95-105.
4. Darbinyan V et al. Rhodiola rosea in stress induced fatigue: a double blind crossover study of a standardized extract SHR-5 with repeated low dose regimen on the mental performance of healthy physicians during night duty. Phytomedicine. 2000 Oct; 7(5): 365-371.
5. Ohsugi M et al. Acute oxygen scavenging activity of traditional nourishing tonic herbal medicines. J Ethnopharmacol. 1999 Oct; 67(1): 111-119.
6. Petkov VD et al. Effects of alcohol aqueous extract from Rhodiola rosea L. roots on learning and memory. Acta Physiolpharmacol Bulg. 1986; 12(1): 3-16.