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Rhodiola rosea has been intensively studied in Russia and Scandinavia for more than 35 years. Although the majority of this research on Rhodiola rosea is unavailable for review, available literature is supportive of its adaptogenic properties. Similar to other plant adaptogens investigated by Russian researchers, such as Eleutherococcus senticosus (Siberian ginseng) and Panax ginseng (Korean ginseng), extracts of this plant produce favorable changes in a variety of diverse areas of physiological function, including neurotransmitter levels, central nervous system activity, and cardiovascular function.
Rhodiola rosea has been categorized as an adaptogen by Russian researchers due to its observed ability to increase resistance to a variety of chemical, biological, and physical stressors. Origination of the term adaptogen has been dated to 1947 and credited to a Russian scientist, Lazarev. He defined an "adaptogen" as an agent that allows an organism to counteract adverse physical, chemical, or biological stressors by generating non-specific resistance. Inherent in his definition is the concept that administration of the adaptogenic agent allows an organism to pre-adapt itself in a manner that allows it to be more capable of responding appropriately when diverse demands are eventually placed on it. In 1969, Brekhman and Dardymov proposed specific criteria that need to be fulfilled in order for a substance to qualify as an adaptogen.
Subjecting animals and humans to a period of stress produces characteristic changes in several hormones and parameters associated with the central nervous system and the hypothalamic-pituitary-adrenal axis (HPA). HPA changes include an increase in cortisol, a reduced sensitivity of the HPA to feedback down-regulation, and a disruption in the circadian rhythm of cortisol secretion. Central nervous system changes include the stress-induced depletion of catecholamine neurotransmitters such as norepinephrine and dopamine. An acute increase in beta-endorphin levels is also observed under stressful conditions.
To successfully combat stress and stressful situations, adaptation is required. Adaptation might be best thought of as the ability to be exposed to a stressor, while responding with either decreased or no characteristic hormonal perturbations. Adaptation also implies being prepared to and capable of rapidly reassuming homeostasis after the stressor is withdrawn. As an example, a well-trained athlete can participate in an event that would induce a large HPA perturbation (stress response) in a sedentary person, and yet the athlete will be relatively unaffected. This is a result of adaptation that has occurred during the athlete's training process. Additionally, if athletes are exposed to stressors they were not trained for, hormonal perturbations characteristic of a stress response would be expected: however, this response might not be as great as that found in less fit individuals. Furthermore, after the stress ended, their physiology would be expected to re-establish homeostasis rapidly. This is a result of non-specific resistance to stress gained by virtue of a training-induced higher level of fitness.
The utility of plant adaptogens is analogous to the training an athlete undergoes in order to prepare for competition. Plant adaptogens cause our physiology to begin the adaptation process to stress. When a stressful situation occurs, consuming adaptogens generates a degree of generalized adaptation (or non-specific resistance) that allows our physiology to handle the stressful situation in a more resourceful manner.
As an example of this process, Rhodiola rosea administration promotes a moderate increase in the amount of serum immunoreactive beta-endorphin in rats under basal conditions. This moderate increase is similar to that found when rats are adapted to exercise. When Rhodiola rosea-treated rats were subjected to a 4-hour period of non-specific stress, the expected elevation in beta-endorphin was either not observed or substantially decreased. Consequently, the characteristic perturbations of the HPA were decreased or totally prevented.3 In these rats administration of Rhodiola rosea appears to have generated non-specific resistance and prepared the rats to respond more appropriately to the eventual stressful situation.
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