The concept of the “adaptogen” is historically a part of Hans Selye’s work on the physiology of stress, which he conducted from the mid-1930s. An adaptogen should provide an improvement in the body’s overall resistance in order to counteract the harmful effects of prolonged stress leading to a phase of exhaustion.
The benefits sought are a reduction of the physiological and psychological reactions to stress in the initial alarm stage (anti-alarm effect) and a delay or suppression of entry into the exhaustion stage. So, this word “stress,” so present in today’s world, what does it mean? What is the model developed by Hans Selye?
Hans Selye, the father of the concept of stress
Hans Selye, who was born in Vienna in 1907 and died in Montreal in 1982, was the founder of the Institute of Experimental Medicine and Surgery at McGill University in Montreal, which he led from 1945 to 1976.
Inventor of the theory of stress, he introduced the term in medicine in 1936, and in 1956 published a major work “The stress of life.” In his experiments on rats, Selye showed very early on that various harmful influences such as cold, heat, noise, chemical agents, etc. induce the same “non-specific” physiological response by the body (stomach and colon ulceration, immune system tissue atrophy, increased adrenal mass), which he called “stress” [Selye, 1950].
Stress is therefore a non-specific response of the body to any demand made of it, regardless of the nature of the stimulus, with identical biochemical changes, designed to confront any increased demand imposed on the human body.
This physiological response is designed to maintain what biologists call a state of equilibrium or homeostasis, meaning the constancy or stability of the body’s parameters such as body temperature, glucose level, etc. However, prolonged stress can cause psychological and physiological symptoms.
The Hans Selye model
This model, called “general adaptation syndrome”, distinguishes three stages that are compared to a normal level of resistance for the body:
A time of preparation, mobilization of resources to deal with stress (at the beginning of this stage, resistance drops below the normal level, then rises above it);
Use of resources (stage with resistance above the normal level);
Onset of various somatic disorders (decline in the level of resistance in this stage compared to the previous stage, also called “burn-out”).
If the magnitude of the stressful event does not exceed the normal response capacity, the body will not suffer any after effects. On the other hand, if the body’s resources are insufficient, and they cannot cope with the amount of stress that needs to be managed, all kinds of problems are likely to occur. The body then enters a vicious circle; the adaptation system becomes exhausted and the consequences of stress become more and more detrimental. A number of criteria determine whether or not a person has reached the stage of damage. Initially there is irritability, then insomnia, headaches, difficulty concentrating, memory problems, and so on.
The physiology of stress and adaptation
The stress response system (or non-specific adaptive response), whose function is to adapt to a situation assessed as restrictive, is designed to protect the body (defense mechanism).
Regulation of the adaptation to stress uses the “stress system” which involves:
- the nervous system (central and autonomic)
- the neuroendocrine system
- the non-specific immune system (enzymatic systems, non-specific cytokines, complement system and NK cells).
Two main mechanisms are present in the non-specific adaptive response of the stress system (nervous and neuroendocrine systems) and play an essential role in the body’s reactions to repeated stresses and in adaptation by balancing the release of adrenaline and corticosteroids (glucocorticoids):
A mechanism present in the alarm stage
involving double activation by the hypothalamus of the stress axis: peripherally, via the sympathetic autonomic nervous system and centrally, via the locus coeruleus with stimulation of the limbic and prefrontal regions;
A mechanism present in the resistance stage
involving the hypothalamic-pituitary-adrenal axis, or HPA axis, with the release of glucocorticoids (cortisol in humans).
The principal functions of catecholamines and glucocorticoids are, on the one hand, cardiovascular stimulation (increased heart rate, blood pressure and blood glucose levels) and, on the other hand, mobilization of energy sources needed for muscular effort (glycogenolysis, lipolysis) as well as an anti-inflammatory and immunosuppressive activity.
Mode of action of adaptogenic plants
The distinctive characteristic of the action of adaptogenic plants is that their protective effect in relation to stress is not the result of inhibition (antagonistic action) but that of “gentle” stimulation (agonist action) of the “stress system” (neuroendocrine and immune complex) promoting a protective effect from stress through repeated administration.
The effect of adaptogens is similar to that produced by repeated physical exercise causing a state of non-specific resistance with improved endurance in extreme conditions. They act in the body at different levels of the regulation of adaptation to stressors, activating common receptors. However, according to data from literature, the effects of adaptogenic plants are mainly associated with the endocrine mechanism involving the HPA axis. [Panossian 2003, Panossian 1999a, Panossian 1999b, Panossian 2010, Panossian 2011, Wagner 1994].
Adaptogenic plants can therefore be defined as “mild” stressors that reduce the responsiveness of the body’s defense systems and reduce the harmful effects of various aggressors due to the increase in the base level of the mediators involved in the response to stress. It is a decrease in the response of the body’s stress system.
THE EFFECTS OF ADAPTOGENIC PLANTS
The effects of adaptogens are therefore the reduction of stress reactions in the alarm stage by decreasing the sensitivity of the stress system and lengthening of the non-specific resistance stage of the stress response.
Didier Guédon, Expert on the French Pharmacopoeia Committee
Panossian A, Gabrielian E, Wagner H. On the mechanism of action of plant adaptogens with particular references on cucurbitacin R diglucoside. Phytomedicine 1999a;6:147-55.
Panossian AG, Oganessian AS, Ambartsumian M, Gabrielian ES, Wagner H, Wilkman G. Effects on heavy physical exercise and adaptogens on nitric content in human saliva. Phytomedicine 1999b;6:17-26.
Panossian AG. Adaptogens, tonic herbs for fatigue and stress. Alt Complement Ther 2003: 327-31.
Panossian A, Wikman G. Effects of adaptogens on the central nervous system and the molecular mechanisms associated with their stress—protective activity. Pharmaceuticals. 2010;3:188-224.
Panossian A, Wagner H. Adaptogens: a review of their history, biological activity and clinical benefits. HerbalGram 2011 (90):52-63.
Selye H. Stress. Acta Medical Publisher. Montreal, Quebec, Canada, 1950.
Wagner H, Nörr H, Winterhoff H. Plant adaptogens. Phytomedicine 1994;1:63-76.