Hormesis is any process in a cell or organism that exhibits a biphasic response to exposure to increasing amounts of a substance or condition. Within the hormetic zone, there is generally a favorable biological response to low exposures to toxins and other stressors. Hormesis comes from Greek hórmēsis “rapid motion, eagerness”, itself from ancient Greek hormáein “to set in motion, impel, urge on”. Hormetics is the term proposed for the study and science of hormesis.
Since the basic survival capacity of any biological system depends on its homeostatic ability, biogerontologists proposed that exposing cells and organisms to mild stress should result in the adaptive or hormetic response with various biological benefits. This idea has now gathered a large body of supportive evidence showing that repetitive mild stress exposure has anti-aging effects. Exercise is a paradigm for hormesis in this respect.
Some of the mild stresses used for such studies on the application of hormesis in aging research and interventions are heat shock, irradiation, prooxidants, hypergravity, and food restriction.
Some other natural and synthetic molecules, such as celastrols from medicinal herbs and curcumin from the spice turmeric have also been found to have hormetic beneficial effects. Such compounds which bring about their health beneficial effects by stimulating or by modulating stress response pathways in cells have been termed “hormetins”. Hormetic interventions have also been proposed at the clinical level, with a variety of stimuli, challenges and stressful actions, that aim to increase the dynamical complexity of the biological systems in humans.