Adaptogens Explained: Definition, History, and How They Work on the HPA Axis

London, United Kingdom — 31 March 2026

The term "adaptogen" has become ubiquitous across the supplement industry, yet its scientific lineage stretches back more than seven decades. Understanding what adaptogens actually are — and how they differ from conventional stimulants and sedatives — is essential for any B2B buyer evaluating formulation strategies or marketing claims.

What Is an Adaptogen?

An adaptogen is a natural substance — typically a plant extract or mushroom — that helps the body resist and adapt to physical, chemical, and biological stressors. The concept was first formalised in 1947 by Soviet toxicologist Dr Nikolai Lazarev, who defined adaptogens as agents that increase "non-specific resistance" to stress without causing significant side effects. His student, Dr Israel Brekhman, later refined the criteria: an adaptogen must be non-toxic at normal doses, produce a non-specific defensive response, and exert a normalising (balancing) effect on physiology regardless of the direction of the imbalance.

A Brief History of the Term

Soviet military and athletic programmes drove early adaptogen research throughout the 1950s and 1960s, primarily investigating Siberian ginseng (Eleutherococcus senticosus) for endurance and recovery. Western science largely ignored these findings until the 1990s, when the European Medicines Agency began reviewing traditional herbal monographs. By the 2010s, adaptogens had migrated from niche herbalism into mainstream supplement marketing, with the global adaptogen market reaching an estimated $12.4 billion in 2025. The regulatory landscape remains fragmented: the EU permits certain traditional-use claims, while the US FDA has not formally recognised the adaptogen category.

How Adaptogens Differ from Stimulants and Sedatives

Stimulants such as caffeine trigger a sharp spike in cortisol and catecholamines, producing alertness at the cost of eventual energy crashes and tolerance. Sedatives like valerian suppress central nervous system activity, inducing calm but potentially impairing cognitive function. Adaptogens occupy a fundamentally different pharmacological niche: they modulate the stress response bidirectionally. In a fatigued individual, an adaptogen may upregulate energy pathways; in an overstimulated individual, the same compound may promote calm. This normalising action is the defining characteristic that separates adaptogens from both stimulants and sedatives.

Key Adaptogenic Botanicals

Ashwagandha (Withania somnifera) — The most commercially significant adaptogen, with KSM-66 and Sensoril as the leading standardised extracts. Clinical trials consistently demonstrate reductions in serum cortisol of 20–30% at doses of 300–600 mg daily.

Rhodiola rosea — Favoured for cognitive performance and fatigue reduction, with the SHR-5 extract (standardised to 3% rosavins, 1% salidroside) supported by European regulatory monographs.

Reishi (Ganoderma lucidum) — A medicinal mushroom traditionally used in Chinese medicine, now positioned in the functional food sector. Research focuses on triterpenoids and beta-glucans for immune modulation and stress resilience.

Eleuthero (Eleutherococcus senticosus) — The original Soviet adaptogen, sometimes called Siberian ginseng. Evidence supports mild improvements in physical endurance and stress tolerance, though clinical data is less robust than for ashwagandha or rhodiola.

Holy Basil (Ocimum tenuiflorum / Tulsi) — An Ayurvedic staple with emerging evidence for anxiolytic and anti-inflammatory effects. Ursolic acid and eugenol are key active compounds.

Schisandra chinensis — A berry used in traditional Chinese and Russian medicine. Its lignans (schisandrins) appear to support liver function and cognitive clarity under stress, with particular interest from the nootropic segment.

Mechanism of Action: The HPA Axis

The hypothalamic-pituitary-adrenal (HPA) axis is the body's central stress-response system. When a stressor is detected, the hypothalamus releases corticotropin-releasing hormone (CRH), which signals the pituitary gland to secrete adrenocorticotropic hormone (ACTH), which in turn stimulates cortisol production from the adrenal glands. Chronic stress dysregulates this feedback loop, leading to persistently elevated or blunted cortisol.

Adaptogens appear to modulate HPA axis activity at multiple points. Ashwagandha's withanolides have been shown to attenuate CRH signalling, while rhodiola's salidroside influences ACTH sensitivity. The net effect is a more measured cortisol response — neither suppressed nor excessive — which researchers describe as "stress-response optimisation."

Inflammatory Pathways and Neurotransmitter Effects

Beyond the HPA axis, adaptogens interact with inflammatory and neurotransmitter pathways. Many adaptogenic compounds inhibit NF-κB, a master regulator of inflammatory gene expression, thereby reducing pro-inflammatory cytokines such as IL-6 and TNF-α. This anti-inflammatory action may partly explain the fatigue-reduction effects reported in clinical trials.

On the neurotransmitter front, ashwagandha modulates GABAergic signalling (contributing to its calming effects), while rhodiola influences serotonin and dopamine metabolism. Schisandra has demonstrated acetylcholinesterase inhibition in preclinical models, suggesting potential cognitive benefits. These multi-target mechanisms differentiate adaptogens from single-pathway pharmaceuticals and underscore both their therapeutic promise and the complexity of standardising clinical outcomes.

What This Means for the United Kingdom

UK supplement manufacturers face a nuanced regulatory environment for adaptogen claims. The MHRA permits traditional herbal registration (THR) for certain botanicals including rhodiola, but ashwagandha remains without a formal UK monograph despite its commercial dominance. Brands marketing adaptogens in the UK must navigate between food supplement regulations and traditional herbal medicine pathways, with the Advertising Standards Authority actively scrutinising stress-related health claims. For B2B buyers sourcing adaptogenic raw materials, this means prioritising extracts with robust clinical dossiers and clear regulatory pathways to avoid costly compliance issues post-formulation.

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