What Are Adaptogens? How They Work and What the Research Shows

Adaptogens have become increasingly popular in the supplement industry, particularly among people interested in managing stress, fatigue and recovery.

Ashwagandha, Rhodiola and Reishi are frequently grouped together under this term, although their chemical compositions, traditional uses and biological effects can be quite different.

The idea behind adaptogens is an interesting one. Rather than simply stimulating the nervous system or suppressing a particular biological response, certain natural compounds may influence how the body responds and adapts to physical and psychological stress.

There is a growing body of research supporting some of these effects, especially for particular herbal extracts. However, understanding what adaptogens actually do requires looking beyond the rather vague promises of balance and resilience that tend to dominate supplement marketing.

What Are Adaptogens?

Adaptogens are a group of natural substances, primarily derived from plants, traditionally associated with improving the body's ability to cope with different forms of stress.

The concept developed during Soviet research in the mid-20th century, when scientists began investigating substances that might improve tolerance to physical, chemical and psychological stressors.

Researchers proposed several characteristics that a substance should possess to qualify as an adaptogen:

• It should influence the body's response to different types of stress rather than acting against one specific stressor.

• Its effects should help maintain normal physiological function under challenging conditions.

• It should have a favourable safety profile when used appropriately.

The concept has since expanded to include numerous herbs and some medicinal mushrooms.

However, the term is not a precise pharmacological classification. Ingredients described as adaptogens may contain entirely different active compounds and interact with different biological pathways.

Ashwagandha and Rhodiola, for example, are both associated with stress-related research, but their chemical constituents and the outcomes investigated in clinical trials differ considerably.

The adaptogen concept provides a useful framework for discussing these ingredients, while their individual properties determine what they might actually offer.

Research: Panossian et al., Evolution of the Adaptogenic Concept from Traditional Use to Medical Systems.

How Do Adaptogens Work in the Body?

The human stress response involves an interconnected network of hormones, neurotransmitters and cellular signalling pathways.

One of its central components is the hypothalamic-pituitary-adrenal (HPA) axis.

When the brain perceives a stressful situation, the hypothalamus releases signalling hormones that stimulate the pituitary gland. This ultimately leads to the release of cortisol from the adrenal glands.

Cortisol plays an important role in regulating energy availability, metabolism, immune activity and the body's response to challenging circumstances.

It often receives negative attention, but cortisol is essential for normal physiology. Its concentration naturally fluctuates throughout the day, and an appropriate increase during stress is a perfectly normal response.

Problems can arise when stress is persistent and the systems regulating these responses become disrupted.

Adaptogens and the HPA Axis

Research suggests that certain adaptogenic herbs may influence aspects of HPA-axis activity, including cortisol responses and signalling pathways associated with stress adaptation.

Ashwagandha is among the better-studied examples. Several clinical trials have reported reductions in cortisol concentrations following supplementation with particular extracts.

Rhodiola has also been investigated for its effects on stress-related fatigue, mental performance and physiological stress responses.

These findings are supported by laboratory research examining interactions with neurotransmitter systems, cellular stress proteins and pathways involved in inflammatory signalling.

However, the precise mechanisms remain incompletely understood, and much of the detailed molecular research has been conducted in animals or isolated cells.

It's also inaccurate to suggest that every adaptogen simply lowers cortisol or automatically returns the body to an ideal state of balance.

Different extracts can produce different effects, and an observed change in a hormone concentration doesn't necessarily establish a corresponding improvement in health or wellbeing.

Research: Panossian and Wikman, Effects of Adaptogens on the Central Nervous System and Their Stress-Protective Activity.

Which Adaptogens Have the Most Interesting Evidence?

Several herbs have attracted scientific interest because of their traditional uses and the results of clinical studies.

The evidence is particularly interesting when specific extracts have been tested in controlled human trials.

Ashwagandha (Withania somnifera)

Ashwagandha is one of the most extensively researched adaptogenic herbs.

It has a long history of use in Ayurvedic medicine and contains several groups of biologically active compounds, including withanolides.

Modern research has focused particularly on perceived stress, cortisol concentrations, anxiety-related symptoms and sleep.

A 2024 systematic review and meta-analysis examined nine randomised controlled trials involving 558 participants.

The researchers reported statistically significant improvements in perceived stress and anxiety scores, alongside reductions in serum cortisol, compared with placebo.

Read the research: Effects of Ashwagandha on Stress and Anxiety: A Systematic Review and Meta-Analysis.

Subsequent reviews have also reported promising findings, although not every analysis has reached identical conclusions.

Differences in extract composition, dose, study duration and participant characteristics make direct comparisons difficult.

Nevertheless, Ashwagandha has a more substantial human research base than many ingredients marketed for stress-related applications.

Its withanolide composition is particularly relevant when comparing supplements, as different preparations may contain substantially different concentrations and profiles of these compounds.

Rhodiola Rosea

Rhodiola rosea has traditionally been used in parts of Europe and Asia, particularly in relation to fatigue, physical endurance and performance under challenging conditions.

Its principal studied compounds include rosavins and salidroside.

Unlike Ashwagandha, which is frequently associated with stress and sleep research, Rhodiola has attracted considerable interest for its potential effects on mental fatigue, attention and performance during periods of stress.

In a randomised, double-blind, placebo-controlled trial involving 60 participants experiencing stress-related fatigue, researchers examined a standardised Rhodiola extract over 28 days.

The treatment group demonstrated improvements in certain measures of fatigue and attention compared with placebo.

Read the study: A Randomised, Double-Blind Study of Rhodiola rosea in Stress-Related Fatigue.

Other studies have produced encouraging results, although systematic reviews have identified methodological limitations and inconsistent findings.

These studies suggest that Rhodiola deserves continued investigation, particularly in situations involving mental fatigue and sustained cognitive demands.

Extract quality is especially important. A product containing a small quantity of generic Rhodiola powder shouldn't automatically be considered equivalent to the standardised extracts used in clinical research.

Holy Basil (Tulsi)

Holy Basil, commonly known as Tulsi (Ocimum tenuiflorum), has a long history of use in traditional Indian medicine.

Its chemical composition includes various phenolic compounds and other phytochemicals, with composition varying according to the plant material and preparation.

Human research remains less extensive than that involving Ashwagandha, although there are encouraging findings.

A 2022 randomised, double-blind, placebo-controlled study investigated a standardised Holy Basil extract in 100 adults experiencing stress.

After eight weeks, the treatment group showed greater improvements in perceived stress and certain sleep-related measures compared with placebo.

The researchers also reported differences in cortisol responses during an experimentally induced stressful situation.

Read the study: Effects of Ocimum tenuiflorum Extract on Stress, Mood and Sleep.

The results provide a useful foundation for further research, although additional independent trials are needed to establish whether similar effects occur across different preparations and populations.

Reishi Mushroom (Ganoderma lucidum)

Reishi has a long history of use in traditional East Asian medicine and is frequently included in modern adaptogenic supplement formulations.

Its main groups of studied compounds include polysaccharides, particularly beta-glucans, and triterpenoids such as ganoderic acids.

Research into Reishi differs from much of the work involving Ashwagandha and Rhodiola.

Laboratory investigations have focused extensively on immune signalling, inflammatory pathways and the biological activity of its polysaccharides and triterpenoids.

Some human studies have also examined fatigue and wellbeing.

A randomised, placebo-controlled trial involving 132 participants investigated a Reishi polysaccharide extract over eight weeks. The researchers reported improvements in certain fatigue and wellbeing measures.

Read the study: A Randomised, Double-Blind Study of Ganoderma lucidum Polysaccharide Extract.

However, the broader clinical evidence remains limited, and results from one preparation cannot automatically be extended to every Reishi supplement.

Reishi's inclusion in the adaptogen category reflects its traditional use and proposed biological properties, rather than proof that it operates through precisely the same mechanisms as classical herbal adaptogens.

Do Adaptogens Actually Work?

There is credible evidence that certain adaptogenic extracts can influence measurable outcomes in human studies.

Ashwagandha has demonstrated promising results in research involving perceived stress and cortisol. Rhodiola has been investigated for stress-related fatigue and attention, while Holy Basil and Reishi have produced encouraging findings in smaller areas of research.

The evidence is strongest when considering particular extracts, doses and outcomes rather than the category as a whole.

A study involving a standardised Ashwagandha root extract, for example, doesn't establish that every Ashwagandha product will produce the same effect.

Similarly, findings involving a specific Rhodiola extract shouldn't be used to support claims about unrelated herbs simply because they share the adaptogen label.

The quality of the preparation matters alongside the quality of the research.

For anyone interested in using adaptogens, the most useful starting point is identifying which ingredient has actually been studied for the intended purpose and whether the supplement resembles the material used in that research.

How Long Do Adaptogens Take to Work?

There is no universal timeframe for adaptogenic effects.

Some studies investigating Rhodiola have examined changes in fatigue and attention over relatively short periods, while many Ashwagandha studies have assessed outcomes after six to eight weeks.

The Holy Basil trial discussed earlier also examined supplementation over eight weeks.

Different biological effects may emerge over different periods, and not every measurable change will necessarily be noticeable to the person taking the supplement.

For example, changes in a laboratory measurement such as cortisol don't automatically correspond to a noticeable difference in mood, sleep or energy.

The commonly repeated suggestion that adaptogens should produce noticeable benefits within one or two weeks isn't supported as a general rule across the category.

Clinical trial results are a more useful guide than a fixed expectation of when an ingredient should begin working.

What Should You Look for in an Adaptogen Supplement?

The quality of an adaptogenic supplement depends on considerably more than the name of the herb printed on the label.

Several characteristics are worth examining.

Botanical identity: The manufacturer should clearly identify the species used, preferably by its accepted scientific name.

Plant part: Roots, leaves and other plant structures can contain different concentrations of active compounds. Ashwagandha root extracts, for example, aren't necessarily equivalent to extracts containing substantial quantities of leaf material.

Extraction method: The solvents and extraction conditions used can influence the compounds present in the finished extract.

Standardisation: Some herbal extracts are standardised to particular constituents, such as withanolides in Ashwagandha or rosavins and salidroside in Rhodiola.

Dose: The quantity supplied should be considered alongside the extract's composition and the doses investigated in relevant research.

Testing and transparency: Appropriate identification, contaminant testing and analytical documentation help establish whether the product contains the material it claims to contain.

A high extraction ratio or an impressive percentage of one constituent doesn't automatically establish superior quality.

The composition of the finished ingredient and the evidence relevant to that particular preparation are more informative.

Are Adaptogens Safe?

Many adaptogenic herbs have been used traditionally for generations, and several have shown favourable tolerability in short-term clinical studies.

Nevertheless, their biological activity means that suitability can depend on the individual and the particular preparation.

Ashwagandha, for example, may interact with medications affecting thyroid function, blood pressure, blood glucose or the immune system. Rare cases of liver injury have also been reported, and its long-term safety remains insufficiently established.

The UK Food Standards Agency is reviewing the safety evidence for Ashwagandha in food supplements, including potential effects on thyroid function and the liver.

Food Standards Agency: Ashwagandha safety review.

Other herbal extracts may have different precautions and interaction profiles.

Anyone who is pregnant, breastfeeding, taking prescription medication or managing a medical condition should seek appropriate professional advice before using an adaptogenic supplement.

Combining several herbs also deserves consideration. Ingredients that are individually well tolerated aren't necessarily proven safe or more effective when taken together.

Is Shilajit an Adaptogen?

Shilajit is frequently described as an adaptogen, particularly in discussions of traditional Ayurvedic medicine.

However, its composition differs substantially from conventional herbal adaptogens.

Shilajit is a complex mineral-organic substance formed through natural processes involving organic matter and geological environments.

It contains a mixture of humic substances, including fulvic and humic acids, alongside minerals and various organic compounds.

Research has investigated its potential effects on cellular energy processes, exercise-related fatigue and other physiological outcomes.

Some of these findings are encouraging, although much of the mechanistic research remains preclinical and the available human studies are relatively limited.

Claims that Shilajit's fulvic compounds reliably enhance the absorption or transport of other supplements in humans aren't sufficiently established.

Shilajit can be considered within the broader discussion of traditional tonics and substances associated with physical resilience, but it shouldn't automatically be assumed to have the same mechanisms or effects as Ashwagandha or Rhodiola.

Its composition and safety also depend heavily on sourcing, purification and analytical testing.

For a more detailed examination, see our Shilajit Benefits Guide: What the Research Suggests and What People Get Wrong.

Where Adaptogens Fit Into a Supplement Routine

Adaptogens represent an interesting area of nutritional and botanical research, particularly for people interested in the relationship between stress, fatigue and physiological function.

Their potential value is increasingly supported by human studies, although the strength of the evidence varies between ingredients.

A sensible approach involves choosing an extract with relevant research behind it, understanding its composition and considering whether it is appropriate for the individual.

Sleep, nutrition, physical activity and the management of ongoing stress remain fundamental to health. Adaptogenic supplements can be considered alongside those foundations rather than as substitutes for them.

There is good reason to remain interested in adaptogens, particularly as research into their active compounds and physiological effects continues to develop.

The most convincing case for their use comes from the evidence associated with individual ingredients, rather than the increasingly broad promises attached to the category.

Written By

Written by Chris Simon, Founder of One Life Foods.

Chris has worked in the supplement industry since 2009 and is known for seeking out exceptional ingredients, products and formulations.

Read more about Chris and the story behind One Life Foods.