Adaptogens: What They Are, What the Research Shows, and Which Ones Are Actually Worth Taking
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Adaptogens have moved from the shelves of health food shops into mainstream wellness, appearing in everything from dedicated supplements to coffee creamers and energy drinks. The claims that follow them are significant: stress relief, better energy, improved sleep, reduced anxiety.
Some of those claims are well-supported. Some are less so. Here's an honest breakdown of what adaptogens actually are, what the evidence shows, and which ones are genuinely worth considering.
What Is an Adaptogen?
The term was first coined by Soviet scientists in the 1940s to describe substances that help the body resist various stressors; physical, chemical, or biological — while maintaining normal physiological function.
To qualify as an adaptogen, a substance must meet three criteria: it must be non-toxic at normal doses, it must produce a non-specific response that improves resistance to multiple types of stress, and it must have a normalising effect on the body regardless of the direction of the stressor.
In practical terms, adaptogens work primarily by regulating the hypothalamic-pituitary-adrenal (HPA) axis — the system that controls your body's stress response and cortisol output. When this system is chronically overactivated, as it often is in modern life, the downstream effects include fatigue, disrupted sleep, anxiety, cognitive fog, and reduced resilience. Adaptogens appear to help moderate this response.
The Two With the Strongest Evidence
Of the many plants marketed as adaptogens, two have accumulated the most robust clinical evidence.
Ashwagandha (Withania somnifera)
Ashwagandha has been used in Ayurvedic medicine for centuries and now has the strongest modern research base of any adaptogen. A 2024 meta-analysis of nine randomised controlled trials involving 558 participants found significant reductions in perceived stress, anxiety scores, and serum cortisol levels compared to placebo. A 2025 systematic review published in BJPsych Open confirmed these findings, concluding that ashwagandha supplementation is safe and effective in reducing stress and anxiety in adults, resulting in a statistically significant reduction of cortisol levels.
Research also supports ashwagandha's effects on sleep quality, particularly in stressed individuals — the mechanism appears to involve GABAergic activity, the same pathway targeted by some sleep medications. Some studies additionally suggest benefits for cognitive performance and mood.
The key active compounds are withanolides, found primarily in the root. Quality and standardisation matter significantly — high-quality supplements use a standardised extract with a defined withanolide content rather than plain ashwagandha powder, which offers inconsistent potency.
Rhodiola rosea
Rhodiola has a different profile from ashwagandha — where ashwagandha tends to be more calming and anxiety-reducing, Rhodiola is more energising and fatigue-focused. In 2011, the European Medicines Agency approved its traditional use for the temporary relief of stress-related fatigue, exhaustion, and weakness.
A review of over 70 human clinical trials found clear evidence that Rhodiola can effectively combat physical stress-related fatigue, low mood, anxiety, and depression, and may improve physical and mental working capacity. It works primarily through modulation of the central nervous system.
As with ashwagandha, standardised extract matters. Look for products standardised to 3% rosavins and 1% salidroside.
What About the Others?
Beyond ashwagandha and Rhodiola, the evidence base becomes thinner.
Holy basil (Tulsi) has a long history in Ayurvedic medicine for stress and mental clarity. Some preliminary evidence supports its anxiolytic effects, though the research is less robust than for ashwagandha.
Reishi mushroom shows promise for immune support and sleep quality. It's one of the better-evidenced functional mushrooms but still lacks the volume of human trials that ashwagandha has.
Eleuthero (Siberian ginseng) has historical use for fatigue and physical endurance, particularly in Soviet sports medicine. Research exists but is older and less consistent in methodology.
The honest position: ashwagandha and Rhodiola are where the evidence is strongest. Other adaptogens may offer genuine benefits, but the research base is smaller and more variable.
An Important Caveat on Safety
Adaptogens are generally well-tolerated, but they are not without considerations.
Ashwagandha may interact with thyroid medication — people on thyroid treatment should consult their GP before use. It is also not recommended during pregnancy. Denmark banned ashwagandha supplements in 2023 following a risk assessment, though this decision has been contested by other regulatory bodies, and the herb remains legal and widely sold in the UK.
Rhodiola may interact with SSRI antidepressants due to mild serotonergic activity. Anyone taking antidepressants should discuss this with their doctor before adding Rhodiola to their routine.
Both are considered safe for most healthy adults at standard doses. As with any supplement, the sensible approach is to start at the lower end of the recommended dose, introduce one adaptogen at a time, and give it at least four to six weeks before assessing the effect.
How to Choose an Adaptogen Worth Taking
Check for standardisation. This is the most important factor. A product that simply lists "ashwagandha" without specifying the extract type and withanolide percentage is offering you unknown potency. Look for KSM-66 or Sensoril for ashwagandha — these are the most researched branded extracts.
Match to your goal. Ashwagandha tends to suit people dealing with anxiety, stress, poor sleep, or cortisol dysregulation. Rhodiola tends to suit those dealing with fatigue, low energy, or difficulty concentrating under pressure. They can be used together — some evidence suggests they are complementary.
Be realistic about timelines. Adaptogens are not acute remedies. Most studies showing significant effects run for eight to twelve weeks. If you try an adaptogen for two weeks and notice nothing, that doesn't mean it isn't working — the timeline is longer than most people expect.
Key Takeaways
Adaptogens are a legitimate category of supplements with real evidence behind the best of them. Ashwagandha and Rhodiola rosea stand apart from the rest of the category in terms of research quality and volume. They work through the body's stress regulation system and are most useful for people dealing with chronic stress, fatigue, disrupted sleep, or anxiety.
Quality and standardisation matter enormously — the difference between a well-formulated ashwagandha extract and a cheap powder can be the difference between results and nothing.
At BATB we stock adaptogens that meet our standard for formulation and transparency. If you want our curated edit, you can explore it below.
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References
- BJPsych Open (2025). Ashwagandha Supplementation in Reducing Stress and Anxiety in Adults: A Systematic Review and Meta-Analysis.
- Explore NY (2024). Effects of Ashwagandha on Stress and Anxiety: A Systematic Review and Meta-Analysis.
- European Journal of Medicinal Plants. Rhodiola rosea and Ashwagandha: Anti-Stress Activity Review. Nektium / University of Las Palmas de Gran Canaria.
- Cureus (2025). Ashwagandha as an Adaptogenic Herb: A Comprehensive Review of Immunological and Neurological Effects.
- Pharmaceuticals (2025). Two Sides of the Same Coin: Adaptogenic Botanicals as Nutraceuticals.
- European Medicines Agency (2011). Herbal Monograph on Rhodiola rosea.