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Ashwagandha vs Rhodiola Rosea — Trial Data

Ashwagandha and Rhodiola Rosea are both classified as adaptogens and have separate human RCT literatures. This page reports the trial and meta-analysis data behind each, attributed to its source, and notes where a commonly repeated figure could not be traced to a citation.

On this page
  1. 1.Mechanism
  2. 2.Ashwagandha: Human Trial Evidence
  3. 3.Rhodiola Rosea: Human Trial Evidence
  4. 4.Traditional Use
  5. 5.Adverse Events
  6. 6.Evidence Level
  7. 7.Reading These Trials Together
  8. 8.FAQ
  9. 9.References

Mechanism

Ashwagandha (Withania somnifera) is reported to modulate the HPA axis (hypothalamic-pituitary-adrenal axis), the body's central stress-response system, with a meta-analysis reporting a significant reduction in serum cortisol across pooled RCTs (Fornalik et al. 2026, PMID 41740946).

Rhodiola rosea is reported in the trial literature to affect stress-response pathways including Hsp70 (heat shock protein 70) activation and cortisol-synthesizing enzyme inhibition; the mechanistic data on these specific pathways is largely preclinical, while the human trials cited below measured behavioral and hormonal outcomes (fatigue indices, burnout scores, cortisol response to awakening) rather than the mechanism directly.

Ashwagandha: Human Trial Evidence

Cortisol and stress: Chandrasekhar et al. 2012 (Indian J Psychol Med, PMID 23439798), a 60-day double-blind RCT in 64 adults with chronic stress, found 300 mg of a high-concentration root extract twice daily produced a significant reduction in serum cortisol (P=0.0006) and stress-assessment scale scores versus placebo. A 2026 meta-analysis (Fornalik et al., Planta Med, PMID 41740946) pooling 23 RCTs (n=1,706) found a significant overall cortisol reduction (SMD −1.18, P<0.04) and increased serotonin (MD 31.75 ng/mL, P<0.01), with subgroup analysis suggesting a dose-response relationship by withanolide content.

Testosterone and strength: Wankhede et al. 2015 (J Int Soc Sports Nutr, PMID 26609282), an 8-week RCT in 57 young men undergoing resistance training, found ashwagandha (300 mg twice daily) associated with significantly greater increases in bench-press 1RM (46.0 kg vs. 26.4 kg placebo, P=0.001), leg-extension 1RM (14.5 kg vs. 9.8 kg placebo, P=0.04), testosterone (96.2 ng/dL vs. 18.0 ng/dL, P=0.004), and reduction in body fat percentage (3.5% vs. 1.5%, P=0.03). The 2026 meta-analysis (PMID 41740946) found a significant gender-specific testosterone increase in men (MD 57.43 ng/dL) but not in women (MD 5.09 ng/dL), with no effect on estradiol in either gender. The same meta-analysis found no effect on TSH or T3, with a modest T4 increase (MD 0.61 µg/dL, P=0.02).

Rhodiola Rosea: Human Trial Evidence

Darbinyan et al. 2000 (Phytomedicine, PMID 11081987), a double-blind crossover trial in 56 physicians during night duty, tested a standardized SHR-5 extract against placebo over repeated two-week periods and found a statistically significant improvement in a composite fatigue index of associative thinking, short-term memory, calculation, and audio-visual perception speed, with no reported side effects.

Olsson et al. 2009 (Planta Med, PMID 19016404), a randomized, double-blind, placebo-controlled, parallel-group trial in 60 adults meeting diagnostic criteria for stress-related fatigue syndrome, tested SHR-5 extract at 576 mg/day over 28 days. Both groups improved on several measures (a placebo effect), but the treatment group showed significantly greater improvement specifically on Pines' burnout scale and several attention measures (omissions, commissions, and reaction-time variability on a continuous performance test), along with a significant difference in cortisol response to awakening stress between groups. No serious side effects attributable to the extract were reported.

AshwagandhaRhodiola Rosea
Primary Mechanism (Reported)HPA axis (hypothalamic-pituitary-adrenal axis) modulation; meta-analysis reports reduced serum cortisol (Fornalik et al. 2026)Reported to activate Hsp70 (heat shock protein 70) and modulate cortisol-synthesizing enzymes; mechanism data is largely preclinical
Studied ForStress, anxiety, cortisol, testosterone (men), muscle strength alongside resistance trainingStress-related fatigue, mental performance under fatigue, sport-specific physical performance
Cortisol (Human RCT Data)Meta-analysis of 23 RCTs (n=1706): SMD &minus;1.18 (P&lt;0.04) (Fornalik et al. 2026, PMID 41740946)Single placebo-controlled RCT (n=60) reported a significant difference in cortisol response to awakening stress vs. placebo (Olsson et al. 2009, PMID 19016404); no meta-analysis of comparable size located
Testosterone (Human RCT Data)Wankhede et al. 2015 (PMID 26609282, n=57 men, 8 weeks): testosterone rose 96.2 ng/dL vs. 18.0 ng/dL with placebo (P=0.004). Meta-analysis (PMID 41740946) reports a gender-specific increase in men (MD 57.43 ng/dL) but not women (MD 5.09 ng/dL)Not demonstrated in the trials reviewed for this page
Strength (Human RCT Data)Wankhede et al. 2015: bench-press 1RM gain 46.0 kg vs. 26.4 kg placebo (P=0.001); leg-extension 1RM gain 14.5 kg vs. 9.8 kg placebo (P=0.04)Not the primary outcome in the rhodiola trials reviewed for this page
Fatigue/Performance (Human RCT Data)Not the primary outcome in the ashwagandha trials cited hereDarbinyan et al. 2000 (PMID 11081987, n=56 physicians): reduced mental-fatigue index during night duty vs. placebo. Olsson et al. 2009 (PMID 19016404, n=60): reduced Pines&apos; burnout scale score vs. placebo over 28 days
Adverse Events (as reported)Wankhede et al. 2015: adverse events comparable between groups, no serious events reportedOlsson et al. 2009 and Darbinyan et al. 2000: no serious side effects attributed to the extract reported

Traditional Use

Ashwagandha has a documented history of traditional use in Ayurvedic medicine, referenced as background in several of the trial reports cited above (e.g., Chandrasekhar et al. 2012, PMID 23439798). Rhodiola rosea has a documented history of traditional use in Scandinavian and Russian folk medicine for fatigue and physical resilience. In both cases, this traditional use is reported here as historical context only — it is not clinical trial evidence, and is kept separate from the RCT data reported above.

Adverse Events

Ashwagandha: Chandrasekhar et al. 2012 reported adverse effects as mild and comparable between the ashwagandha and placebo groups, with no serious adverse events. Wankhede et al. 2015 reported no serious adverse events over the 8-week trial.

Rhodiola rosea: Darbinyan et al. 2000 and Olsson et al. 2009 both reported no serious side effects attributable to the extract over their respective trial periods.

Evidence Level

AshwagandhaRhodiola Rosea
LevelHuman RCT (individual trials and a 23-trial meta-analysis)Human RCT (individual trials; no comparably sized meta-analysis located)
BasisChandrasekhar et al. 2012 (PMID 23439798); Wankhede et al. 2015 (PMID 26609282); Fornalik et al. 2026 meta-analysis (PMID 41740946)Darbinyan et al. 2000 (PMID 11081987); Olsson et al. 2009 (PMID 19016404)

The ashwagandha and rhodiola trials cited above enrolled different populations (chronically stressed adults, resistance-trained young men, night-shift physicians, adults with diagnosed fatigue syndrome), used different extracts and doses, and measured different outcomes. They are not head-to-head comparisons of the two herbs, and none of the trials reviewed for this page tested ashwagandha and rhodiola against each other in the same population.

FAQ

What is the actual human trial evidence for ashwagandha and cortisol?

A 2026 systematic review and meta-analysis (Fornalik et al., Planta Med, PMID 41740946) pooled 23 randomized, placebo-controlled trials (1,706 patients) of oral ashwagandha and found a significant reduction in cortisol (SMD −1.18, P<0.04), with subgroup analyses suggesting a dose-response relationship tied to withanolide content. An earlier RCT (Chandrasekhar et al. 2012, PMID 23439798; n=64) reported a significant reduction in serum cortisol (P=0.0006) after 60 days of 300 mg twice daily versus placebo, alongside reduced scores on stress-assessment scales. A prior version of this page stated “multiple RCTs confirm 20–30% cortisol reduction” without a citation; that specific percentage range could not be traced to a source and has been removed. The meta-analysis figure (SMD −1.18) is reported here instead, since it is a real, sourced effect size — not a directly comparable percentage.

What is the human trial evidence for ashwagandha and testosterone?

Wankhede et al. 2015 (PMID 26609282), an 8-week RCT in 57 young men undergoing resistance training, found testosterone rose 96.2 ng/dL in the ashwagandha group versus 18.0 ng/dL with placebo (P=0.004), alongside greater 1RM strength gains on bench press and leg extension. The 2026 meta-analysis (Fornalik et al., PMID 41740946) found ashwagandha increased testosterone in men (MD 57.43 ng/dL) but not in women (MD 5.09 ng/dL), a statistically significant gender difference. A prior version of this page stated “10–15% increases in testosterone, men” without a citation; that percentage range could not be traced to a source and has been removed in favor of the absolute figures above.

What dose of ashwagandha was used in these trials?

Doses varied by trial. Chandrasekhar et al. 2012 (PMID 23439798) used 300 mg of a full-spectrum root extract twice daily (600 mg/day total). Wankhede et al. 2015 (PMID 26609282) used the same 300 mg twice-daily protocol. A prior version of this page stated a “300–600mg KSM-66 daily” dosing range; the trials reviewed for this page used a total of 600 mg/day of the extract studied (not specifically branded as KSM-66 in every trial), so that branded figure has been replaced with the doses each cited trial actually used.

What does the human trial evidence show for rhodiola rosea and fatigue?

Darbinyan et al. 2000 (Phytomedicine, PMID 11081987), a double-blind crossover trial in 56 physicians during night duty, found a statistically significant improvement in a composite mental-fatigue index during the two-week treatment period versus placebo, using a standardized SHR-5 extract. Olsson et al. 2009 (Planta Med, PMID 19016404), a randomized, placebo-controlled, parallel-group trial in 60 adults with stress-related fatigue, found the SHR-5 extract (576 mg/day) produced significant improvement on Pines' burnout scale and several attention measures compared with placebo over 28 days, along with a significant difference in cortisol response to awakening stress between groups.

What is traditional use versus clinical evidence for these herbs?

Ashwagandha has a documented history of use in Ayurvedic medicine, referenced as background context in Chandrasekhar et al. 2012 (PMID 23439798) and other trial reports; that traditional use is not itself clinical evidence and is reported here only as historical context, separate from the RCT data cited above. The same distinction applies to rhodiola rosea's traditional use in Scandinavian and Russian folk medicine, which is likewise reported as background rather than trial evidence.

References

  1. Chandrasekhar K, Kapoor J, Anishetty S. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian J Psychol Med. 2012;34(3):255-262. https://pubmed.ncbi.nlm.nih.gov/23439798/
  2. Wankhede S, Langade D, Joshi K, Sinha SR, Bhattacharyya S. Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. J Int Soc Sports Nutr. 2015;12:43. https://pubmed.ncbi.nlm.nih.gov/26609282/
  3. Fornalik M, Malkiewicz A, Adamczak D, Nawrocki F, Zielinska A, Mondal SA. Hormonal Modulation with Withania somnifera: Systematic Review and Meta-Analysis of Randomized-controlled Trials. Planta Med. 2026;92(8):790-805. https://pubmed.ncbi.nlm.nih.gov/41740946/
  4. Darbinyan V, Kteyan A, Panossian A, Gabrielian E, Wikman G, Wagner H. Rhodiola rosea in stress induced fatigue--a double blind cross-over study of a standardized extract SHR-5 with a repeated low-dose regimen on the mental performance of healthy physicians during night duty. Phytomedicine. 2000;7(5):365-371. https://pubmed.ncbi.nlm.nih.gov/11081987/
  5. Olsson EM, von Schéele B, Panossian AG. A randomised, double-blind, placebo-controlled, parallel-group study of the standardised extract shr-5 of the roots of Rhodiola rosea in the treatment of subjects with stress-related fatigue. Planta Med. 2009;75(2):105-112. https://pubmed.ncbi.nlm.nih.gov/19016404/
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