Adaptogens (Ashwagandha, Rhodiola, Ginseng): What the Term Means and What the Evidence Shows

“Adaptogen” is one of the most confident-sounding words in the supplement aisle, and it isn’t a scientific classification at all — it’s a term with a specific Soviet-era origin, no FDA-recognized meaning, and a habit of getting applied to a wide, evidence-mismatched group of herbs as though it were one thing. This article does two jobs: explain where the term actually comes from and why that matters, then walk through what the human trial evidence shows for the two most commonly marketed “adaptogens” this site hasn’t already covered in depth — Asian ginseng and rhodiola — plus a pointer to our existing, separate, in-depth coverage of ashwagandha.

The short version

• “Adaptogen” is not a regulatory or pharmacological category recognized by the FDA. The term was introduced by Soviet toxicologist Nikolay Lazarev in the late 1940s/1950s and formalized by pharmacologist Israel Brekhman in 1969 to describe substances that supposedly produce a “non-specific” resistance to stress, regardless of the stressor. It was never adopted into U.S. drug regulation, and products are sold under it as ordinary dietary supplements — evaluated for safety and labeling by the manufacturer, not for efficacy by any regulator, before sale.
• The FDA has actively issued warning letters (2020–2023) to supplement makers for illegal, unapproved health claims specifically tied to products marketed as “adaptogens” — this is a real, documented compliance history, not a hypothetical risk.
• Treating “adaptogen” as a single evidence category is itself misleading: the three most commonly cited herbs in this class — ashwagandha, ginseng, and rhodiola — have meaningfully different, non-interchangeable evidence bases, which is exactly why this article and our dedicated ashwagandha article treat them separately rather than as one claim.
• Asian ginseng has “a small amount of research” (NCCIH’s own phrasing) suggesting cognitive benefits in middle-aged — but not young — adults, and a 2023 review found ginseng alone may modestly help general fatigue, while combination ginseng formulas (not ginseng alone) showed benefit for chronic fatigue specifically. The majority of research shows no benefit for athletic performance.
• Rhodiola’s own federal regulatory-adjacent reviewer, NCCIH, states plainly: “we haven’t learned enough to say whether rhodiola is useful for any health-related purpose,” citing mostly low-to-moderate-quality research. A newer (2025) meta-analysis specific to athletic endurance found some positive signals — but it’s a narrower, more recent, sports-specific body of evidence than NCCIH’s broader “not enough evidence” verdict addresses.

Where “adaptogen” actually comes from, and why the FDA doesn’t use the word

This is worth spelling out because the term’s scientific-sounding structure does real marketing work that its actual history doesn’t support. Soviet toxicologist Nikolay Lazarev coined “adaptogen” in the late 1940s to describe substances thought to increase the body’s “non-specific resistance” to stress. Pharmacologist Israel Brekhman, building on Lazarev’s work, published a formal definition in 1969: an adaptogen causes a non-specific response, normalizes physiology regardless of what direction a stressor pushes the body, and doesn’t interfere with normal function beyond what’s needed to increase that resistance.

That’s a real historical research tradition, not a fabricated marketing term — but it was developed within a specific Soviet pharmacological research program and was never adopted as an FDA drug category or a formally recognized pharmacological classification in U.S. regulation. In practice, every product marketed as an “adaptogen” in the U.S. is regulated exactly like any other dietary supplement: under the Dietary Supplement Health and Education Act (DSHEA), meaning the manufacturer is responsible for safety and labeling claims, and the FDA does not evaluate or pre-approve efficacy before the product reaches shelves.

This isn’t just a technicality. Between 2020 and 2023, the FDA issued multiple warning letters specifically to manufacturers of supplements marketed as containing “adaptogens,” for illegal, unapproved health claims. That’s a concrete compliance history worth knowing, not a hypothetical concern — the word itself has drawn regulatory attention for the kinds of claims commonly attached to it.

Why “adaptogens” isn’t one evidence question

The practical consequence of the definitional looseness above: three herbs commonly sold under the “adaptogen” banner — ashwagandha, Asian ginseng, and rhodiola — have genuinely different evidence bases, and lumping them together as one claim (as most “adaptogen blend” marketing does) obscures real differences a careful reader should know about.

Ashwagandha has its own dedicated, in-depth article on this site — Ashwagandha for Stress and Cortisol: What the Trials Show — covering a 2022 meta-analysis (12 trials, 1,002 participants) showing a Moderate-rated effect on stress specifically, a Limited rating for anxiety as a distinct claim, and a documented liver-injury safety signal worth reading in full before considering an ashwagandha-containing product. We’re not re-covering that ground here; this article’s ashwagandha rating simply points to that piece.

Asian ginseng: a real but narrow, age-dependent, formula-dependent signal

NCCIH’s own review of Asian ginseng (Panax ginseng) research is more measured than typical marketing suggests, and worth reading closely rather than summarized as a flat “works” or “doesn’t work”:

• A small amount of research suggests Asian ginseng may improve cognitive function — abstract thinking, attention, arithmetic, reaction time — in middle-aged adults specifically, but not in young adults. Any memory benefit found has depended on ginseng being combined with ginkgo, not ginseng alone.
• A 2023 review of 19 studies (2,413 participants) found ginseng alone may have a small beneficial effect on general fatigue not tied to a specific disease — but for chronic fatigue specifically, benefit was seen with certain ginseng herbal formulas containing other ingredients, not with ginseng alone. NCCIH is explicit that not all research agrees even on this modest finding.
• The majority of research shows Asian ginseng does not improve athletic performance, directly contradicting a common marketing angle for the ingredient.
• Most clinical trials in this literature have been small (fewer than 200 participants) and short (under 3 months) — NCCIH itself calls for larger, longer, multicenter studies before the evidence can be considered strong for any of ginseng’s promoted uses.

Safety: short-term oral use (up to 6 months) at recommended doses appears safe for most people, though long-term safety hasn’t been well studied. Insomnia is the most common side effect. Uncommon but documented effects include severe rash, liver damage, and severe allergic reactions; ginseng may worsen autoimmune disorders and interfere with blood clotting, and it may lower blood sugar — a real interaction concern for anyone on diabetes medication. Some research suggests oral use during pregnancy may be unsafe (one component has caused birth defects in animal studies); NCCIH recommends consulting a health care provider before use during pregnancy, and little is known about breastfeeding safety.

Rhodiola: NCCIH’s own verdict is “not enough evidence” — and here’s the nuance worth adding

This is the plainest evidence statement of any ingredient this site has covered so far, worth quoting directly rather than softening: NCCIH’s rhodiola fact sheet states, “there isn’t enough reliable evidence to determine whether rhodiola or its components are useful for any health-related purpose,” adding that “most of the research in people is of low-to-moderate quality,” and concluding flatly, “we haven’t learned enough to say whether rhodiola is useful for any health-related purpose.” That is NCCIH’s most unequivocal “we don’t know” verdict of any ingredient reviewed on this site to date — rhodiola is promoted for athletic performance, mood, cognition, energy, and stress, and NCCIH’s position is that none of it is established.

The honest nuance worth adding, not smoothing over: a 2025 meta-analysis specific to athletic endurance (26 randomized controlled trials, 668 healthy participants, mostly younger adults, roughly a month of supplementation on average) found rhodiola supplementation associated with improvements in VO2 max, time to exhaustion, and time-trial performance, along with reduced markers of muscle damage and oxidative stress — with higher daily doses (above 600 mg) showing larger VO2 max improvements than lower doses. This is newer and narrower than NCCIH’s broader review (which predates it by several months and covers all of rhodiola’s promoted uses, not just athletic endurance specifically) — we’re presenting both rather than picking one, since they’re not actually answering the same question: NCCIH’s “not enough evidence for any health purpose” is the broader, more conservative verdict; the 2025 meta-analysis is a positive signal in one specific, narrower domain (endurance exercise performance) that NCCIH’s own review doesn’t specifically address in that dose-response detail.

Safety: NCCIH describes rhodiola as possibly safe for up to 12 weeks — the outer edge of what’s actually been studied, not a general long-term safety endorsement. Side effects can include dizziness, headache, insomnia, and either dry mouth or excess saliva production. An interaction with losartan (a blood pressure medication) has been reported, and separately, case-report literature describes a cardiovascular concern (tachyarrhythmia) when combined with prescription antidepressants — worth flagging plainly for anyone on SSRIs or similar medications. Little is known about safety in pregnancy or breastfeeding.

What we could not check

• We did not independently re-read the full text of the ginseng fatigue review (19 studies), the diabetes/cardiometabolic review (20 studies), or the 2025 rhodiola endurance meta-analysis (26 studies) — the figures above are drawn from NCCIH’s own summaries (for ginseng) and search-result summaries (for the rhodiola meta-analysis), not independent full-text reads on our end.
• We did not evaluate any specific commercial “adaptogen blend” product — most products combine multiple herbs (and often other ingredients) at doses that don’t necessarily match the studied doses of any single ingredient discussed here.
• We did not assess maca, ginkgo, holy basil, or other herbs sometimes marketed under the “adaptogen” umbrella — this article covers the three most commonly cited examples (ashwagandha via our separate article, ginseng, and rhodiola) rather than the full universe of herbs sold under this label.
• We did not verify the specific FDA warning letters referenced against the FDA’s own enforcement database directly — the 2020–2023 warning-letter pattern is drawn from a secondary legal/compliance summary, not FDA’s primary letter archive.

Our rating, and why

Ashwagandha (stress): Moderate. See our dedicated article for the full rating rationale, including why anxiety is rated separately and lower, and the documented liver-injury signal.

Asian ginseng (general fatigue, ginseng alone): Limited. A modest, not-universally-replicated pooled effect, per NCCIH’s own review of a 2023 systematic review — real enough to name, not strong enough to rate higher.

Asian ginseng (cognition in middle-aged adults): Limited. A real, age-specific signal in a small research base, explicitly not generalizable to younger adults per NCCIH’s own summary.

Rhodiola (any general health use): Anecdotal, following NCCIH’s own explicit “not enough evidence” conclusion — the most direct “we don’t know” verdict of any ingredient covered on this site so far. Rhodiola for athletic endurance specifically: Limited, based on the narrower, newer 2025 meta-analysis, kept distinct from the general-use rating above because it’s answering a different, more specific question with different (younger, athletic) trial populations.

If the newer rhodiola endurance evidence is echoed in NCCIH’s next review update, or if the ginseng age-dependent cognition finding is replicated in larger trials, these ratings will be revisited.

Sources

1. National Center for Complementary and Integrative Health (NCCIH). Asian Ginseng: Usefulness and Safety. Last updated February 2025. https://www.nccih.nih.gov/health/asian-ginseng
2. National Center for Complementary and Integrative Health (NCCIH). Rhodiola: Usefulness and Safety. Last updated April 2025. https://www.nccih.nih.gov/health/rhodiola
3. Li X, Yang M, Zhang YL, et al. Ginseng and ginseng herbal formulas for symptomatic management of fatigue: a systematic review and meta-analysis. Journal of Integrative and Complementary Medicine. 2023;29(8):468-482. (Cited via NCCIH’s own reference list and summary — see editorial notes.)
4. Naseri K, Saadati S, Sadeghi A, et al. The efficacy of ginseng (Panax) on human prediabetes and type 2 diabetes mellitus: a systematic review and meta-analysis. Nutrients. 2022;14(12):2401. (Cited via NCCIH’s own reference list.)
5. Rhodiola rosea endurance performance meta-analysis (26 RCTs, 668 participants). Frontiers in Nutrition. September 2025. (Read via search-result summaries — see editorial notes; the primary paper was not independently accessed in full, as PMC access was blocked.)
6. FDA warning letters to “adaptogen”-marketed dietary supplement manufacturers, 2020–2023. (Cited via a secondary legal/compliance summary describing this enforcement pattern — see editorial notes; FDA’s primary warning-letter archive was not independently searched.)
7. Our own Ashwagandha for Stress and Cortisol: What the Trials Show — full sourcing for ashwagandha specifically is documented there, not repeated here.