Adaptogens: ashwagandha, rhodiola and studies with sixty participants
The word adaptogen was coined in the mid-twentieth century for substances said to raise resistance to stress in general, without specifying to what. A definition with no edges is convenient to sell and awkward to test, which is why the literature is large and the conclusions are small.
A category defined so it cannot fail
The classical definition asks three things of an adaptogen: raise resistance non-specifically, normalise disturbed functions in whichever direction they are disturbed, and be harmless. The second clause is the interesting one. A substance that both raises and lowers a measure depending on where it started cannot be refuted by experiment — every result confirms it.
Because of that, the useful research does not study "adaptogens". It studies one plant at a time against one outcome at a time: anxiety, sleep, endurance. What holds the category together is tradition, not a shared mechanism.
Ashwagandha: where the data is thickest
Withania somnifera is the best-studied of the group, with enough trials to support systematic reviews. A review on anxiety and stress and a review on anxiety and insomnia both describe improvement on self-report scales relative to placebo.
The caveats come from the reviews themselves.
- Study size. A typical trial runs forty to eighty participants for eight weeks.
- Subjective outcomes. Questionnaire scores. A legitimate method, but sensitive to expectation, and a plant extract is hard to blind completely.
- Heterogeneous products. Different plant parts, extracts and doses. Pooling them into one estimate takes some stretching.
- Geography and funding. A large share of the work comes from one region and not infrequently involves manufacturers.
The cautious reading: there is a signal, it replicates reasonably well, and its size and durability over longer periods are unknown.
Rhodiola, ginseng and the rest
Considerably less to go on. Rhodiola has been studied for fatigue and mental performance with uneven results in small samples. Ginseng and eleuthero look similar: studies exist, replication is weak.
That is a description of the state of the field rather than a verdict. It is at the stage where "possibly" is a reasonable word and "proven" is not.
About cortisol
The stock claim is that adaptogens lower cortisol. In some trials that shift was indeed recorded. The problem is the significance attached to it.
Cortisol swings across the day and depends on sampling time, on sleep, and on what the person was doing an hour earlier. A single measurement says very little, and the link between the number on a lab report and how someone feels is not direct. A lower value on paper means neither an improvement in state nor that stress has been removed.
This is the same gap between surrogate endpoint and outcome discussed in the overview of biohacking claims.
What is in the capsule
A separate and practically larger issue. Plant extracts are variable raw material: active content depends on where the plant grew, which part was used and how it was extracted. Standardisation is not always claimed, and a buyer cannot check it.
Status compounds the problem. These products are sold as dietary supplements, where proof of efficacy is not required before market entry. What that means in practice is set out in supplements, vitamins and medicines.
Safety
"Natural" does not mean "harmless", and here that is not an abstraction. Cases of liver injury have been reported with ashwagandha, and it also affects thyroid function, which matters for anyone with a thyroid condition or on thyroid medication. It is not used in pregnancy.
Plant extracts in general tend to interact with medicines through liver enzymes, so with ongoing therapy the question belongs with a doctor rather than with product reviews.
How this connects to food
Barely at all, which is the point of mentioning it. Fatigue, poor sleep and "no energy" are explained far more often by short sleep, an inadequate diet or an iron deficiency than by the absence of a plant extract. Before tuning anything fine, it is worth checking the coarse: how much someone sleeps and how much they actually eat — see sleep and weight and daily calorie needs.
If after that someone still wants to try an adaptogen, that is a defensible decision made with open eyes: the expected effect is small, the evidence is thin, and the contents of the capsule cannot be verified.
Frequently asked questions
- Does ashwagandha work?
- Systematic reviews describe improvement on anxiety and stress scales versus placebo. The trials are small, the outcomes are self-reported and the products are heterogeneous, so the size and durability of the effect remain unclear.
- Do adaptogens really lower cortisol?
- Some trials recorded such a shift. Cortisol varies widely across the day and with sampling conditions, and the link between a lab value and how a person feels is not direct.
- How do adaptogens differ from medicines?
- By status. They are sold as dietary supplements: proof of efficacy is not required before market entry, and control over the content of active compounds is looser.
- Are they safe?
- Not automatically. Cases of liver injury have been reported with ashwagandha, and it affects thyroid function. Plant extracts can interact with medicines through liver enzymes, so ongoing therapy calls for a conversation with a doctor.
- What is worth checking before trying an adaptogen?
- Sleep duration, actual calorie intake and any deficiencies visible in blood work. Those causes of fatigue are far more common and can be addressed without buying anything.
Read next
- How dietary supplements differ from vitamins and medications — In a pharmacy, two packages of vitamin D sit on the same shelf.
- Sports supplements: creatine, glutamine, lecithin — The sports nutrition shelf is arranged so that expensive and useless products stand next to cheap and effective ones.
- How sleep loss affects appetite and weight — Sleep usually turns up in the last paragraph of a weight-loss article, phrased vaguely enough to be safe.
This article is for general information. It is not medical advice, a diagnosis, or a prescription for treatment or a diet, and it does not replace a consultation with your doctor. If you have a health condition, are pregnant, take medication, or follow a diet prescribed to you, decisions about food belong with your doctor.
Figures from regulations, guidelines and studies are given as they stood when this article was prepared and may since have changed; check them against the primary sources. This article is not advertising, an offer, or individual advice, and neither the author nor the site owner is responsible for decisions taken on the basis of it.