Ashwagandha and Cortisol: What the Trials Actually Measured
Ashwagandha root extract has been shown to reduce cortisol in randomized, placebo-controlled trials. The dose range studied runs roughly 240mg to 600mg a day, and the trials use extracts standardised for withanolide content. ONCE carries 600mg of root-only extract standardised to a minimum 5% withanolides, alongside 300mg magnesium glycinate and 200mg L-theanine.
Cortisol became the most talked-about hormone on the internet, and the supplement market answered by selling magnesium for it. Magnesium is a genuinely useful mineral with a real role in stress physiology. But here is the part the marketing skips: ashwagandha is the ingredient the cortisol trials were actually run on.
What the research measured
Multiple randomized, double-blind, placebo-controlled trials have measured cortisol as an endpoint in people taking standardised ashwagandha root extract, and reported reductions relative to placebo.
- A trial on root extract standardised to 2.5% withanolides at 500mg daily for 60 days reported a greater reduction in morning salivary cortisol than placebo, alongside changes in stress questionnaires.
- A separate trial using 240mg of a standardised extract reported greater reductions in morning cortisol versus placebo.
- Further trials on standardised root extracts have measured stress scales, sleep quality and cortisol together at doses in the same range.
The spec is the whole game
"Ashwagandha extract" on a label tells you almost nothing. Two things decide whether you are getting the material the research was run on.
1. Root only, no leaf
This is the line that matters most, and it is the one most commonly crossed. The clinical evidence base is built on root extract. The leaf is cheaper, it is far more abundant, and it also contains withanolides — which means leaf and stem material can be blended in and still hit a withanolide number on a certificate.
Ashwagandha sits on botanical adulteration watch lists for exactly this reason. ONCE specifies root only, with no leaf material.
2. A standardised withanolide percentage, verified per lot
Withanolides are the active compounds. An extract without a standardisation figure is an unknown quantity, because the dose printed on the label is the weight of the powder, not the amount of what is working.
| What the label says | What you actually know |
|---|---|
| "Ashwagandha 600mg" | Nothing. 600mg of powder of unknown strength. |
| "Ashwagandha extract 600mg" | Still nothing. No withanolide figure. |
| "Ashwagandha root extract 600mg, min. 5% withanolides" — ONCE | Root only, and at least 30mg of withanolides, verified by HPLC on the per-lot certificate. |
At 600mg and 5% withanolides, ONCE delivers more withanolide content than the 500mg-at-2.5% extract used in the trial above. That is the honest way to compare an ingredient to the research: match or exceed the spec, and say so plainly.
Why 600mg
| Daily dose | Status |
|---|---|
| Under 240mg | Below the commonly studied range. |
| 240 to 300mg | Bottom of the studied range. Supported. |
| 600mg — in ONCE | Top of the commonly studied range. |
The rest of the stack
ONCE does not carry ashwagandha alone, because the stress research does not sit on one ingredient.
Magnesium as true bisglycinate at 300mg elemental, the gentle chelated form rather than oxide. L-theanine at 200mg, studied for calm focus without sedation, which is why it pairs with coffee rather than fighting it. Glycine at 1g, which also does real work in the flavour system.
So the honest version of the cortisol pitch is not "this lowers your cortisol." It is: this contains the magnesium the market is selling you, plus the ingredient the cortisol studies were actually run on, at the top of its studied range, at a verified withanolide spec, plus theanine.
ONCE launches as a 30-serving tub. One scoop into 12 to 16 ounces of cold water, stir, drink it with breakfast. That is the entire routine, and it costs $60 this week, $99 at launch. There is no caffeine in it, so it works at 6am or 6pm.
Common questions
Does ashwagandha lower cortisol?
Randomized, double-blind, placebo-controlled trials on standardised ashwagandha root extract have measured cortisol as an endpoint and reported reductions relative to placebo, at daily doses of roughly 240mg to 600mg. That is a measured research finding rather than a guarantee of an individual result.
How much ashwagandha should I take for stress?
Trials measuring stress and cortisol have commonly used between 240mg and 600mg daily of a standardised root extract. ONCE carries 600mg of root-only extract standardised to a minimum 5% withanolides.
Do you need a branded ashwagandha extract?
No. What matters is the specification, not the brand name: root only with no leaf material, and a standardised withanolide percentage verified by HPLC on the per-lot certificate of analysis. Trials showing cortisol reductions have been run on both branded and non-branded standardised root extracts.
What is the difference between ashwagandha root and leaf extract?
The clinical evidence base is built on root extract. Leaf is cheaper and more abundant and also contains withanolides, so leaf and stem material can be blended in and still meet a withanolide figure on a certificate. Ashwagandha appears on botanical adulteration watch lists for this reason. ONCE specifies root only.
What are withanolides?
Withanolides are the active compounds in ashwagandha. A standardised extract declares its withanolide percentage, so 600mg at a minimum 5% withanolides delivers at least 30mg of withanolides. An extract with no standardisation figure gives you no way to know what you are getting.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is educational and is not medical advice; consult a physician before starting any supplement.