Adaptogen
Ashwagandha (KSM-66 / Sensoril)
Withania somnifera
Last reviewed
The adaptogen people reach for when stress feels relentless. It's the most studied root for everyday tension — standardized extracts like KSM-66 have, in several trials, eased perceived stress and cortisol against placebo.
Our pick, and why
Choosing a ashwagandha (ksm-66 / sensoril): how the options compare
The trials that produced ashwagandha's stress and cortisol results used specific standardized extracts, not generic powder — so that's what we screen for. Among these three, only the Sports Research product is built on a named, clinically-trialed extract: Shoden®, standardized to 35% withanolides, which is why it's our pick. The NOW Foods extract at least discloses its standardization (2.5% withanolides, 11 mg), but it's a generic, unbranded extract rather than one with its own trial evidence. The Jarrow extract states no withanolide content at all, so there's no way to confirm it matches what the research tested. Two honest caveats on our pick: Sports Research states the 500 mg total and the Shoden® standardization, but not how many milligrams of Shoden® that 500 mg contains — so we can't check it against the 120–240 mg used in the Shoden trials. And if you want the single most-studied option, a dedicated KSM-66 600 mg root extract remains the textbook choice.
How we judge these
A named, clinically-trialed standardized extract (KSM-66, Sensoril or Shoden) with the withanolide content stated, dosed in its studied range. Generic, unbranded 'root powder' is not the extract the trials used.
| Product | Product | Named extract | Withanolides | Plant part | Dose / serving | Meets it | Link |
|---|---|---|---|---|---|---|---|
| Our pick Sports Research Ashwagandha, 500 mg (Shoden®) | Shoden® | 35% (Shoden® standardization) | Root & leaf | 500 mg | ✓ | SportsResearch.com → | |
| NOW Foods Ashwagandha Extract | Generic (unbranded) | 2.5% (11 mg) | Root & leaf | 450 mg | — | Amazon → | |
| Jarrow Formulas Ashwagandha Extract | Generic (unbranded) | Not stated | Root | 300 mg | — | Amazon → |
- Sports Research Ashwagandha, 500 mg (Shoden®)Our pick
- Named extract
- Shoden®
- Withanolides
- 35% (Shoden® standardization)
- Plant part
- Root & leaf
- Dose / serving
- 500 mg
- Meets our criterion
- ✓
- NOW Foods Ashwagandha Extract
- Named extract
- Generic (unbranded)
- Withanolides
- 2.5% (11 mg)
- Plant part
- Root & leaf
- Dose / serving
- 450 mg
- Meets our criterion
- —
- Jarrow Formulas Ashwagandha Extract
- Named extract
- Generic (unbranded)
- Withanolides
- Not stated
- Plant part
- Root
- Dose / serving
- 300 mg
- Meets our criterion
- —
Specs verified against live listings at time of writing and can change — confirm on the product page. Links are affiliate links; details.
Ashwagandha has moved from Ayurvedic tradition to the clinical-trial literature more successfully than almost any other herb. Standardized root extracts have a respectable stack of randomized, placebo-controlled studies behind them showing reductions in perceived stress, anxiety-scale scores, and morning cortisol in chronically stressed adults.
It is, however, a stress herb, not a depression treatment — the research population is “stressed but healthy adults”, and that’s the honest frame for using it.
What to look for
- A named, standardized extract (KSM-66 or Sensoril) with withanolide content listed
- Root extract rather than cheap leaf-and-stem powder
- A consistent 6–8 week trial before judging whether it helps you