Ashwagandha is one of the most heavily marketed nervous-system supplements on the market, and — unusually for a herb with that much marketing behind it — the human trial evidence for stress and cortisol is genuinely strong. It's also an ingredient where the specific extract matters far more than the name on the front of the bottle. Here's what the research actually shows, why the picture is more nuanced than "ashwagandha lowers cortisol," and where the form we currently sell falls short of the standard this article argues for.
What the trials show
A 2021 systematic review pooled seven randomized, placebo-controlled human trials covering 491 adults, all using ashwagandha for six to eight weeks.1 Across those trials, ashwagandha significantly reduced self-reported stress and anxiety levels compared to placebo, and — importantly, because this is an objective, measurable biomarker rather than a self-report — significantly reduced serum cortisol levels compared to placebo. A separate randomized, placebo-controlled trial measuring stress-relieving and pharmacological effects of a high-concentration ashwagandha extract found consistent results using validated stress-scale and cortisol measurements.2 A further randomized, double-blind, placebo-controlled trial in healthy, stressed adults extended the picture to cognitive function, finding measurable improvements on tasks related to attention and processing speed alongside the stress reduction.3 A separate meta-analysis of five trials (372 adults) found a small but statistically significant improvement in sleep quality, with the effect more pronounced at higher doses and longer duration of use.1
Ashwagandha is one of the few adaptogens where the cortisol drop shows up in blood tests, not just on a stress questionnaire.
The part that gets lost in translation: extract matters
Here's the detail that most ashwagandha marketing glosses over. Of the seven trials in that 2021 review, three used a specific standardized root extract called KSM-66, two used a different standardized root-and-leaf extract (Sensoril/Shoden), and one used plain whole-root powder at a much higher dose (12,000mg/day, roughly equivalent to 6,000mg of powder) to get a comparable effect.1 Doses studied ranged from 240mg to 1,250mg/day of extract, and the review specifically noted that benefits were more consistent at 500-600mg/day than at lower doses. In other words: "ashwagandha" on a label is not one thing. A capsule of generic root powder at an arbitrary dose is not equivalent to the standardized, tested extracts that produced these results — the plant species is the same, but the concentration of active withanolides, and therefore the dose that was actually studied, is not.
The practical upshot: check the label for "KSM-66" or "Sensoril/Shoden" by name and a dose in the 500-600mg/day range. If a product just says "ashwagandha root powder" with no standardization and no withanolide percentage, it isn't the thing the trials tested — and the effect size may not transfer. This is also why comparing two "ashwagandha" products by price per capsule is close to meaningless; a 500mg capsule of a standardized 5% withanolide extract and a 500mg capsule of raw root powder are not delivering the same active dose, even though the label looks identical at a glance.
Testosterone and male reproductive health: a newer, narrower line of evidence
Beyond stress and sleep, a smaller but growing body of research has looked specifically at KSM-66 and male reproductive hormones. A randomized, double-blind, placebo-controlled trial published in Health Science Reports in 2022 gave 50 healthy men (average age 35) either 300mg of KSM-66 ashwagandha root extract twice daily (600mg/day total) or placebo for eight weeks.4 The ashwagandha group saw a 17% increase in serum testosterone, compared to a 2% increase in the placebo group, alongside a 40% improvement in self-reported sexual-function scores (DISF-M) versus 25% in the placebo group. Prolactin levels didn't change in either group, which matters because it suggests the effect isn't being driven by some unrelated hormonal disruption.
One trial of this size is a meaningful data point, not proof of a durable, population-wide testosterone effect — it needs replication in larger and more diverse samples before it belongs in a marketing headline. But it's consistent with the broader pattern in this ingredient's research: real, measurable, extract-specific, dose-specific effects that show up on objective bloodwork, not just on a mood questionnaire.
The safety side: rare but real liver case reports
No responsible discussion of ashwagandha is complete without addressing liver safety, because the case-report literature here is real and has grown over the past several years. The NIH's LiverTox database — a clinical reference on drug- and supplement-induced liver injury — documents roughly two dozen published cases of clinically apparent liver injury attributed to ashwagandha as of its most recent review, and assigns it a "likely cause" causality rating.5 The typical pattern is a cholestatic or mixed-pattern liver injury with jaundice, appearing two to twelve weeks after starting the supplement and usually resolving within one to four months of stopping it, though rare cases involving people with pre-existing liver disease have been more severe. This is not a reason for alarm at a population level — millions of doses have been consumed against a few dozen documented cases — but it is a reason to skip ashwagandha (or check with a doctor first) if you have any existing liver condition, drink heavily, or take other medications processed by the liver, and to stop and seek care if you notice unusual fatigue, dark urine, or yellowing skin or eyes while taking it. It's also worth noting that several of the case-series authors flagged product quality as a confounding factor: commercial ashwagandha supplements are not always tested for contaminants or verified to contain what the label claims, so a chain-of-custody certificate of analysis isn't just a purity nicety — it's part of what makes a liver-injury signal interpretable at all, rather than a mystery of "which ingredient in this blend did it."
Comparing the standardized extracts
| Form studied | Typical dose in trials | What it's evidenced for |
|---|---|---|
| KSM-66 (root extract) | 300-600mg/day | Stress, cortisol, sleep, and (one RCT) testosterone in men14 |
| Sensoril / Shoden (root + leaf extract) | 240-500mg/day | Stress and cortisol reduction1 |
| Generic whole-root powder | ~6,000-12,000mg/day to match effect | Weaker evidence base; much higher dose needed1 |
Where Proco's ashwagandha actually stands
This started as a straightforward sourcing problem, not an evidence problem. Ashwagandha's evidence is about as strong as any ingredient we cover — multiple independent RCTs, consistent effect sizes, an objective biomarker (cortisol, and now testosterone in at least one trial) backing up the subjective stress-scale data — and it fits our category (nervous-system and stress support) outright. But that strong evidence is specific to the standardized extracts actually used in the trials (KSM-66 or Sensoril/Shoden), not to ashwagandha root powder generally — a sourcing distinction, not an evidence-bar one.
Ashwagandha is in Sleep Support today, in root-powder form, inside an undisclosed blend rather than the standardized extract this article argues actually clears the bar. That's a real gap between our stated standard and what's on the shelf. Root-form ashwagandha stays in Sleep Support for now while we work through ingredient disclosure across the range; moving it to a studied extract (KSM-66 or Sensoril/Shoden) at a disclosed dose is on the roadmap, not shipped yet. Given the liver case reports above, once dosing is disclosed we'll also be direct on the label about who should talk to a doctor first.
References
- "Ashwagandha: Is it helpful for stress, anxiety, or sleep?" Office of Dietary Supplements, National Institutes of Health. ods.od.nih.gov
- "An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study." PubMed, 2019. pubmed.ncbi.nlm.nih.gov
- "Efficacy and Safety of Ashwagandha Root Extract on Cognitive Functions in Healthy, Stressed Adults: A Randomized, Double-Blind, Placebo-Controlled Study." PubMed, 2021. pubmed.ncbi.nlm.nih.gov
- "Effect of standardized root extract of ashwagandha (Withania somnifera) on well-being and sexual performance in adult males: A randomized controlled trial." Health Science Reports / PubMed, 2022. pubmed.ncbi.nlm.nih.gov
- "Ashwagandha." LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, NIH National Institute of Diabetes and Digestive and Kidney Diseases. ncbi.nlm.nih.gov
This article is for informational purposes only and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease. Speak with a healthcare provider before starting any new supplement, especially if you take medication or have an existing health condition.
Related reading: Why We Don't Sell "Brain Blends" (And What Actually Clears Our Bar).
Every ingredient we sell should be dosed and disclosed at the level its supporting human trials actually used — and we're currently moving ashwagandha the rest of the way there, from root powder to a studied extract at a clearly disclosed dose. Explore the current range at procohq.com.