Ashwagandha

Ashwagandha is the common name for Withania somnifera. Trials generally test manufactured extracts rather than a single uniform product. A KSM-66 randomized trial in 64 stressed adults found larger 60-day improvements in perceived stress and morning cortisol than placebo [4]. Later pooled analyses agree more consistently on cortisol than on every subjective scale: a 2024 review reported benefits across stress measures, while a 2025 review found lower cortisol but no significant pooled Perceived Stress Scale effect [1][2].

Sleep evidence is modest. A KSM-66 trial in 60 adults with insomnia found better sleep outcomes after ten weeks at 300 mg twice daily [6]. A five-trial, 400-person meta-analysis found a small overall sleep benefit, particularly with at least eight weeks of treatment [3].

Exercise and body-composition claims need narrower wording. A KSM-66 resistance-training trial reported greater strength gains and a decrease in body-fat percentage [5]. A later Sensoril trial found greater strength gains but no significant difference in total fat mass or body-fat percentage [7]. A 2026 meta-analysis judged strength evidence low certainty and did not find a clear body-fat benefit [8].

Ashwagandha contains multiple withanolides and other constituents, so a whole extract is not one pharmacological molecule [4][9]. Cortisol reductions in stress trials are human observations, not proof of a unique receptor mechanism [4][9]. One small randomized trial in subclinical hypothyroidism found changes in TSH, T3 and T4 after root extract, which matters for thyroid-related cautions but does not prove treatment benefit in the general population [10].

KSM-66: Root only, standardized to at least 5% total withanolides by HPLC in the cited stress trial; its manufacturer supplied the extract [4]. The 300 mg twice-daily protocol appears in the stress, insomnia and training studies, but those outcomes were tested in different groups [4][5][6]. “Full spectrum” is a product description, not evidence that every ashwagandha preparation has the same effects.

Sensoril: An aqueous root-and-leaf extract studied at 500 mg once daily during resistance training. The STAR trial saw strength improvements, with no significant total-fat-mass advantage [7].

Shoden: A root extract standardized to 35% withanolide glycosides, studied at 240 mg once daily for stress. Its Hamilton anxiety score and cortisol improved versus placebo, whereas DASS-21 did not reach statistical significance [9]. The 35% glycoside figure cannot be directly compared with KSM-66's 5% total-withanolide figure because they quantify different constituent groups.

Short stress trials reported mostly mild adverse events and limited follow-up; the KSM-66 trial recorded six events on extract versus five on placebo, with no serious events [4]. This does not rule out rare harm. A five-case series linked ashwagandha to cholestatic or mixed liver injury appearing after two to twelve weeks [11]. An Indian series of eight suspected cases included severe liver injury and deaths in people with pre-existing liver disease [12]. The case reports do not establish the risk rate for any particular standardized extract.

The thyroid-hormone changes in a small trial support extra caution for people with thyroid disease or thyroid medicines [10]. The NIH fact sheet advises against use during pregnancy or breastfeeding.