Ashwagandha in Brief
Withania somnifera, known as ashwagandha, is an adaptogenic herb from Ayurvedic medicine that has been used traditionally for a long time. A growing set of human trials now exists, chiefly on stress, sleep and exercise. The results are encouraging. Still, most trials were small, many took place in India, and many were funded or supplied by extract makers.
Quality varies a great deal from one ashwagandha supplement to the next. The root's main bioactive compounds are withanolides, and their concentration swings widely with growing conditions, plant age, extraction method and standardization. A product that claims 600mg of "Ashwagandha" could hold anything from a negligible to a meaningful amount of actual withanolides.
How KSM-66 Differs from Generic Ashwagandha
Ixoreal Biomed developed KSM-66, a proprietary full-spectrum extract of ashwagandha root. Only the root goes into it, and a water-based extraction process is used, which its maker calls "full-spectrum".
Here is how it stands apart from generic extract:
- Standardized potency: HPLC testing standardizes KSM-66 to 5% withanolides. Generic ashwagandha root powder typically gives no withanolide content at all.
- Published clinical studies: More human trials have been published on KSM-66 than on Sensoril, another branded extract, covering stress, sleep, strength and testosterone. Marketing totals differ, so we don't quote a number. Most of the trials were small, and the extract came from its maker.
- Specific doses: Most KSM-66 trials gave 300mg once or twice a day (300–600mg a day). Don't assume the results carry over to other ashwagandha extracts or to far lower doses.
- Same safety cautions: A brand name doesn't alter what's known about ashwagandha's risks. These include stomach upset and drowsiness, rare liver injury, possible effects on thyroid hormone, and interactions with sedative, thyroid, diabetes, blood pressure and immunosuppressant drugs. Avoid it in pregnancy. Safety beyond about three months isn't known.
What the Trials Found
Small placebo-controlled trials of KSM-66, mostly at 300mg twice daily, reported the following:
- Lower stress scores and lower serum cortisol than placebo, in a 60-day trial of 64 adults with chronic stress (Chandrasekhar et al., 2012)
- A bigger testosterone rise than placebo in an 8-week trial of 57 young men doing resistance training (Wankhede et al., 2015), though the groups' end-of-study levels did not differ significantly
- Larger strength gains than placebo (bench press and leg extension) in that same trial
- Better self-reported stress and anxiety in several small trials
- Improved sleep quality in some trials. A 2021 meta-analysis found clearer benefits at 600mg a day, after at least 8 weeks and in people with insomnia
All of these trials were small and mostly run in India, the manufacturer supplied the extract, and the abstract and results of the 2015 strength paper don't agree in places. One idea for how it might affect testosterone is through lower cortisol, because chronically high cortisol can suppress the hormonal signals behind testosterone production. That hasn't been proven.
Why the Dose Is So Important
The main published clinical data on KSM-66 used 600mg daily, usually split into two 300mg doses. Some products contain only 100–200mg of ashwagandha, or 17–33% of that 600mg daily amount. The effects seen in studies are less likely at far lower doses.
Each 4-capsule serving of Testosil has 300mg of KSM-66. Its directions permit up to two servings a day, which would match the 600mg in the main trials. Two servings would also push zinc and vitamin D above their adult upper limits, so ask your doctor first.