Withania somnifera. An adaptogen from Ayurvedic medicine, now one of the most studied botanicals on the shelf. The evidence for stress and sleep is reasonable by supplement standards, which is a lower bar than it sounds.
What the research supports
Multiple randomized controlled trials in adults under stress have found reductions in self-reported stress and in morning cortisol compared with placebo, typically over 8 weeks. Trials on sleep quality have shown modest improvements in sleep onset and in how rested people feel. Most of these studies are small, many are funded by extract manufacturers, and the effect sizes are moderate rather than dramatic.
The dose that was actually studied
Most positive stress trials used 300 to 600 mg a day of a root extract standardized to withanolides (such as KSM-66), taken as one or two doses. Some sleep trials used a concentrated root-and-leaf extract (Shoden) at around 120 mg a day. Products that do not name the extract or state a withanolide percentage cannot be matched to what was tested.
What to look for on a label
- Root extract, with the plant part named
- A stated withanolide percentage
- A named standardized extract (KSM-66, Shoden or Sensoril) where the research was done on that extract
- Third-party testing, because ashwagandha is a root and roots take up heavy metals from soil
Who should not take it
- Anyone pregnant or trying to conceive. It is traditionally avoided in pregnancy.
- Anyone with a thyroid condition or on thyroid medication, because it can raise thyroid hormone levels.
- Anyone on sedatives, immunosuppressants, or medication for an autoimmune condition.
- Anyone with liver problems. Rare cases of liver injury have been reported, and you should stop and seek care if you develop jaundice, dark urine or unusual fatigue.
Our take
If you are dealing with ordinary life stress and want to try one botanical, this is a defensible choice for a time-limited trial of eight to twelve weeks, with your doctor informed. It is not a treatment for an anxiety disorder, and it is not something to take indefinitely without a reason.
Our picks
We compared five ashwagandha products against the research, from a KSM-66 capsule to an alcohol-free liquid. Read The Best Ashwagandha Supplements for the full breakdown.
