Most of the studies on Ashwagandha have been performed in rats and mice. In one study, for example, administration of 2.5 mg/kg of an isolated "Withanolide" compound, 1-oxo-5beta, 6beta-epoxy-witha-2-ene-27-eth-oxy-olide, resulted in reduced indices of stress from exposure to cold, hypoxia, and restraint. Another study found that the stress-related responses (glucose intolerance, increase in plasma corticosterone levels, gastric ulcerations, male sexual dysfunction, etc.) of rats exposed to random foot shocks were attenuated by 25 - 50 mg/kg doses of Withania, administered 1 hour before.
Ashwagandha may also have anti-depressant effects. One study demonstrated that daily doses of 20 and 50 mg/kg of the withanolide fraction had similar effects to the benzodiazepine drug lorazepam on rat behavior in "elevated plus-maze, social interaction and feeding latency in an unfamiliar environment" tests.
Some of its positive effects may be due to its antioxidant activity. Rats given injections of 10 - 20 mg/kg of glycowithanolides for 21 days, had increased levels of endogenous antioxidants (superoxide dismutase, cata-lase and glutathione peroxidase) in their brains.
There are also antimicrobial, antiosteoporotic, antitumor, neuroprotective and immune-stimulating properties. Feeding 0.75 - 1.5 g/day of the root powder to rats also reduced cholesterol in hypercholesterolemic rats.
One of the more interesting properties of Ashwagandha may be its ability to increase levels of thyroid hormones. Mice gavaged with 1.4 g/kg root extract for 20 days had increased serum levels of T3 and T4, along with reduced hepatic lipid peroxidation. There is even a case report of thyrotoxicosis in a woman taking a supplement containing Ashwagandha.
As I've often pointed out, rats and mice aren't people. While these studies look interesting and support the traditional use of the herb, they're far from conclusive. There are very few human studies that provide any indication of benefits to health or performance at doses normally found in bodybuilding supplements.
One of the few human studies involved an Indian commercial supplement, RA-11, which is used to treat arthritis. The 32-week trial demonstrated significantly reduced pain and increased knee function in patients receiving the supplement vs. those receiving the placebo. One flaw, however, was that RA-11 contains several other herbs in addition to Ashwagandha, so it's difficult to draw firm conclusions from this clinical trial.
u While these studies look interesting and support the traditional use of the herb, they're far from conclusive. There are very few human studies that provide any indication of benefits to health or performance at doses normally found in bodybuilding supplements. ^
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