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In the ancient medicine system of Ayurveda, ashwagandha is regarded as a powerful and health-promoting herb. Also known as Withania somnifera, this shrub’s root and small, berry-like fruit have been used medicinally in India since at least 6,000 B.C., making it one of the oldest known medicinal herbs. This Ayurvedic favorite is traditionally used for anxiety and stress management, and to improve immunity, learning ability, blood sugar, cholesterol and sexual potency. Since the majority of ashwagandha studies have been completed on animals, more research is needed to best understand effectiveness, benefits and optimal dosing in humans.

Mental Health Benefits

Ashwagandha is considered an adaptogen -- a substance that helps the body cope with stress. Most of the available research on mental health benefits such as anxiety and mental alertness has been completed on animal subjects, but some human data is available. One example includes a study of 64 people with chronic stress who were given placebo pills or 300 mg twice daily of ashwagandha root extract. After 60 days, those taking ashwagandha had significant improvements in cortisol levels -- a physical marker of stress, and in measures of anxiety, sleep, depression and general well-being, according to research published in the July-September 2012 issue of “Indian Journal of Psychological Medicine.” A January 2014 paper published in “Pharmacognosy Research” showed that healthy men who were given 250 mg of leaf and root extract twice daily for 3 weeks had improvements in reaction time and task performance, compared to those taking a placebo.

Male Fertility Benefits

Ashwagandha supplementation may also provide benefits to male reproductive health. A study published in the August 2010 issue of “Fertility and Sterility” reported improved semen quality, increased testosterone levels and improved antioxidant levels in infertile men who supplemented with 5000 mg of ashwagandha root for 3 months. Another study using the same dose in men with stress-related infertility, published in the June 2011 issue of “Evidence-Based Complementary and Alternative Medicine,” demonstrated that treatment with this herb improved sperm quality, sperm count and reduced cortisol levels.

Other Potential Benefits

While many chemicals have been isolated from this plant, withanolides -- a group of steriods -- have received much research attention because of their role in activating certain hormones, according to a review published in the March 2004 issue of “Alternative Medicine Review.” Most of the beneficial effects connected to withanolides -- improved immunity, sedative properties, anti-inflammatory and antioxidant benefits -- have been demonstrated in animal studies. But limited human trials are intriguing.

A small study of adults with type 2 diabetes showed a 12 percent blood sugar reduction after a dose of 1000 mg ashwagandha 3 times daily for 30 days, according to a study published in the March 2000 “Indian Journal of Experimental Biology.” This same study demonstrated adults with elevated cholesterol experienced drops in total cholesterol and triglyceride levels -- 10 percent and 15 percent, respectively, after taking the same dose. Another study published in the April 2009 “Journal of Alternative and Complementary Medicine” found that after just 96 hours of use, subjects given ashwagandha had a significant increase in T cells and natural killer cells compared to the control group -- indicating a benefit to immunity. While this research is promising, larger research trials are needed to clarify benefits and use in humans.

Warnings and Precautions

Supplemental ashwagandha is traditionally available as a fine powder that can be mixed with food or liquids, and can also be purchased in pill and liquid form. However, not enough research has been completed on humans to determine effectiveness and safe, long-term dosing. According to the report published in “Alternative Medicine Review,” ashwagandha is generally considered safe, although large doses are linked to nausea, diarrhea and vomiting. In addition, ashwagandha has abortifacient properties, which means large doses could potentially lead to miscarriage -- so this supplement should be avoided in pregnancy. Finally, since this supplement is a mild central nervous system depressant, it may interact with alcohol, anti-anxiety drugs or sedatives. If you are under treatment for any medical or psychiatric problems, or take any prescription medications, talk with your doctor before starting supplemental ashwagandha.

Reviewed by Kay Peck, MPH, RD