Initial Posting: 06/16/18 Last update: 11/24/2018
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Summary: What You Need to Know About Ashwagandha Supplements
What It Is:
- Does it work? Preliminary studies suggest that ashwagandha may help reduce anxiety, improve physical and cognitive performance, and have other benefits. However, larger studies are needed for confirmation.
- How to choose? When choosing an ashwagandha product, look for a root powder or a root extract containing, respectively, at least 0.3% and 1.5% of withanolides — key marker compounds which may also play a role in the herb's activity.
- How much to take? Daily dosage for a root powder is typically 1 to 6 grams (1,000 mg to 6,000 mg). For extracts it is 500 mg to 1,500 mg. A daily dose should provide at least 6 mg of withanolides — typically between 10 mg and 30 mg has been used in most studies.
- What did testing find? Many products contained lower amounts of withanolides than expected and only 56% of the products selected for testing were Approved. The amount of withanolides in a suggested daily serving ranged from just 0.57 mg to as much as 95.3 mg. The cost to obtain 6 mg of withanolides ranged from just 7 cents to $1.24. Price was not an indicator of quality. (See What CL Found).
- Best products? Several products were Approved for Quality and provide doses of withanolides consistent with efficacy in clinical studies. Among these, one product was selected as a Top Pick, offering superior strength and at low cost for withanolides. Several additional products represent good, well-priced alternatives.
- Safety: Ashwagandha has generally been found to be safe, but minor gastrointestinal or allergic reactions can occur. For more details, see Concerns and Cautions.
Ashwagandha (Withania somnifera) is an herb grown in India and in certain regions of Nepal. The roots contain withanolides, which are compounds thought to be responsible for some of the herb's effects (Prabhakaran, Pak J Pharm Sci 2012). Ashwagandha is sometimes referred to as "Indian ginseng" because it is thought to have similar "adaptogen" qualities, such as modulating the immune system and supporting the body's response to stress. It is also sometimes referred to as "winter cherry," but should not be confused with another plant, Physalis alkekengi, which is also commonly referred to as "winter cherry."
What It Does:
A number of small, short-term studies suggest a variety of potential uses for ashwagandha, but larger, long-term studies are needed to confirm these findings.
Clinical studies suggest that ashwagandha can reduce anxiety and stress. One randomized, double-blind study of 75 middle-aged adults with moderate to severe anxiety found that anxiety was dramatically reduced, and fatigue, motivation and concentration significantly improved, in those who received 300 mg of ashwagandha root extract (standardized to 1.5% withanolides) twice per day (a total daily dose of 600 mg ashwagandha extract containing 9 mg of withanolides), plus a daily multivitamin for 12 weeks (Cooley, PLOS One 2009). A second group of patients in the study who, instead, received a weekly psychotherapy sessions and a placebo, had a smaller reduction in anxiety. Both groups were encouraged to reduce their intake of stimulants (caffeine, chocolate, tobacco, etc.) and were instructed in deep-breathing exercises.
A small study among people with generalized anxiety disorder, panic disorder, and anxiety mixed with depression, found that those who took ashwagandha extract (two to six 250 mg tablets per day, for a total daily dose of 500 to 3,000 mg — amounts of withanolides not specified) for 6 weeks had significant improvement compared to those taking a placebo (Andrade, Indian J Psychiatry 2000).
Ashwagandha has been used and promoted for the treatment of insomnia, and even part of its scientific name —somnifera— refers to "sleep." Nevertheless, there are only animal experiments suggesting this effect and no clinical studies in people. However, as insomnia is often due to stress and anxiety, and ashwagandha may reduce these states, a beneficial effect on insomnia is certainly possible — but not proven.
A study among 66 men and women experiencing a worsening of symptoms of schizophrenia found that those who took a standardized ashwagandha extract (Sensoril, by Natreon Inc.) daily for three months had significant reductions in negative symptoms (emotional flatness, lack of social drive, etc.) and general symptoms (anxiety, depression, poor attention), although there was no improvement in hallucinations, delusions, disorganized speech and behavior, compared to placebo. Participants received 250 mg of ashwagandha extract twice daily for the first week, after which the dosage was increased to 500 mg of extract twice daily (likely providing at least 100 mg of withanolides). Sleepiness, epigastric discomfort, and loose stools were more common with the extract than with placebo (Chengappa, J Clin Psychiatry 2018).
A placebo-controlled clinical study in men with low sperm count found one capsule of ashwagandha extract taken three times daily (a total daily dose of 675 mg extract, 33.75 mg withanolides) increased sperm concentration, volume and motility by, respectively, 167%, 53% and 57% over 3 months. Compared to men who took a placebo, men who took the ashwagandha also had a significant increase in serum testosterone levels (Ambiye, Evid Based Complement Alterat Med 2013).
Sexual function in women
A 2-month study in 50 women ages 21 to 50 in India with low sexual desire and/or arousal found those who took 300 mg of ashwagandha extract after eating, twice per day, had significant improvements in overall sexual function, including arousal, lubrication, and satisfaction compared to placebo; although there was not a significant improvement in sexual desire. No adverse effects were observed (Dongre Biomed Res Int 2015). The researcher's theorized that ashwagandha may improve sexual function in women by reducing stress and potentially increasing testosterone levels (as has been shown in men), although this was not measured in the study. The extract used was KSM-66 from Ixoreal Biomed, containing 5% withanolides, which is about 2 to 3 times as concentrated as the products in this Review. (Products containing this extract were tested in this Review, however, they did not pass CL's testing, as they contained lower than expected amounts of withanolides).
A study in India found that ashwagandha improved thyroid function in men and women with subclinical hypothyroidism, defined as mildly to moderately elevated TSH levels (4.5 — 10 mIU/L) and normal levels of T3 and T4. Compared to placebo, those who took 300 mg of highly concentrated ashwagandha root extract (standardized to 5% withanolides) twice daily (total daily dose of 600 mg extract containing 30 mg of withanolides) for two months had an average decrease in TSH of 1.85 mIU/L and increases in T3 and T4 averaging 0.5 nmol/L and 18.8 nmol/L, respectively. (Sharma, J Altern Complement Med 2017). (The extract was KSM-66 from Ixoreal Biomed; see "Sexual Function in Women" above for products that contain this extract.)
There is also evidence that ashwagandha may increase the effects of thyroid medications, and may affect thyroid hormone levels even in people without thyroid disease (See Concerns and Cautions).
Small but well-controlled studies in India have shown ashwagandha to improve cognitive performance in adults. A study among healthy men found that taking two 250 mg capsules of ashwagandha extract with a glass of water each morning and evening (providing a total daily dose of 1,000 mg ashwagandha extract [SENSORIL, Natreon, USA] with at least 100 mg of withanolides) for 12 days significantly improved cognitive performance and reaction times compared to placebo (Pingali, Pharmacognosy Res 2014). A study among men and women with mild cognitive impairment (average age of 50) found that taking 300 mg of ashwagandha root extract (KSM-66 from Ixoreal Biomed, USA) twice daily (providing a total daily dose of 600 mg containing 30 mg of withanolides) for 8 weeks significantly improved many aspects of immediate and general memory, executive function, sustained attention, and information processing speed compared to placebo (which showed lesser improvements). Most improvements were not significant relative to placebo after 4 weeks and required 8 weeks. There was no significant effect on visuospatial processing, i.e., drawing images from memory and comparing rotated images (Choudhary, J Diet Supp, 2017).
A small study in healthy men and women ages 18 to 25 found that a daily dose of 500 mg of ashwagandha root extract (% withanolides not listed) taken one hour after a meal for 2 months significantly improved measures of physical performance and cardiovascular endurance, including velocity while sprinting, leg muscle strength, and VO2Max (a measure of aerobic capacity) compared to placebo (Sandhu, Int J Ayurveda Res, 2010). Similarly, a study of 38 recreationally active young men who began a resistance exercise program four days per week and took 500 mg of a standardized aqueous extract of ashwagandha roots and leaves with cold water every morning for three months increased upper and lower body strength compared to the same exercise regimen plus placebo. The extract, Sensoril (from Natreon, which funded the study), has a particularly high concentration of withanolides (no less than 10%) — providing at least 50 mg of withanolide glycosides per day (Ziegenfuss, Nutrients 2018).
Ashwagandha may have anti-inflammatory and analgesic properties. This was demonstrated in a small but well-controlled study in India that also used Sensoril. In the study, people with joint pain and discomfort from knee osteoarthritis took capsules containing 250 mg of extract, 150 mg of extract, or a placebo twice a day for 12 weeks. Significant reductions were observed on measures of pain, stiffness, and disability at both doses, although the 250 mg group showed earliest efficacy — at just 4 weeks. There were no adverse effects reported and no one dropped out of the study, although side effects were most common in the 250 mg group -- 20% of whom reported nausea. (Ramakanth, J Aruv Integ Med 2016) [The higher dose (250 mg) of extract used in this study would provide at least 50 mg of withanolides.]
Another clinical study found that two capsules (each containing 450 mg of ashwagandha root, 50 mg zinc complex, 100 mg of guggul and 50 mg of turmeric) taken 3 times daily for three months significantly reduced pain among patients with osteoarthritis, but no improvements were seen on x-ray (Kulkarni, J Ethnopharmacol 1991). Because the product contained a number of ingredients, it's not possible to know what the effect of ashwagandha alone might have been.
Quality Concerns and What CL Tested for:
In 2014, only 2 out of 8 ashwagandha supplements selected for review by ConsumerLab passed testing, indicating a major problem with quality in this category. Neither the Food and Drug Administration (FDA) nor any other federal or state agency routinely tests ashwagandha supplements for quality prior to sale.
In order to help consumers identify products of better quality, ConsumerLab.com once again purchased and tested ashwagandha supplements to determine whether they contained the labeled and expected amounts of withanolides and withanosides (referred to collectively in this report as withanolides) and did not exceed contamination limits for lead, cadmium and arsenic. All products in regular tablet/caplet form also underwent disintegration testing to check if they would break apart properly in solution. ConsumerLab.com also determined whether the label recommended dose provided at least 6 mg of withanolides.
See How Products Were Evaluated for more information on testing.