Ashwagandha is a dietary supplement derived from the root of the Ashwagandha plant. Also known as Indian Ginseng, Ashwagandha (Withania somnifera) is an herb extensively used in the traditional medicinal practices of India, specifically Ayurveda. The root of the Ashwagandha plant emits an aroma reminiscent of horses, hence the name "ashwa" (meaning horse) and "ghanda" (meaning smell).
Ashwagandha: A Nutritional Supplement with Numerous Claims but Limited Evidence
This herbal extract is often associated with potential benefits such as reduced anxiety, improved sleep quality, lowered cortisol levels, as well as enhanced strength and endurance performance. However, it is crucial to approach these claims with caution, as they may appear too good to be true. To assess the validity of such assertions, let us delve into the available research on Ashwagandha's effects on recovery and performance—the primary factors that attract athletes to this supplement.
Examining an In-Depth Study on Ashwagandha
One immediately noticeable aspect when reviewing scientific literature on Ashwagandha is the scarcity of studies conducted thus far. Moreover, most of the available studies are characterized by short durations and subpar methodologies. For instance, let's analyze a frequently cited study (1) that served as the initial performance study on Ashwagandha and was included in meta-analyses like the one conducted by Bonilla et al in 2021 (2).
Taking a Closer Look at an Ashwagandha Study
The study conducted by Sandhu et al (1) was published in the relatively obscure journal "International Journal of Ayurveda Research." A brief examination of the paper reveals several issues regarding its quality. Even someone with limited experience in paper review would quickly conclude that this study should have been rejected during the initial review process (assuming it underwent peer review).
The methods section is incomplete, lacking crucial details about the utilized techniques and processes. Standardization procedures are not mentioned, and there is a notable absence of any familiarization protocols. Consequently, various questions arise regarding the study's execution. Were the measurements taken at consistent times of the day? Did the subjects consume food in the hours preceding the trial? Was temperature and humidity adequately controlled? Furthermore, the study lacked a cross-over design, instead dividing forty subjects into four treatment groups, significantly reducing statistical power. Additionally, numerous units of measurements were omitted, and the reported decimal places failed to reflect measurement accuracy. Consider the following two examples:
Measurements
Average absolute power = 793.61 The unit of measurement is not specified, although the table or text presenting the numbers provides no clarification. Presumably, the unit is watts (J/s). However, can we genuinely measure this accurately to two decimal places?
Oxygen uptake
The study's most crucial measurement revolves around oxygen uptake. The provided method description is as follows: "Computer-controlled Vista Turbo trainer machine was used for evaluating breath by breath gas exchange kinetics. Peak oxygen consumption was measured using software turbofit version 5.04." This description is notably deficient in information. How was the machine calibrated? Were the numbers obtained from the machine verified and accurately converted into the presented figures?Regardless, the reported numerical values seem absurd, yet they were published. The reported oxygen uptake values range between 10 and 12 ml/kg/min.
However, it is highly unlikely for individuals to have a VO2peak of 10-14 ml/kg/min. These values only slightly surpass resting levels, which contradicts the expectations for young, healthy adults' VO2max. These findings constitute the study's primary outcome, and yet, it was included in a meta-analysis...
Another studie
This critique does not solely focus on one study. In another study, participants received a daily dosage of 500mg of an herbal extract for 12 weeks (3). This study followed a randomized, double-blind, placebo-controlled design. The subjects involved in this study were recreationally trained. Before and after the intervention, several strength measurements were conducted. Although a statistically significant increase in 1-repetition maximum was observed for both squat and bench press exercises, other measurements, including "the total of all strength measurements," did not yield significant differences.
It is important to acknowledge our tendency to favor positive findings while neglecting negative ones. However, the probability of false positives increases with the number of measurements, meaning that chance influences outcomes more frequently than anticipated.Some cite this study to support the claim that herbal extract consumption can enhance aerobic performance, which was measured through a 7.5 km cycling time trial. Nonetheless, the findings failed to achieve statistical significance. Considering the average completion time of more than 20 minutes (approximately 22 km/h), numerous questions arise regarding the time trial or the participants themselves. For most healthy individuals, it would prove challenging to maintain such a slow pace.
Conclusions Regarding Ashwagandha and Performance
Overall, the existing evidence concerning Ashwagandha's impact on strength and endurance remains dubious at best. Well-designed studies must be conducted before drawing definitive conclusions regarding the efficacy of Ashwagandha. In the meantime, supplement companies will continue to exploit studies similar to the one discussed here for marketing purposes, and individuals will persist in purchasing these supplements, hoping to improve their VO2max from 13.54 to 14.47 ml/kg/min. This seemingly negligible change in measurements equates to the distinction between an extremely slow walk and an exceedingly slow walk, all measured with impossible precision.
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Scientific references
- Sandhu JS, Shah B, Shenoy S, Chauhan S, Lavekar GS, Padhi MM. Effects of Withania somnifera (Ashwagandha) and Terminalia arjuna (Arjuna) on physical performance and cardiorespiratory endurance in healthy young adults. Int J Ayurveda Res. 2010 Jul;1(3):144-9.
- Bonilla DA, Moreno Y, Gho C, Petro JL, Odriozola-Martínez A, Kreider RB. Effects of Ashwagandha (_Withania somnifera_) on Physical Performance: Systematic Review and Bayesian Meta-Analysis. J Funct Morphol Kinesiol. 2021 Feb 11;6(1):20.
- Ziegenfuss TN, Kedia AW, Sandrock JE, Raub BJ, Kerksick CM, Lopez HL. Effects of an Aqueous Extract of _Withania somnifera_ on Strength Training Adaptations and Recovery: The STAR Trial. Nutrients. 2018 Nov 20;10(11):1807.
