Efficacy of Ginseng Supplements on Fatigue and Physical Performance: a Meta-analysis

Fatigue, which is a lack of energy and motivation, can be a normal and important response to physical activity, emotional stress, boredom, or lack of sleep (1). For the purpose of relieving fatigue, other than conventional medical treatments, approximately 80% of people with chronic fatigue use alternative and complementary therapies such as massage or herbal supplements in the United States (2).

Physical performance relates to the ability to complete certain physical tasks with higher intensity, faster, or with a higher power output (3). In general, the various ginseng supplements currently available in market are claimed to increase energy levels, relieve stress, enhance athletic performance and immune system functions, control blood sugar levels, improve mental functions, and promote general well-being.

According to a review, Panax ginseng, the most attractive product of the ginseng markets in South Korea, accounts for approximately 59% in the entire Korean market, and its consumption has continuously risen (4). Extracts of P. ginseng C.A. Meyer, more commonly known as Chinese or Korean Ginseng, have a long history of use in traditional medicine in several Asian countries (5). They also have become readily accepted in many Western countries where people often consume these preparations, expecting that they may offer relief and protection in the fight against stress, disease, and fatigue (5, 6). The wide spread use of ginseng had led researchers to assess its efficacy as therapeutic and ergogenic nutritional supplements for combating fatigue and enhancing physical performance (7).

There are two major species of ginseng, Korean ginseng (P. ginseng) and American ginseng (P. quinquefolius) with various amounts and ingredients. They mainly includes ginsenosides, which are the most important ingredients (8). To date, numerous active compounds (including approximately 40 ginsenosides) have been identified in P. ginseng with various pharmacological activities, such as effects on chemical stress, immune modulation in animal studies, antitumor activities, as well as glucose metabolism and enhancement of cognitive performance (9, 10, 11). However, those effects are not clinically established.

To date, several randomized controlled trials (RCTs) have reported the efficacy of ginseng supplements on fatigue reduction (12, 13, 14, 15) and physical performance enhancement (16, 17, 18, 19, 20, 21, 22, 23). However, those findings remain inconsistent. Also, no meta-analysis has been published on this topic, so far.

This study aimed to investigate the efficacy of ginseng supplements on fatigue relief and physical performance enhancement by using a meta-analysis of RCTs.

In this meta-analysis of RCTs, we found that the use of ginseng supplements had the efficacy on fatigue reduction, but not physical performance enhancement. Specifically, the effect size on the efficacy of ginseng supplements on fatigue reduction (SMD = 0.34) was between the small (SMD = 0.20) and medium levels (SMD = 0.50) based on Cohen’s rule of thumb (27). However, we found that only four relevant RCTs have been published regarding fatigue reduction, and the total number of the study participants included in those trials was only 429. Thus, there was no sufficient clinical evidence to support the use of ginseng supplements on reducing fatigue and enhancing physical performance.

There are some possible biological mechanisms for the efficacy of ginseng supplements on mental and physical fatigue reduction and physical performance enhancement. Regarding mental fatigue, although a human study indicated that ginseng increases cognitive performance (28), its mechanisms remain not known, but may be related to the ginseng's glycemic properties (29, 30). Ginseng affects brain activity, specifically by increasing cortical levels of dopamine, noradrenalin, serotonin, and cyclic adenosine monophosphate (cAMP) (31). An in vitro study suggested that ginseng increases energy produced aerobically in the brain (32). Ginseng saponins showed moderate depressant actions on the electroencephalogram and the behavior in cats (33). As for physical fatigue and physical performance, ergogenic aids are believed to increase performance by some of the following mechanisms: renewing or increasing energy stores in the body, facilitating the biochemical reactions that yield energy, reducing or neutralizing performance-inhibiting metabolic by products, and facilitating recovery (34, 35). Although the mechanism on the ergogenicity of ginseng on physical performance has not been fully identified, theories include stimulation of the hypothalamic-pituitary-adrenal cortex axis and increased resistance to the stress of exercise, enhanced myocardial metabolism, increased hemoglobin levels, vasodilatation, increased oxygen extraction by muscles, and improved mitochondrial metabolism in the muscle, all of which theoretically could enhance physical performance (36, 37, 38, 39). A clinical experimental study reported that the use of ginseng supplements before exhaustive aerobic exercise can reduce creatine kinase leakage during exercise, possibly due to ginseng's ability to reduce cellular and muscle damage (40).

However, although there are some possible biological mechanisms on the efficacy of ginseng supplements on physical performance enhancement in in vivo animal or in vitro laboratory studies, our meta–analysis of eight randomized controlled trials found that there was no sufficient evidence on the efficacy. Several explanations could be considered for this inconsistence. First, preclinical studies, including in vivo laboratory studies and animal studies might not represent the biological mechanism in the human body. Therefore, although preclinical studies showed an efficacy of ginseng supplements on physical performance enhancement, clinical circumstances could report no benefit of ginseng supplements. Second, the sample size of the final meta-analysis is a limitation to evaluate the efficacy. We only included eight RCTs with 212 participants due to a paucity of data. Third, there was heterogeneity in the participants in each trial. While two American studies including 39 participants were conducted in healthy adult females (16, 19), American (17) and Thailand (22) studies including 88 participants were conducted in health adult males. Finally, the dose and duration of the intervention in each trial varied from 350 mg/day/person to 3,000 mg/day/person and 4 weeks to 8 weeks among included studies.

We have limitations in the current meta-analysis. Although we found that there was a significant efficacy of ginseng supplements on fatigue reduction, no sufficient RCTs were published in order to confirm this finding. The number of the study participants was not enough to draw conclusions. Specifically, out of a total of 429 study participants from all four RCTs, 271 participants were from Barton’s study (13), which indicated a significant efficacy. Also, many RCTs were excluded from the final analysis because of insufficient data.

To the best of our knowledge, this meta-analysis is thought to be the first meta-analysis of RCTs about this issue. Although there is no sufficient clinical evidence about the efficacy of ginseng supplements for health, in some countries, especially Korea, some sellers promote the sale of ginseng supplements as if these are clinically approved effective against fatigue or some diseases, and also many people have consumed ginseng supplements in the belief that these prevent diseases and improve their health.

In summary, we found that there was insufficient clinical evidence to support the use of ginseng supplements on reducing fatigue and enhancing physical performance because only a few RCTs with a small sample size were published so far. Further lager RCTs are needed to confirm the efficacy of ginseng supplements for fatigue reduction and physical performance enhancement.