Instead of evaluating the efficacy of ginseng in all patients suffering from a single disease, researchers should focus on those patients with Qi-deficiency syndrome. Qi-deficiency causes decreased visceral functions and lowered immune resistance, leading to various diseases. The manifestations of Qi-deficiency include lassitude, shortness of breath, feeble voice, dizziness, spontaneous perspiration, susceptibility to cold, pale tongue and weak pulse 10.

Chinese medicine practitioners prescribe herbal medications to rectify disharmony in a patient's system 16. Healthy individuals should not participate in treatment groups in Chinese medicine studies. This explains the negative results from the ginseng studies in which healthy individuals participated 1718192021.

Ginseng is a Qi-tonifying herb to treat five major syndromes 16 caused by Qi-deficiency. Therefore, we argue that only studies in which participants are diagnosed with Qi-deficiency are valid to evaluate ginseng's efficacy 22232425.

While at least eight species of ginseng are commercially available 26, only two major species, namely Panax ginseng (Chinese or Korean ginseng) and Panax quinquefolius (American ginseng), are used as medicinal herbs worldwide. According to Chinese medicine theory, the properties and functions of these two species are quite different 16. While P. ginseng enhances Yang, P. quinquefolius nourishes Yin. A search for randomized controlled trials of ginseng in PubMed (7 September 2008) found that about one-third of the studies did not mention the ginseng species used and that very few studies addressed the species issue.

Herbal quality may affect research results. Different batches of P. ginseng 2728 or P. quinquefolius 29 produced opposing study results respectively on acute postprandial glycemia. The primary active ingredients in ginseng are ginsenosides. G115, a ginsenoside-based standardized extract of P. ginseng, may help assess the efficacy and safety of ginseng. In fact, G115 was used in most P. ginseng (single herb) trials reviewed in this paper.

In Chinese medicine, herbs are often formulated to achieve increased therapeutic effects and reduced toxicity or side effects 16. Results from clinical trials on herbal formulae confirm this practice. A Japanese trial found that a 7-herb formula was effective in preventing liver cancer in cirrhosis patients 30. Two British trials showed that a 10-herb formula was effective in treating a severe atopic eczema 3132. No single herbal ingredient explains the efficacy in these studies 33. Furthermore, ginseng herbal formulae were shown to be effective in treating chronic pulmonary disease 2234, congenital heart disease 3536, mild cognitive impairment 37, coronary heart disease 38 and nasopharyngeal carcinoma 39.

Certain Chinese medicine herbs are toxic and others may have adverse effects when used improperly 16. A condition known as the ginseng abuse syndrome is characterized by heart palpitations, heaviness in the chest, high blood pressure, dizziness, insomnia, agitation, restlessness, nausea, vomiting, abdominal pain and/or bloating, diarrhea, possible upper digestive tract bleeding, edema, and red skin rash 40. Most of these reported adverse effects are common manifestations of Qi-excess and Qi-stasis. While all clinical trials should document adverse effects, only one trial did do so 41.

Out of the 19 trials, nine had negative results, ten had positive results, and none targeted ginseng's efficacy on Qi-deficiency syndromes.

Both healthy and unhealthy participants were evaluated for the effects of ginseng. Seven out of the nine trials with negative results involved healthy participants, whereas eight out of the ten studies with positive results had participants with Qi-deficiency manifested by cancer, impotence and pulmonary disease. Ellis et al. 48 investigated the time-dependent effects of P. ginseng on the quality of life in a healthy young adult population. In this case, the participants had marginal Qi-deficiency as young adults are at the stage of 'gradual filling of Qi and Xue' 9 according to Chinese medicine theory.

The species of ginseng may be a confounding factor in the interpretation of trial results, which is illustrated by four trials as follows (Table 1).

Stavro et al. 40 enrolled 52 hypertensive participants to evaluate the long-term effects of P. quinquefolius on blood pressure 49. Long-term use of ginseng was reported to be associated with the development of hypertension, which was refuted by Stavro et al. In Chinese medicine practice, however, P. quinquefolius, unlike its cousin P. ginseng, is in fact used to treat hypertension in some cases.

Wiklund et al. 50 reported a trial in which 384 symptomatic postmenopausal women were assessed for the effects of P. ginseng on the quality of life and physiological parameters. Postmenopausal symptoms such as hot flashes are often regarded as Shen (kidney) Yin-deficiency 51 and are treated with P. quinquefolius rather than P. ginseng. Moreover, the use of P. ginseng in this study was contraindicated and might have produced adverse effects.

Cicero et al. 52 studied 20 elderly hypertensive and digitalized patients treated with Acanthopanax senticosus (Siberian ginseng) which is a mild Qi-tonic for an unspecific feeling of fatigue, a sign of Qi-deficiency 53. Hypertension is manifested in five syndromes 11, of which Qi-deficiency is only a minor one. The positive results from this trial were due to the fact that A. senticosus, an alternative Qi-tonic, was used 16.

Liang et al. 54 found that P. notoginseng improved endurance time to exhaustion and lowered mean blood pressure in 29 untrained young adults during an endurance exercise. P. notoginseng is another important ginseng species classified as homeostatic medicine to arrest bleeding and removes stagnant Xue.