Ginseng is the collective term used to describe several species of plants belonging to the genus Panax. These include the Asian ginsengs (Panax ginseng and Panax japonicus), which have been used medicinally for more than 2000 years in China, Japan and Korea. American gin-seng (Panax quinquefolius L) grows in North America and much of it is exported to the Far East. Siberian/Russian ginseng (Eleuthrococcus senticosus) is not considered to be true ginseng because it is not a species of the genus Panax. However, as a supplement, it is often promoted alongside Asian and American ginseng products.
Panax ginseng contains complex mixtures of saponins known as ginsenosides, which are found in the roots. At least 20 saponins have been isolated from ginseng roots. However, species vary in composition and concentration, and varying concentrations of different saponins appear to exert opposite pharmacological effects.1,2 This may explain the conflicting results reported in clinical studies, although issues such as type of ginseng, time of harvest, storage and lack of standardisation of active ingredients may also be important. Eleuthero-sides are believed to be the active ingredients in Siberian ginseng, but these have different chemical structures than the ginsenosides.
Ginseng has a wide range of pharmacological effects, but its clinical significance in humans has not been fully investigated. Differences in composition of the different species lead to differences in activity.
Analgesic activity, anti-pyretic activity, anti-inflammatory activity, CNS-stimulating and CNS-depressant activity, hypotensive and hypertensive activity, histamine-like activity and antihistamine activity, hypoglycaemic activity and erythropoietic activity have all been reported.2 Opposing activities such as hypertension and hypotension are thought to be a result of different ginsenosides in one preparation.
The most consistent biochemical explanation for the effects of the ginsenosides is a facilitating influence on the hypothalamic-pituitary-adrenal axis.3,4 Interactions with central cholinergic5 and dopaminergic mechanisms6 have also been demonstrated.
Ginseng is an ancient remedy that has been used for thousands of years in the East. A number of extravagant claims have been made for it, including aphrodisiac and anti-ageing properties. It is not claimed to cure any specific disease, but to restore general vitality. Ginseng is claimed to be useful for:
alleviating symptoms of tiredness and exhaustion;
amnesia and mental function;
improving libido and sexual vigour and preventing impotence;
regulating blood pressure;
preventing diabetes mellitus;
preventing signs of old age and extending youth;
improving immunity; and
reducing the risk of cancer.
Available evidence for some of these claims has come mainly from animal studies, including: increased adaptability to stress;7 increasing stamina;8 decreasing learning time;9 reduction in blood pressure;10 anti-inflammatory activity;11 and improved sleep.12
Ginseng has been suggested to influence cardiovascular function. One double-blind RCT in healthy adults investigated the potential influence of Panax ginseng on electrocardiographic parameters: PR, QRS, QT, QTc and intervals, and QT and QTc interval dispersion. Effects on blood pressure and heart rate were also evaluated. Thirty subjects were randomly allocated to receive 28 days of therapy with Panax ginseng 200 mg or placebo. Panax ginseng was found to significantly increase the QTc interval and decrease diastolic blood pressure 2 h after ingestion on the first day of therapy.13
North American ginseng has been evaluated for its effect on blood pressure. Sixteen individuals with hypertension were randomised to receive placebo treatment on two mornings or powdered North American ginseng on six mornings. After treatment, blood pressure was measured every 10 min for 160 min, and the mean obtained for the overall 160-min period. None of the North American ginsengs or their means differed from placebo in their overall effect on mean blood pressure change. None affected blood pressure versus placebo at 10-min intervals, but their mean versus placebo increased systolic and diastolic blood pressure at 100 min. The authors concluded that these findings together suggested that North American ginseng exerts a neutral acute effect on blood pressure in hypertensive individuals.14
A further study in 24 children undergoing heart surgery found that a ginsenosides com-pound injected intravenously may attenuate gastrointestinal mucosal injury and inhibit the systemic inflammatory response that occurs after cardiopulmonary bypass in patients with congenital heart disease.15
A systematic review of 34 studies investigating the influence of ginseng on blood pressure, lipids and/or blood glucose found mixed results, with current evidence not supporting the use of ginseng to treat cardiovascular risk factors. Some studies suggest a small reduction in blood pressure and some that ginseng improves blood lipid profiles and lowers blood glucose. However, the authors concluded that the overall picture is inconsistent and well-designed RCTs are lacking.16 A recent 12-week RCT found that American ginseng had no effect on 24-h blood pressure.17
In an uncontrolled study in humans, ginseng has been shown to increase stamina in athletes and concentration in radio operators.18 In a double-blind, placebo-controlled trial, 60 elderly patients received a supplement containing Panax ginseng and vitamins and minerals or placebo daily for 8 weeks. There was no difference in the ability of the supplement or placebo to influence the rehabilitation of these patients, and the effects of the ginseng could not be separated from the other ingredients in the product.19
A more recent trial, in 30 healthy young adults given ginseng G115 200 mg, ginseng G115 400 mg or placebo, found notable behavioural effects during sustained mental activity, particularly with 200 mg ginseng. These included significantly improved subtraction task performance and significantly reduced mental fatigue. Both the ginseng treatments led to significant reductions in blood glucose levels and the authors suggested that the effects on mental performance may be related to the acute gluco-regulatory properties of the extract.20
Studies have also investigated the cognitive effects of Panax ginseng and ginkgo biloba in combination. In a trial involving 20 healthy young adults, receiving 320, 640 and 960 mg of the combination, the most striking result was a dose-dependent improvement in performance on the ‘quality of memory’ factor at the highest dose of the combination (960 mg).
Further analysis revealed that this effect was differentially targeted at the secondary memory rather than the working memory component. There was also a dose-dependent decrement in performance of the ‘speed of attention’ factor for both the 320 and 640 mg doses.21
A further trial by this same group investigated the influence of ginkgo 360 mg, ginseng 400 mg, 960 mg of a ginseng/ginkgo combination and a matching placebo on both mood and cognition. All three treatments were associated with improved secondary memory performance, with the ginseng treatment showing some improvement in the speed of performing memory tasks and in the accuracy of attentional tasks. Following the combination, there was improvement in some mental arithmetic tasks. No modulation of the speed of performing attention tasks was evident. Improvements in self-rated mood were also found following ginkgo and to a lesser extent the combination product.22
A small preliminary study23 showed that American ginseng reduced blood sugar levels both in people who had diabetes mellitus and in healthy subjects. However, because the study looked only at a single time point, it is unclear what the results mean for real meals or prevention and treatment of diabetes. But the research suggests that ginseng may be useful in preventing sharp increases in blood sugar. A further study in 10 patients with type 2 diabetes showed that American ginseng reduced post-prandial glycaemia, and that no more than 3 g was required to achieve reductions.24
A double-blind, placebo-controlled study in 36 patients with type 2 diabetes showed that ginseng therapy (100 and 200 mg) significantly reduced fasting blood glucose and elevated mood, and the 200-mg dose resulted in a statistically significant improvement in glycated haemoglobin.25
Further trials have shown variable effects on blood glucose, possibly because of the variety and concentration of ginsenosides in the preparations tested. One trial showed that American ginseng reduced post-prandial glycaemia in subjects without diabetes. This reduction was time-dependent, but not dose-dependent. An effect was seen only when the ginseng was administered 40 min before the challenge. Doses within the range 1–3 g were equally effective.26 Another trial found that American ginseng 6 g daily did not reduce post-prandial glycaemia. The authors suggested that a possible explanation for this was the reduced total ginsenosides in the product, indicating that the ginsenoside profile of American ginseng might play a role in its hypoglycaemic effects.27
A further study with Asian ginseng found both null and opposing effects on indices of acute post-prandial plasma glucose and insulin, with the authors concluding that this could be explained by the marked ginsenoside differences in the product.28 The same research group went on to look at the effects of eight popular types of ginseng on acute post-prandial glycaemic indices in healthy humans to find again that there was some variability. They concluded that the ginsenoside content might be involved but that other components might also have an effect.29
Case-control30 and cohort31 studies in Korean subjects have shown that incidence of cancer is lower in those who consume ginseng than in those who do not.
A placebo-controlled (not blinded study) included 90 patients with erectile dysfunction.32 They were randomly assigned to receive Panax ginseng (300 mg daily), trazodone or placebo. Patient satisfaction, libido and penile rigidity and girth were greater in the ginseng group than in the other two groups, but changes in the frequency of intercourse, premature ejaculation and morning erections were not found in any group. None of the treatments resulted in complete remission of erectile dysfunction.
Korean ginseng has been investigated for a role in erectile dysfunction. A total of 45 patients with diagnosed erectile dysfunction were enrolled in a double-blind, placebo-controlled, crossover study in which the effects of Korean red ginseng (900 mg three times a day) were compared with placebo. Mean International Index of Erectile Function scores and scores on penetration and maintenance were significantly higher in patients treated with Korean red ginseng. Penile tip rigidity also showed significant improvement for ginseng versus placebo. The authors concluded that Korean red ginseng can be an effective alternative for treating male erectile dysfunction.33
Several human studies have shown an ergogenic effect in exercise, but a review concluded that such trials have been poorly controlled and not blinded, and that there is no compelling evidence that ginseng improves exercise performance in humans.34 Double-blind, placebo-controlled trials do not support an ergogenic effect of ginseng on exercise performance,35–38 or on the response of anabolic hormones (growth hormone, testosterone, cortisol, insulin-like growth factor 1) following resistance status.39
A double-blind RCT in 38 active healthy adults investigated the effect of 400 mg daily of G115 (equivalent to 2 g of Panax ginseng) on secretory IgA, performance and recovery after interval exercise. There was no significant change in secretory IgA (an indicator of mucosal immunity). Supplementation with ginseng failed to improve physical performance and heart rate recovery of individuals undergoing repeated bouts of exhausting exercise.40
A trial with Panax notoginseng found that a dose of 1350 mg daily for 30 days improved endurance time to exhaustion by 7 min and lowered mean blood pressure (from 113 ± 12 to 109 ± 14 mmHg) and VO2 at the 24th minute (from 32.5 ± 8 to 27.6 ± 8) during endurance cycle exercise.41 A trial in 13 physically active male students found that supplementation with American ginseng for 4 weeks prior to exhaus-tive aerobic treadmill running did not enhance aerobic work capacity but significantly reduced plasma creatine kinase during the exercise. The authors concluded that the reduction in plasma creatine kinase may be due to the fact that American ginseng is effective in decreasing skeletal muscle cell membrane damage, induced by exercise during the high-intensity treadmill run.42
Upper respiratory tract infections
Two recent trials have investigated the potential benefit of ginseng in preventing upper respiratory tract infection. In one trial, American ginseng over 8 or 12 weeks was found to be safe, well tolerated and potentially effective in preventing acute respiratory illness caused by influenza and respiratory syncytial virus (RSC).43 A further trial with American ginseng in 323 subjects aged 18–65 years found that supplementation for 4 months reduced the mean number of colds per person, the proportion of subjects who experienced two or more colds, the severity of symptoms and the number of days on which cold symptoms were reported.44
Quality of life
Both Panax ginseng and Siberian ginseng have been found to improve aspects of mental health and social functioning after 4 weeks of therapy, although these benefits attenuate with continued use.45,46 In another study, Panax ginseng had no influence on mood or affect.47 Siberian ginseng has been shown to have potential efficacy for patients with moderate fatigue.48
Ginseng should be avoided by children and used with caution by patients with CVD (including hypertension), diabetes mellitus, asthma, schizophrenia and other disorders of the nervous system. Because of a possible effect on blood glucose, the effect of ginseng on glucose measurement in diabetes should be borne in mind.
Pregnancy and breast-feeding
Ginseng should be avoided.
Ginseng is relatively non-toxic, but in high doses (>3 g ginseng root daily) can give rise to the following symptoms: insomnia, nervous excitation, euphoria; nausea and diarrhoea (especially in the morning); skin eruptions; oedema; oestrogenic effects (e.g. breast tenderness; temporary return of menstruation in post-menopausal women).50,51
A systematic review of the adverse effects and drug interactions of Panax ginseng concluded that the incidence of adverse effects with ginseng monopreparations is similar to that with placebo. The most commonly experienced adverse events are headache, sleep and gastrointestinal disorders. The possibility of more serious adverse events is indicated in isolated case reports and data from reporting schemes. However, causality is often difficult to determine from the evidence provided. Combination products containing ginseng as one of several constituents have been associated with serious adverse events and even fatalities. Possible interactions include ginseng and warfarin and ginseng and phenelzine.52
Tranquillisers: ginseng may reverse the effects of sedatives and tranquillisers.
Digoxin: ginseng may increase blood levels of digoxin.53
Warfarin: ginseng may influence the effect of warfarin.54–57
Ginseng is available in the form of tablets, capsules, teas, powders and tinctures. Red ginseng is derived from steam-treated ginseng roots and white ginseng from air-dried roots. Surveys have found that the ginsenoside concentrations in different products vary enormously.1,58 A review of 21 US products found that seven had less than the required concentration of ginsenosides, two products contained lead above acceptable levels and eight contained unacceptable levels of quintozene and hexachlorobenzene.59
The dose is not established. Manufacturers tend to recommend 0.5–3 g daily of the dried root or its equivalent.
Ginseng has been used for thousands of years, but there are few controlled trials in humans. Many studies have produced conflicting results, perhaps due to lack of standardised products, variation in dosage, differences in harvest conditions of the plants and types of ginseng used. A 1999 systematic review49 concluded that evidence for the efficacy of ginseng for any indication is weak. The review investigated the effect of ginseng on athletic performance, psychomotor and cognitive performance, immunomodulation, diabetes mellitus and herpes. Ginseng is taken for a range of other indications but there is little evidence that ginseng slows the ageing process, helps mental or physical functioning in the elderly, increases exercise performance or improves sexual function.
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