A systematic review 1 including 34 studies (22 RCTs and 12 non-randomised studies, NRSs) with a total of 1 719 subjects was abstracted in DARE. Patients with different chronic conditions and healthy individuals were included, and the duration of the intervention ranged from a single dose to 27 months. Out of 8 multiple-dose studies (6 RCTs, 2 NRSs) on blood pressure, 2 RCTs found a significant reduction in blood-pressure compared with placebo. One of these found a significant reduction in systolic blood-pressure (4%) in patients with type 2 diabetes mellitus compared with placebo, while the other found a significant reduction in diastolic blood-pressure (3%) in patients with physical or emotional stress compared with the control group. Three studies demonstrated slight elevations in blood-pressure (1 to 4%), two compared with placebo and one compared with baseline, but these were not statistically significant. Out of 3 single-dose studies (1 RCT, 3 NRSs), 2 acute single-dose studies (1 RCT, 1 NRS) found greater reductions in systolic and diastolic blood-pressure (8 to 11%). When the participants in one of these studies were examined in a subsequent RCT with placebo control, a much smaller reduction was shown (1 to 4%).
9 studies (3 RCTs and 6 NRSs) examined the effect of ginseng products on lipid levels. Overall, the results were inconsistent. Five studies found a statistically significant improvement in one or more lipid parameters compared with baseline or an active control group.
There were 9 single-dose studies (all RCTs) on blood glucose; one research group performed all of them. 5 studies conducted with Panax quinquefolius found reductions in postprandial blood glucose levels (9 to 39%) in patients with and without diabetes. 3 acute studies conducted with Panax ginseng found either no change in postprandial blood glucose or an increase in postprandial blood glucose levels. Out of 6 multiple-dose studies (4 RCTs, 2 NRSs), 4 studies found significant reductions in blood glucose outcomes compared with placebo. Reductions of 7 to 10% in fasting blood pressure (3 studies), 4 to 8% in glycosylated haemoglobin (2 studies) and 13% in blood glucose (1 study) were observed. No other statistically significant between-group differences were found.
Comment: The quality of evidence is downgraded by study quality (most studies were considered to be of poor quality), by inconsistency (variability in results across studies) and by indirectness (the majority of studies were short term).
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