Fifty one studies (n unknown) were included (36 RCTs and 15 QEDs).
Quality scores for RCTs overall ranged from 11 to 26 points, with most studies achieving high quality scores. One RCT assessing garlic and one RCT assessing guggul had a medium score. Quality scores of RCTs improved by decade (RCTs of Arjuna achieved medium scores during the 1990s and high scores during the 2000s). All QEDs had medium or high quality scores. One QED assessing guar gum and two QEDs assessing miscellaneous herbals had a medium score. The mean overall quality score for QEDs was 11.66.
Twenty one (58 per cent) RCTs had a high score for safety and tolerance assessed using the SAS-CT scale; 42 per cent of RCTs had poor safety scores. The mean score for safety and tolerance overall was 58.61 points (Arjuna=20.17, garlic=62.71, guggul=71). Most of the Arjuna studies failed to report adverse events. Safety scores did not improve by decade of publication.
Eight (57 per cent) of QEDs had high scores for safety and tolerance, six (43 per cent) had low safety scores. The mean score overall for safety and tolerance was 54 (garlic= 43.8, guggal=66.67 and guar gum=96).
Of the 28 studies that reported adverse events and tolerance, seven (25 per cent) reported no adverse events. Reported adverse events were largely gastrointestinal and transient in nature, including belching, bloating, flatulence, cramping, nausea, upset stomach and diarrhoea. Symptoms were reported for both placebo and intervention groups. Other adverse events included headaches, weakness and rashes. Few adverse events required withdrawal from the study (data not reported).
The majority of RCTs reported that treatment of hyperlipidemia with herbals was effective with 71 per cent overall reported as positive (Arjuna 100 per cent, garlic 53 per cent and guggul 86 per cent). Most QEDs reported that treatment of hyperlipidemia with herbals was effective, with 93 per cent reported as positive (garlic, guggul and guar gum reported as 100 per cent). One study evaluating silymarin had a negative outcome.