Guggul (Commiphora mukul)
Six randomized clinical trials of guggul, involving 388 patients with different diagnoses, were identified.7-12 Five were conducted in India and 1 in the United States; 4 were placebo-controlled; and 1 compared guggul with 2 reference compounds. The results suggest reductions in total serum cholesterol from 10% to 27% compared with baseline levels (Tables 1 and W1).
High-density lipoprotein (HDL) cholesterol levels were measured in 3 of the studies.7- 9 A significant increase was seen after 8 weeks of treatment in 1 study9; in the others, no significant differences were seen.7,8 A statistically significant decrease in lipid peroxide levels was reported in 1 study, with no corresponding change in the placebo-treated group.7
Several mild adverse events were reported during these trials, including rash, nausea, vomiting, eructation, hiccup, headache, loose stools, restlessness, and apprehension, although information regarding adverse events experienced during placebo administration was not always provided. A potential drug interaction with propranolol and diltiazem was investigated in a randomized crossover trial of 17 healthy volunteers, in which guggul was found to significantly reduce the peak plasma concentration of both drugs.13
Fenugreek (Trigonella foenum-graecum)
Fenugreek seeds. Five randomized clinical trials were identified, involving 140 patients; all but 1 trial was conducted in India.14-17 Although the methodological quality of the studies was considered generally poor in 4 of the trials, statistically significant reductions in total serum cholesterol of between 15% and 33% compared with baseline were demonstrated (Table 2).
Fenugreek leaves. In a single-blind study of 20 healthy male volunteers, Abdel-Barry and colleagues found a nonsignificant decrease of 9% in total serum cholesterol after a single dose of an aqueous extract made from fenugreek leaves (40 mg/kg) compared with a reduction of 2.8% after dilute coffee extract (placebo) (Table 2). 18
Within all the identified studies of fenugreek, patients reported mild gastrointestinal symptoms such as increased flatulence, nausea, fullness, and diarrhea during fenugreek treatment, but none was severe enough to necessitate withdrawal from the study. A 14% reduction in serum potassium was noted in healthy volunteers after a single dose of an aqueous extract of fenugreek leaves. 18
Red yeast rice
Red yeast rice is produced by solid-state fermentation of washed and cooked rice using the fungus Monascus purpureus. It has been used in Asia as a food preservative and colorant and for its medicinal properties since the Tang Dynasty (ad 800). It is available in capsules that contain a pulverized powder of fermented rice and yeast.
Four randomized clinical trials of the lipid-lowering effects of red yeast rice conducted in patients (n=695) with hyperlipidemia were identified (Table 3).19-22 In all studies, statistically significant reductions (16% to 31%) in total serum cholesterol compared with placebo or control or baseline were seen.
Adverse events experienced in clinical trials included stomachache, heartburn, dizziness, and flatulence. No changes in liver function tests were demonstrated. There was 1 case report of a 26-year-old man who used red yeast rice in preparing sausages and developed anaphylaxis due to immediate sensitivity to M purpureus.23 Whether this is relevant to the oral administration of red yeast rice capsules is not clear.
Artichoke (Cynara scolymus)
The choleretic effect of the leaf extract of artichoke has been studied widely, but only 2 randomized clinical trials of its hypocholesterolemic effects, involving 187 patients, were identified (Table 4).24,25 One trial (n=44 healthy volunteers), published in abstract form only, found no significant difference in lipid levels compared with placebo, although post hoc subanalyses revealed some reductions in total serum cholesterol in patients with baseline levels above 5.4 mmol/L; these results should be interpreted with some caution. Reductions in total cholesterol of 18.5% and 8.6% were reported in the other, larger trial after artichoke and placebo treatments, respectively.
No adverse events were reported during either study. Three post-marketing surveillance studies were located: one included 417 patients and reported excellent tolerability in 95%; in the second (203 patients) no adverse reactions were reported; and the third (553 patients) described mild adverse events in 1.3% of patients (flatulence, hunger, and weakness).24-28
Discussion
Many different herbal medicinal products have been identified with potential lipid-lowering properties (Table 5), but the evidence for each herb is limited. The largest amount of published literature exists for guggul, fenugreek, red yeast rice, and artichoke, with reductions in total serum cholesterol ranging from 10% to 33%.
Although HDL and low-density lipoprotein (LDL) cholesterol were not measured in all the studies, increases in HDL and decreases in LDL levels were seen with guggul, red yeast rice, and yarrow, and decreases in LDL levels were seen in studies of fenugreek, arjun, and artichoke.