- There is some evidence from randomized clinical trials that guggul (Commiphora mukul), fenugreek (Trigonella foenum-graecum), artichoke (Cynara scolymus), yarrow (Achillea wilhelmsii), holy basil (Ocimum sanctum), red yeast (Monascus purpureus) rice, eggplant (Solanum melongena), and arjun (Terminalia arjuna) reduce serum cholesterol.
- The evidence is not conclusive for any of the products, although preliminary clinical trials seem promising; further research is warranted.
- Safety profiles from clinical trials appear encouraging, but the long-term safety has not been established; herb-drug interactions may be possible with milk thistle (Silybum marianum), Asian ginseng (Panax ginseng), guggul, and fenugreek.
- It is important for physicians to discuss the use of complementary and alternative therapies with their patients.
- Objectives To systematically review the clinical evidence for herbal medicinal products in the treatment of hypercholesterolemia.
- Study Design A systematic review of randomized clinical trials of herbal medicinal products used to lower serum cholesterol. Systematic literature searches were conducted in 6 electronic data-bases. The reference lists of all papers and our files were searched for more relevant publications. Experts in the field and manufacturers of identified herbal medicinal products were contacted for published and unpublished data. No language restrictions were imposed.
- Outcomes Measured All randomized clinical trials of serum cholesterol reduction, in which mono-preparations of herbal medicinal products were administered as supplements to human subjects, were included.
- Results Twenty-five randomized clinical trials involving 11 herbal medicinal products were identified. Guggul (Commiphora mukul), fenugreek (Trigonella foenum-graecum), red yeast rice, and artichoke (Cynara scolymus) have been most extensively studied and have demonstrated reductions in total serum cholesterol levels of between10% and 33%. The methodological quality as assessed by the Jadad score was less than 3 (maximum, 5) for 13 of the 25 trials.
- Conclusions Many herbal medicinal products have potential hypocholesterolemic activity and encouraging safety profiles. However, only a limited amount of clinical research exists to support their efficacy. Further research is warranted to establish the value of these extracts in the treatment of hypercholesterolemia.
Two recent surveys of patients undergoing cardiac surgery reported that 75% (263 of 376) and 81% (224 of 246) of patients currently use some form of complementary medicine (including herbs, vitamins, supplements, megavitamins, prayer, relaxation, spiritual healing, massage, imagery, and lifestyle and diet modifications).1,2
Many herbal medicinal products are promoted for hypercholesterolemia, including some of the top-selling supplements. It is therefore vital to establish both the efficacy of these herbal supplements in reducing serum cholesterol levels and their relative safety. This review is an attempt to systematically summarize the evidence from randomized clinical trials for the efficacy and safety of lipid-lowering herbal medicinal products.
Identification of clinical trials
To identify clinical trials involving herbal medicinal products with hypocholesterolemic properties, we conducted systematic literature searches in the following electronic databases (all from their inception to May 2001): MEDLINE (via PubMed), EMBASE, CINAHL, AMED (Alternative and Allied Medicine Database, British Library Medical Information Centre), the Cochrane Library (Issue 2, 2001), and CISCOM (Research Council for Complementary Medicine, London, UK). The search strategy is summarized in Appendix A (available online at http://www.jfponline.com).
Further relevant papers were located by hand-searching the reference lists of all papers and departmental files. In addition, experts in the field and manufacturers were contacted to provide published and unpublished material.
Inclusion and exclusion criteria
Only randomized clinical trials investigating serum cholesterol reduction of monopreparations of herbal medicinal products administered as supplements were included. These could be placebo-controlled or equivalent trials. All retrieved data including uncontrolled trials, case reports, and preclinical and observational studies were reviewed for safety data. No language restrictions were imposed.
Data extraction and quality assessment
All articles were read in full. Data relating to sample size, study design, intervention and control, treatment duration, primary outcome measures, and results were extracted by the first author and validated by the second. The methodological quality of each trial was assessed using the Jadad scoring system,3 which ranges from 0 (poorest) to 5 (highest). A score of 3 or above indicates reasonable methodological quality.
We identified 11 herbal medicinal products investigated for hypocholesterolemic properties in randomized clinical trials: guggul (Commiphora mukul), artichoke (Cynara scolymus), garlic (Allium sativum), fenugreek (Trigonella foenum- graecum), red yeast (Monascus purpureus) rice, Asian ginseng (Panax ginseng), yarrow (Achillea wilhelmsii), eggplant (Solanum melongena), holy basil (Ocimum sanctum), milk thistle (Silybum marianum), and arjun (Terminalia arjuna).
The efficacy and safety of garlic has been reviewed extensively elsewhere4–6 and is therefore not discussed in this paper. Details of all identified studies are shown in Tables 1–5 (and Table W1, available online at http://www.jfponline.com). Guggul, fenugreek, red yeast rice, and artichoke have been studied most extensively; randomized clinical trials of these herbal medicinal products with a Jadad score of 3 or above are discussed in more depth in Appendix B (available online at http://www.jfponline.com). Table 6 summarizes the adverse events experienced by subjects within these clinical trials and potential herb-drug interactions identified from systematic reviews.