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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Herbs for serum cholesterol reduction: a systematic review

JS Thompson Coon and E Ernst.

Review published: 2003.

CRD summary

This review assessed whether herbal medicines can reduce cholesterol. There was limited evidence to suggest that the herbal medicines assessed might lower cholesterol. Further research is warranted to establish the therapeutic value of these herbs in the treatment of hypercholesterolaemia. The authors' cautious conclusions seem consistent with the poor quality evidence presented.

Authors' objectives

To review systematically the evidence from randomised clinical trials (RCTs) for the efficacy and safety of lipid-lowering herbal medicinal products.

Searching

MEDLINE, EMBASE, CINAHL, AMED, the Cochrane Library (Issue 2, 2001) and CISCOM were searched from their inception to May 2001. Departmental files and the reference lists of identified papers were checked, and experts and manufacturers were contacted. No language restrictions were applied.

Study selection

Study designs of evaluations included in the review

Only RCTs were included for efficacy. All the retrieved data, including uncontrolled trials, case reports and preclinical and observational studies, were reviewed for safety data.

Specific interventions included in the review

The inclusion criteria specified monopreparations of herbal medicinal products with hypocholesterolaemic properties, administered as supplements. The specific interventions in the included studies were: guggul, fenugreek seeds, fenugreek leaves, red yeast rice, artichoke, eggplant, arjun, Asian ginseng, holy basil, yarrow, silymarin. Studies using garlic were not included. Some studies included concomitant low-fat or low-cholesterol diets. The comparison groups varied both within herbal medications and between medications. The comparison groups were active treatments, placebo or 'control'. Brief details of the comparators were given in the paper. The length of treatment ranged from a single dose to 24 weeks.

Participants included in the review

The inclusion criteria for the participants in the review were not specified. The participants included healthy volunteers and those diagnosed variously with hypercholesterolaemia, hyperlipidaemia, coronary artery disease, non insulin-dependent diabetes mellitus, dyslipidaemia, human immunodeficiency virus-related dyslipidaemia, and obesity. No further details were given.

Outcomes assessed in the review

The inclusion criteria were not specified in terms of the outcomes of interest. Those reported were changes in total cholesterol (TC), high-density lipoprotein cholesterol and low-density lipoprotein cholesterol. Safety and adverse effects were also discussed.

How were decisions on the relevance of primary studies made?

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

Assessment of study quality

The methodological quality of the trials was assessed using the Jadad scale. On the scale of 0 (poorest) to 5 (highest), a trial with a score of at least 3 was considered to be of reasonable quality. No trials were excluded on the grounds of a poor quality score. The authors did not state how the papers were assessed for quality, or how many reviewers performed the quality assessment.

Data extraction

The data were extracted by one author and validated by a second. Data relating to the sample size, study design, intervention and control, treatment duration, primary outcome measure, and results were extracted. Changes in lipid levels from baseline were given for each lipid level measured. It was stated that data from the original studies, as well as additional tables and graphs, are available on the Journal of Family Practice website; it should be noted that free access to full text is available to subscribers only.

Methods of synthesis

How were the studies combined?

The results were discussed as a narrative synthesis grouped by individual herbs. The percentage reductions in total serum cholesterol for all herbal products considered together were given. The results for safety were given for individual studies.

How were differences between studies investigated?

For efficacy, the studies were discussed according to the herbal medicinal product.

Results of the review

Twenty-five RCTs (n=1817) involving 11 herbal medicinal products were identified. Six RCTs (n=388) involved guggul; 5 RCTs (n=140) used fenugreek seeds; 1 RCT (n=20) used fenugreek leaves; 4 RCTs (n=773) used red yeast rice; 2 RCTs (n=183) used artichoke; 7 RCTs (313) used other herbs. However, there seemed to be a discrepancy in the numbers of participants tabulated in the paper compared with those given online.

Thirteen of the 25 RCTs were assessed to be of low methodological quality with a score of below 3. The reductions in total serum cholesterol ranged from 10 to 33% for all herbs considered together; the main results for the individual herbs were also given.

Guggul: the 5 studies that measured TC found reductions of 10 to 27% in comparison with baseline measures.

Fenugreek: statistically-significant reductions in TC of between 15 and 33% were demonstrated for fenugreek seeds (5 studies). The single study of fenugreek leaves found a non significant reduction of 9% in TC after a single dose, compared with a reduction of 2.8% with placebo (dilute coffee extract).

Red yeast rice (4 studies): there were statistically-significant reductions in TC of 16 to 31%, compared with placebo or control or baseline.

Artichoke (2 studies): one study showed reductions in TC of 18.5% and 8.6% for artichoke and placebo, respectively. The other study found no significant difference in lipid levels in comparison with placebo, although subgroup analyses showed reductions in some groups of participants.

Other herbs: eggplant, arjun, Asian ginseng, holy basil, yarrow and silymarin. Of the 2 studies of eggplant, one showed a reduction in TC of 6.8% from baseline while the other showed an increase of 23%. The study using arjun showed a reduction in TC from baseline of 9.7%. Neither of the 2 studies using Asian ginseng showed any change from baseline, while for holy basil the reduction was 7.6% and for yarrow it was 39%. For silymarin there was a 2.6% increase in TC from baseline.

In terms of safety, mild adverse events were described for all of the herbs and there was the possibility of some drug interactions with guggul, fenugreek, Asian ginseng and silymarin (full details provided in the paper).

Authors' conclusions

There was limited evidence to support the 11 herbal medicinal products with potential hypocholesterolaemic activity that were identified. In addition to lowering cholesterol, several of the herbs may exert beneficial effects in cardiovascular disease by elevating high-density lipoprotein levels and inhibiting lipid oxidation. While the long-term safety of these products has not been established, the safety profiles seem encouraging.

CRD commentary

This was a review of an alternative group of compounds, in which the aims were clearly stated and the search appears to have been comprehensive. However, there were inconsistencies between the tables in the paper and those online, in terms of the numbers of participants. There was also some inconsistency in the naming of herbs: some tables referred to silymarin while others used the term milk thistle. It is assumed that salymarin is milk thistle. The authors acknowledged that there were several shortcomings to the review, including possible publication and language bias, since much research has been conducted in India and China. In addition, although over half the retrieved RCTs were of poor methodological quality, they were all included and no sensitivity analysis was performed using only the trials of adequate quality. However, detailed descriptions of this latter group are given on the Journal of Family Practice website. The narrative analysis of individual herbs dealt with heterogeneity of the included compounds. For completeness, an overall result for all herbs considered together was presented. Overall, the cautious conclusions seem consistent with the evidence presented.

Another publication by the same authors, which reached the same conclusions, reported data from an additional 12 non-randomised studies (see Other Publications of Related Interest).

Implications of the review for practice and research

Practice: The authors stated that it would be prudent for physicians to explore the use of herbal medicinal products with potential lipid-lowering properties in their clinical decision-making.

Research: The authors stated that further research is warranted to establish the therapeutic value of these herbs in the treatment of hypercholesterolaemia.

Bibliographic details

Thompson Coon J S, Ernst E. Herbs for serum cholesterol reduction: a systematic review. Journal of Family Practice 2003; 52(6): 468-478. [PubMed: 12791229]

Other publications of related interest

Thompson Coon J, Ernst E. Herbal medicinal products for the treatment of hypercholesterolemia: a systematic review. Perfusion 2003;16:40-55.

Indexing Status

Subject indexing assigned by NLM

MeSH

Cholesterol /blood; Drug Interactions; Evidence-Based Medicine; Herbal Medicine /methods /standards; Humans; Hypercholesterolemia /blood /drug therapy; Patient Education as Topic; Phytotherapy /methods /standards; Randomized Controlled Trials as Topic; Research Design /standards; Treatment Outcome

AccessionNumber

12003009681

Database entry date

30/04/2004

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 12791229

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