|Nutrition Evidence Library|
Bucher HC, Hengstler P, Schindler C, Meier G. N-3 polyunsaturated fatty acids in coronary heart disease: A meta-analysis of randomized controlled trials. Am J Med. 2002 Mar; 112(4): 298-304.
PubMed ID: 11893369
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Research Design and Implementation Rating:
POSITIVE: See Research Design and Implementation Criteria Checklist below.
To investigate the effects of dietary and non-dietary (supplemental) intake of n-3 polyunsaturated fatty acids (PUFA) on coronary heart disease.
Studies including patients who underwent coronary bypass surgery or heart transplant surgery.
Description of Study Protocol:
Searched MEDLINE, EMBASE, Pascal BioMed, Cochrane Library and Index Medicus; all languages included.
Search strings included n-3 fatty acids, fish oils, diet, dietary therapy and cardiovascular disease with random or control.
Study eligibility and quality determined by blinded assessment of two pairs of investigators. A scoring system was used that took into account randomization of participants, blinding and description of withdrawals and drop-outs, with one point given for each. An additional point was given if randomization was concealed (central allocation) and double blinding with identical placebo, yielding scores from zero to five.
Data Collection Summary:
Outcomes of interest were fatal and non-fatal MI and mortality data. Plasma lipids were also analyzed when reported by studies.
Publication bias assessed by inspecting funnel plots. Data pooled from each trial using fixed-effects model. Random effects model was used if Breslow-Day test for heterogeneity yielded P<0.10.
Variability (heterogeneity) of study results explored by the magnitude of the treatment effects in relation to intervention type (supplementation vs. diet), duration of intervention and blinding methods used.
Researchers tested the differences in combined estimates of subgroups, and used the z-score for each subgroup by dividing the difference in the log relative risk of the subgroup summary by the standard error of the difference.
Description of Actual Data Sample:
A literature search identified 406 studies and 369 articles reviewed in the Cochrane Library.
177 Trials Were Identified
11 Trials Included
Of the studies used:
Summary of Results:
Incidence of Non-fatal and Fatal MI in Patients Treated with n-3 PUFA-Enhanced Diets vs. Control (N=10)
No a priori hypotheses explained the heterogeneity observed. For all endpoints where authors found statistically significant heterogeneity, summary estimates were similar in all subgroups. See sensitivity analysis results below.
A diet supplemented with n-3 PUFA may decrease mortality due to myocardial reinfarction, sudden death and overall mortality in patients with CAD.
The mortality in control groups of trials that followed patients for an average of 1.5 years varied from 1% t 22%, suggesting that in low-risk patients with mortality of about 2% per year, 250 patients would need to receive n-3 PUFA supplementation for 1.5 years to prevent a single premature death. In patients with higher mortality rates (22%), 24 patients would need to supplement with n-3 PUFA for 1.5 years to prevent one event.
Addressed limitations of this review include:
The anti-lipidemic effect of n-3 PUFA was limited to an average of 20% reduction in TG levels, with little effect on LDL and HDL.
Low number of dietary trials met inclusion criteria. May limit generalizabilty regarding effectiveness of n-3 PUFA containing diets and cardiac outcomes until more strong dietary studies are published.
Researchers did not address variance in quantities contained in the n-3 PUFA supplements on clinical outcomes. Unable to determine effective dose with this analysis.
Results generalizable primarily to borderline and hyperlipidemic individuals. Gender breakdown of including studies not stated further limiting generalizabilty.
Copyright American Dietetic Association (ADA).