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N-3 polyunsaturated fatty acids help reduce coronary death

 

This meta-analysis investigates the effects of dietary and nondietary (i.e. supplemental) intake of n-3 polyunsaturated fatty acids on coronary heart disease.

Bottom line

This paper finds that n-3 polyunsaturated fatty acids reduce the risk of mortality due to myocardial reinfarction, sudden death and overall mortality in patients with coronary heart disease.

Reference

HC Bucher et al. N-3 polyunsaturated fatty acids in coronary heart disease: a meta-analysis of randomized controlled trials. American Journal of Medicine 2002 112: 298-304.

Search

The literature was searched using several databases (e.g. MEDLINE, Embase) for randomised controlled trials, published in all languages from 1966 to 1999. The Cochrane Library and references of identified papers were also examined. To be included, trials had to have compared dietary or supplemental intake of n-3 polyunsaturated fatty acids with a control diet or placebo in patients with coronary heart disease and followed them for at least six months.

Eleven trials met these criteria: two using dietary intervention and nine using supplementation. There were a total of 7,951 patients in the intervention groups (range 31 to 5,666) and 7,855 patients in the control groups (range 28 to 5,658). The mean age was 49 to 66 years; between 33% and 100% had a previous myocardial infarction; and the average follow-up lasted 20 months (range 6 to 46 months).

Results

In patients with coronary heart disease, diets enriched with n-3 polyunsaturated fatty acids:

Comment

The strength of this meta-analysis is that it only included randomised controlled trials, but unfortunately it has the usual limitations, e.g. small sample sizes (there were 300 or fewer participants in nine of the trials) and the amount and type of n-3 polyunsaturated fatty acid varied considerably. It is therefore difficult to infer anything beyond the observed associations, e.g. the size of the risk reductions; the amount of n-3 fatty acids required to achieve them; or the differences (if any) between dietary and supplemental n-3 polyunsaturated fatty acids.

However, the current UK recommendation is to eat one to two portions of oil-rich fish per week. A separate recommendation of a weekly intake of 1.5 g (i.e. one small serving) of eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) has also been made. (The trials in this analysis used supplements of EPA and DHA, with doses varying from 0.3 to 6.0 g and 0.6 to 3.7 g respectively.)

The protective effect of n-3 polyunsaturated fatty acids has been attributed to EPA and DHA, which are present in fish oil and the flesh of oil-rich fish (e.g. mackerel, salmon, kippers, herring), and alpha-linolenic acid, the richest sources of which are seed oils (e.g. rapeseed and soya) and nuts (e.g. walnuts). For those who do not like or do not eat fish, supplements containing n-3 fatty acids are an option, although it is better to obtain them through dietary sources.