Observational studies have examined the relationship between fish consumption and coronary heart disease (CHD) risk, but none has had adequate statistical power to support a conclusion. Whelton and associates pooled the data available from multiple observational studies about the consumption of fish and fish oils.
A total of 19 cohort and case-control studies were included in the analysis. All studies were conducted in adult humans, used an observational case-control or cohort study design, compared a group who regularly consumed fish with a group who consumed little or no fish, included CHD as an outcome, and reported the association of fish consumption categories with CHD as a relative risk, hazard ratio, or odds ratio. Fish consumption was recorded in different ways in the studies, and a dietitian converted the quantity of fish consumed to the number of servings consumed weekly.
The pooled relative risk of fatal CHD in persons consuming any amount of fish versus those who consumed little or no fish was 0.83 (95 percent confidence interval, 0.76 to 0.90; P < .005). An inverse relationship was noted between fish consumption and fatal CHD in all but one subgroup. This inverse relationship was more striking in persons consuming two or more servings of fish per week compared with those who ate fewer than two servings per week. The protective effect of fish consumption was slightly greater in women than in men.
The authors conclude that fish consumption is associated with a significantly lower rate of fatal and total CHD. Recommendations of increased fish consumption may be useful in both primary and secondary CHD prevention.
editor’s note: The protective effect of n-3 polyunsaturated fatty acids in patients with CHD has been documented.1 The amount of omega-3 fish oil supplements used in most studies was the equivalent of eating two or more servings of fish per week. Based on this meta-analysis, daily consumption of fatty fish such as herring, mackerel, or salmon, or approximately 12 g of a fish-oil supplement may be recommended to lower the adverse event risk in patients with CHD. Fish oils also have been suggested to reduce fatal arrhythmias after acute myocardial infarction.2 Other probable benefits include decreased platelet aggregation, improved lipid profiles, enhanced endothelial function, and decreased inflammation. Two cautions should be considered. First, high doses of fish oils in persons with type 2 diabetes who have hypertriglyceridemia may lower triglyceride levels but also raise levels of low-density lipoprotein cholesterol.3 Further study on how this affects vascular events is needed. Second, fish oils may raise the International Normalized Ratio in patients taking warfarin.4—r.s.