A PROSPECTIVE-STUDY OF PLASMA FISH-OIL LEVELS AND INCIDENCE OF MYOCARDIAL-INFARCTION IN US MALE PHYSICIANS

Objectives. This study evaluated whether increased intake of fish oils (eicosapentaenoic and docosahexaenoic acids) might reduce the risk of coronary heart disease. Background. Observational and clinical studie s have suggested that increased intake of fish oils, as reflected in p lasma levels of fish oils, may reduce the risk of myocardial infarctio n. Methods. A nested case-control study was conducted among the 14,916 participants in the Physicians' Health Study with a sample of plasma before randomization. Each participant with myocardial infarction occu rring during the first 5 gears of follow-up was matched by smoking sta tus and age with a randomly chosen control participant who had not dev eloped coronary heart disease. Results. Mean levels of fish oils (with 95% confidence interval [CI] for paired differences and p values) in case and control participants, expressed as percent of total fatty aci ds, were, for eicosapentaenoic acid, 0.26 versus 0.25 (95% CI -0.03 to 0.05, p = 0.70) in cholesterol esters and 0.56 versus 0.54 (95% CI -0 .04 to 0.09, p = 0.44) in phospholipids, and for docosahexaenoic acid, 0.23 versus 0.24 (95% CI -0.07 to 0.04, p = 0.64) in cholesterol este rs and 2.22 versus 2.14 (95% CI -0.10 to 0.27, p = 0.36) in phospholip ids. Results adjusted for major cardiovascular risk factors showed a v ery similar lack of association between fish oil levels and the incide nce of myocardial infarction. Conclusions. These results indicate no b eneficial effect of increased fish oil consumption on the incidence of a first myocardial infarction. However, the effect of very high level s of fish oils could not be evaluated.