BACKGROUND:There is some dispute about the role of fish and n-3 polyunsaturated fatty acids (n-3 PUFA) consumption on the prevention of coronary heart disease. The aim of this study was to analyze the relationship between n-3 PUFA and fish consumption and the risk of a first acute myocardial infarction (AMI) in a low risk population from Navarre (Spain). METHOD:A hospital-based case-control study was conducted in Pamplona (Spain). We included 171 patients (81% males, age < 80 years) who were admitted with a first acute myocardial infarction and 171 age, gender and hospital-matched controls were selected. A validated semi-quantitative food frequency questionnaire was administered and face-to-face interviews were performed. Conditional logistic regression modeling was used to take into account potential confounders. RESULTS:Adjusted odds ratio (OR) and 95% confidence intervals (CI) for the second and third tertile of n-3 PUFA intake were 0.44 (95% CI, 0.21-0.91) and 0.47 (95% CI, 0.22-1.00), respectively. Trend test was not statistically significant. Adjusted OR and 95% CI for the second and third tertile of fish consumption were 0.40 (95% CI, 0.19-0.83) and 0.42 (95% CI, 0.19-0.93), respectively. Additional adjusting for n-3 PUFA led to a non-significant association between fish consumption and AMI. CONCLUSIONS:This study reveals a protective effect of n-3 PUFA and fish consumption against AMI. Our results suggest that a threshold exists in the quantitative dose-response relationship between fish intake and AMI.