[Diet and risk of myocardial infarction. A case-control community-based study]

To evaluate diet as a risk factor for myocardial infarction.

Community based case-control study.

University Hospital, Oporto.

First time consecutive cases of acute myocardial infarction (n = 100) and 198 community controls, older than 39 years and living in Oporto, were compared.

Data were collected by trained interviewers using a structured questionnaire designed to obtain information on socio-demographic, medical and behavioural aspects, emphasising the description of diet and food habits (using a semi-quantitative food frequency questionnaire). Controls were selected by random digit dialing with a participation rate of 70%. Odds ratios and 95% confidence intervals (CI) according to quartiles of nutrient ingestion were calculated using unconditional logistic regression.

Female controls presented significantly higher mean intakes of protein, omega-3 fatty acids, fiber, cholesterol and vitamin C. Male controls had a significantly higher mean daily intake of fiber, vitamin C, vitamin E, and carotenes. After adjusting for age, sex, education, body mass index, ethanol, smoking and total energy intake, there was a protective effect of vitamin C (OR = 0.2, 95% CI: 0.1-0.6, for the 4th quartile), vitamin E (OR = 0.3, 95% CI: 0.1-0.9 for the 4th quartile) and total fiber (OR = 0.3, 95% CI: 0.1-0.9) for the 4th quartile). No significant effect was found for trans-fatty acids, but there was a higher risk with increased energy intake.

This study showed that diet has an important independent effect on myocardial infarction, a protective independent role for anti-oxidant vitamin C and E was verified.