Background: Intake of long-chain n-3 fatty acids found in fish is low in many countries worldwide. alpha-Linolenic acid could be a viable cardioprotective alternative to these fatty acids in these countries.
Methods and results: Cases (n=1819) with a first nonfatal acute myocardial infarction and population-based controls (n=1819) living in Costa Rica matched for age, sex, and area of residence were studied. Fatty acids were assessed by gas chromatography in adipose tissue samples and by a validated food frequency questionnaire specifically designed for this population. Odds ratios and 95% confidence intervals were calculated from multivariate conditional logistic regression models. alpha-Linolenic acid in adipose tissue ranged from 0.36% in the lowest decile to 1.04% in the highest decile. The corresponding median levels of intake were 0.42% and 0.86% energy. Greater alpha-linolenic acid (assessed either in adipose or by questionnaire) was associated with lower risk of myocardial infarction. The odds ratios for nonfatal myocardial infarction for the highest compared with the lowest deciles were 0.41 (95% confidence interval, 0.25 to 0.67) for alpha-linolenic acid in adipose tissue and 0.61 (95% confidence interval, 0.42 to 0.88) for dietary alpha-linolenic acid. The relationship between alpha-linolenic acid and myocardial infarction was nonlinear; risk did not decrease with intakes > approximately 0.65% energy (1.79 g/d). Fish or eicosapentaenoic acid and docosahexaenoic acid intake at the levels found in this population did not modify the observed association.
Conclusions: Consumption of vegetable oils rich in alpha-linolenic acid could confer important cardiovascular protection. The apparent protective effect of alpha-linolenic acid is most evident among subjects with low intakes.