Adipose tissue fatty acids and risk of myocardial infarction - a case-control study

Objectives: To study the association between content in adipose tissue of very long-chain n-3 fatty acids, tr-ans fatty acids, linoleic acid and alpha-linolenic acid and risk of a first myocardial infarction. Design and subjects: A case-control design among 100 patients and 98 population controls both men and postmenopausal women, age 45-75 y. Adipose tissue fatty acids were determined by gas-liquid chromatography. Intake data were obtained through interview using a validated food frequency questionnaire. Results: Dietary intake and adipose tissue content of the fatty acids studied correlated significantly. Adipose tissue contents of eicosapentaenoic acid (20:5n-3), docosapentaenoic acid (22:5n-3) and docosahexaenoic acid (22:6n-3) were significantly lower while those of trans fatty acids, linoleic and alpha-linolenic acid were significantly higher in patients than in controls. Age and sex adjusted odds ratios (OR) were significantly reduced with increasing quintiles of very long-chain n-3 fatty acids, thus the OR in the fifth compared to the first quintile was 0.23 (95% CI 0.08-0.70). After further adjustment for waist-to-hip ratio, smoking, family history of CHD and content of trans fatty acids, the OR in the highest quintile was 0.17 (95% CI 0.04-0.76) and the P for trend 0.016. Age and sex adjusted OR was increased in the fifth compared to the first quintile of trans fatty acids (OR 2.81, 95% CI 1.16-6.84), linoleic acid (OR 2.10, 95% CI 0.87-5.07) and alpha-linolenic acid (OR 1.96, 95% CI 0.83-4.61), and P for trend was 0.002. 0.005 and 0.020, respectively. The trends remained significant after adjustment for waist-to-hip ratio, smoking, and family history of coronary heart disease. Trans fatty acids, linoleic acid and alpha-linolenic acid in adipose tissue were strongly correlated, indicating a common source, most likely margarine. When each of these fatty acid species were adjusted for the two others the trends were no longer significant. Conclusion: Intake of very long-chain n-3 Fatty acids as reflected in adipose tissue content is inversely associated with risk of myocardial infarction. Trans fatty acids, linoleic and alpha-linolenic acid were intercorrelated and associated with increased risk. It is suggested that the increased risk may be connected to trans fatty acids or to some other factor associated with margarine consumption.