Fattys Acid and the Risk of MI

In the past several decades the reduction of fat intake has been the primary focus of national dietary recommendations to lower risk of coronary heart disease (CHD). A large body of evidence has since shown an individual’s quality of fat intake predicts serum cholesterol levels instead of total fat intake. The focus of CHD prevention currently focuses on replacing saturated fat intake with unsaturated fats. One specific unsaturated fat, namely n-3 (omega) fatty acids, has been recently examined in prospective cohort studies and secondary prevention trials. The results provide strong evidence indicating high intake of omega-3 fatty acids lower ones risk of CHD.
Hu, Manson, and Willet review the effects of saturated fats and trans fats on plasma lipid and lipoprotein levels. Specifically, saturated fatty acids with 12-16 carbon atoms tend to increase plasma total and LDL cholesterol levels, whereas stearic acid (18:0) does not have a cholesterol-raising effect in comparison with oleic acid (18:1). Alternatively, stearic acid may lower HDL compared to unsaturated fatty acids. Myristic acid (14:0) appears to be stronger at raising cholesterol levels compared to lauric acid (12:0) or palmitic acid (16:0), but the data are not entirely consistent. Moreover, trans fatty acids 1) raise LDL cholesterol, 2) increase lipoprotein (a) levels, 3) raise triglyceride levels, 4) negatively affect essential fatty acid metabolism, and 5) promote insulin resistance.
The higher quality fatty acids include mono- and poly-unsaturated fatty acids. Dietary intervention trials using high-polyunsaturated fat diets have been more effective at lowering total serum cholesterol and rates of CHD compared to a low-fat high-carbohydrate diet. Further evidence indicates substituting polyunsaturated fat for trans fat will decrease the risk of CHD. Furthermore, ecological studies have suggested an inverse relationship between monounsaturated fat intake and CHD death. Metabolic studies replacing carbohydrates with monounsaturated fat raises HDL without affecting LDL. In addition, monounsaturated fat is resistant to oxidative modification.
CAD is one important risk factor for the development of an acute myocardial infarction. The February JADA continuing education article adds to the current research of fatty acid intake and acute myocardial infarction (MI). Lopes, Aro, Azevedo, Ramos, and Barros conducted a case-control study which evaluated the relationship between specific fatty acid intake, adipose tissue composition of fatty acids, and acute myocardial infarction in Portuguese men (n=297). Fatty acid intake was assessed using a food frequency questionnaire. The results indicated that the risk of acute MI was significantly reduced by higher intakes of lauric, palmitic, and oleic acids. The association of polyunsaturated fatty acids with the risk of acute MI was non-significant after adjustment for energy intake and cofounders. The adipose tissue results showed an inverse association between acute MI and lauric and oleic acids.

JADA Continuing Education Research Article:

Lopes, C., Aro, A., Azevedo, A., Ramos, E., & Barros, H. Intake and adipose tissue composition of fatty acids and risk of myocardial infarction in a male Portuguese community sample. J Am Diet Assoc. 2007;107:276-286.

Additional Article:

Hu, F. B., Manson, J. E., & Willet, W. C. Types of dietary fat and risk of coronary heart disease: a critical review. Journal of the American College of Nutrition. 2001;20(1):5-19.

Both articles and the JADA Continuing Education Questionnaire can be found at www.eatright.org.