Bottomline: The typical American diet, high in omega-6 fat increases the risk for atherosclerosis for those with a genetic susceptibility, according to Tufts University scientists.

Summary: Researchers from Tufts University found that people who have a variation of a gene (apolipoprotein A5 or APOA5) have a higher risk for heart disease, especially if they eat a diet rich in omega-6 polyunsaturated fats.   The scientists found that omega-6 fats have a specific interaction with this gene, which increases the formation of a more dangerous type of LDL cholesterol, and raises triglycerides (fat) in the blood.  Elevation of either of these compounds increases the risk for heart disease.  Notably, this aberrant gene has been identified in many ethnic groups, especially Hispanic and Asian ethnicities.   Circluation (2006):113: 2062

Study Conclusion: “...omega-6 polyunsaturated fat–rich diets are related to a more atherogenic lipid profile in these subjects.”

Comment: Most dietary intervention studies using polyunsaturated fat-rich diets have been performed in non-Hispanic whites. This could be one reason why the deleterious effects of high polyunsaturated fat diets (aka high omega-6 diets) is missed. Notably, the level of omega-6 fat eaten by the people in this study is typical of the American diet. This is the second key study finding that high omega-6 fats increases risk for heart disease for genetically susceptible people, but on an entirely different gene. N Engl J Med 2004 350: 29-37

Link to Free Full Text:

Chao-Qiang Lai et al. Dietary Intake of n-6 Fatty Acids Modulates Effect of Apolipoprotein A5 Gene on Plasma Fasting Triglycerides, Remnant Lipoprotein Concentrations, and Lipoprotein Particle Size: The Framingham Heart Study.Circulation (2006) 113: 2062-2070.

Dwyer, J et al Arachidonate 5-Lipoxygenase Promoter Genotype, Dietary Arachidonic Acid, and Atherosclerosis N Engl J Med 2004 350: 29-37.