The role of dietary n-6 fatty acids in the prevention of cardiovascular disease.
n-6 Fatty acids, like n-3 fatty acids, play essential roles in many biological functions. Because n-6 fatty acids are the precursors of proinflammatory eicosanoids, higher intakes have been suggested to be detrimental, and the ratio of n-6 to n-3 fatty acids has been suggested by some to be particularly important. However, this hypothesis is based on minimal evidence, and in humans higher intakes of n-6 fatty acids have not been associated with elevated levels of inflammatory markers. n-6 Fatty acids have long been known to reduce serum total and low-density lipoprotein cholesterol, and increases in polyunsaturated fat intake, mostly as n-6 fatty acids, were a cornerstone of dietary advice during the 1960s and 1970s. In the United States, for example, intake of n-6 fatty acids doubled and coronary heart disease (CHD) mortality fell by 50% over a period of several decades. In a series of relatively small, older randomized trials, in which intakes of polyunsaturated fat were increased (even up to 20% of calories), rates of CHD were generally reduced. In a more recent detailed examination of fatty acid intake within the Nurses' Health Study, greater intake of linoleic acid, up to about 8% of energy, has been strongly related to lower incidence of myocardial infarction or CHD death. Because n-3 fatty acids were also related inversely to risk of CHD, the ratio was unrelated to risk. n-6 Fatty acids reduce insulin resistance, probably by acting as a ligand for peroxisome proliferator-activated receptors-gamma, and intakes have been inversely related to risk of type 2 diabetes. Adequate intakes of both n-6 and n-3 fatty acids are essential for good health and low rates of cardiovascular disease and type 2 diabetes, but the ratio of these fatty acids is not useful. Reductions of linoleic acid to "improve" this ratio would likely increase rates of cardiovascular disease and diabetes.
Willett
Walter C
WC
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts 02115, USA. walter.willett@channing.harvard.edu
D002318:Cardiovascular Diseases / Q000097:blood / Q000517:prevention & control*; D003924:Diabetes Mellitus, Type 2 / Q000517:prevention & control; D043371:Fatty Acids, Omega-6 / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D007333:Insulin Resistance; D019787:Linoleic Acid / Q000494:pharmacology; D008055:Lipids / Q000097:blood; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000187:drug effects / Q000378:metabolism
D043371:Fatty Acids, Omega-6; D008055:Lipids; D016328:NF-kappa B; D018124:Receptors, Tumor Necrosis Factor; D019787:Linoleic Acid