Science Advisory from the American Heart Foundation on Omega-6 Fatty Acids
Harris WS et al., Circulation. 119 :1-6. 2009.
American Heart Association Science Advisory and Coordinating Committee
Since many individuals and commercial groups have advised considerable reductions in the intake of omega-6 (n-6) polyunsaturated fatty acids (PUFA) for improving health, the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism along with the Council on Cardiovascular Nursing and Council on Epidemiology and Prevention have reviewed evidence on the relationship between the intake of omega-6 PUFA and the risk of coronary heart disease (CHD) and cardiovascular disease (CVD). The advisory committee pointed out in this recent publication that the vast majority of omega-6 PUFA as consumed in the US diet is present as linoleic acid (LA) representing approximately 6.7% of total energy intake (approximately 14.8 grams/day) with a very minor portion coming in the form of arachidonic acid (AA) at approximately 0.15 g/day. LA is consumed from LA-rich plant oils (corn oil, safflower oil, soybean oil, others) and animal food products while AA is consumed primarily via animal-based foods (meat, eggs, and some fish). The committee points out that AA (not LA) is the immediate substrate for the biosynthesis of a variety of pro-inflammatory compounds (eg., in white blood cells, elsewhere) and that cellular AA can be derived from the direct consumption in the diet of AA or via the consumption of LA which can be metabolically converted by desaturation-elongation reactions in the body to form AA.
After extensive evaluation of the combined data from numerous randomized trials, case-control and cohort studies, and long-term animal feeding experiments, the present advisory indicated that the consumption of 5-10% of energy from omega-6 PUFA (mainly as LA) appears to significantly reduce the risk of CHD relative to lower intakes. In conclusion, the Committee reports that the American Heart Association ‘supports an omega-6 PUFA intake of at least 5-10% of energy in the context of other AHA lifestyle and dietary recommendations’. They also conclude that reducing omega-6 PUFA intakes from their current levels would be more likely to increase than to decrease the risk for CHD.
This advisory from the American Heart Association is of considerable importance since various individuals and groups have widely promoted the concept that the current relatively high intakes of omega-6 PUFA in the North American diet are likely deleterious for CVD and associated events and that the relatively high omega-6:omega-3 ratio in the diet may also be a contributing factor to premature CVD and associated mortality. It should be noted that the vast majority of the dietary omega-6 and omega-3 are represented by LA and LNA (alpha-linolenic acid), respectively. In contrast, the blood omega-6 is very rich in LA plus AA with the omega-3 represented mainly by EPA plus DHA plus DPA (docosapentaenoic acid).