How relevant is the ratio of dietary n-6 to n-3 polyunsaturated fatty acids to cardiovascular disease risk Evidence from the OPTILIP study

There has been much debate over the practical utility of the dietary ratio of n-6 to n-3 polyunsaturated fatty acids in optimizing the benefits of n-3 fatty acids (C18 to C22) on cardiovascular health. This review examines the supporting evidence from the OPTILIP study within the context of the emerging consensus on the value of this dietary metric. The question of whether the ratio of n-6/n-3 polyunsaturated fatty acids or total amounts of dietary polyunsaturated fatty acids is of more importance to cardiovascular health has been addressed recently in a randomly controlled trial (OPTILIP) and in a stable isotope tracer study. These two studies were independently unanimous in concluding that the ratio of n-6/n-3 polyunsaturated fatty acids is of no value in modifying cardiovascular disease risk. The latter study also showed that the absolute amounts of dietary linoleic acid and a-linolenic acid are of relevance to the efficiency of conversion of alpha-linolenic acid to eicosapentaenoic acid and docosahexaenoic acid. This review should help to settle any outstanding controversy over the dietary ratio of n-6/n-3 polyunsaturated fatty acids. It reinforces current recommendations to increase the consumption of preformed eicosapentaenoic acid/docosahexaenoic acid in fish, and supports dietary measures to increase and decrease intakes alpha-linolenic acid and linoleic acid, respectively, to promote the endogenous synthesis of these longer chain n-3 polyunsaturated fatty acids. (Author's abstract)
This review examines the debate over the role of the n-6 to n-3 fatty acid ratio in effecting the conversion of ALA to long chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) There has been sustained interest in the role of dietary ALA as an endogenous and naturally sustainable source of LC n-3 PUFAs. The authors describe the findings of the OPTILIP study which attempted to determine the optimal ratio of n-6/n-3 PUFAs in the UK diet.  The results did not support a role for the relevance of the n-6/n-3 dietary ratio. There is an increasing amount of data to support that the conversion of ALA to LC n-3 PUFAs could be enhanced by decreasing and increasing the absolute amounts of dietary linoleic acid and ALA, respectively. The authors conclude that further study as to how linoleic acid and ALA influence the conversion of ALA, especially under pathophysiological conditions, is required.(Editor's Comments)