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

Key Findings:

The n-6 to n-3 fatty acid ratio will impact the ability of the body to convert ALA to long chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) due to the competition between the two fatty acid families for the necessary enzymes. The results of the OPTILIP study that aimed to determine the optimal ratio of n-6/n-3 PUFAs in the UK diet are reported. It was not clear as to the significance of the n-6/n-3 dietary ratio on conversion in this study. However, an increasing amount of data does support the need to both decrease the n6/n3 ratio and to increase the absolute amounts of ALA to enhance conversion.

ABSTRACT:

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–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 o fn-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)