Increasing dietary linoleic acid does not increase tissue arachidonic acid content in adults consuming Western-type diets: a systematic review

Abstract

BackgroundLinoleic acid, with a DRI of 12-17 g/d, is the most highly consumed polyunsaturated fatty acid in the Western diet and is found in virtually all commonly consumed foods. The concern with dietary linoleic acid, being the metabolic precursor of arachidonic acid, is its consumption may enrich tissues with arachidonic acid and contribute to chronic and overproduction of bioactive eicosanoids. However, no systematic review of human trials regarding linoleic acid consumption and subsequent changes in tissue levels of arachidonic acid has been undertaken.ObjectiveIn this study, we reviewed the human literature that reported changes in dietary linoleic acid and its subsequent impact on changing tissue arachidonic acid in erythrocytes and plasma/serum phospholipids.DesignWe identified, reviewed, and evaluated all peer-reviewed published literature presenting data outlining changes in dietary linoleic acid in adult human clinical trials that reported changes in phospholipid fatty acid composition (specifically arachidonic acid) in plasma/serum and erythrocytes within the parameters of our inclusion/exclusion criteria.ResultsDecreasing dietary linoleic acid by up to 90% was not significantly correlated with changes in arachidonic acid levels in the phospholipid pool of plasma/serum (p = 0.39). Similarly, when dietary linoleic acid levels were increased up to six fold, no significant correlations with arachidonic acid levels were observed (p = 0.72). However, there was a positive relationship between dietary gamma-linolenic acid and dietary arachidonic acid on changes in arachidonic levels in plasma/serum phospholipids.ConclusionsOur results do not support the concept that modifying current intakes of dietary linoleic acid has an effect on changing levels of arachidonic acid in plasma/serum or erythrocytes in adults consuming Western-type diets.

Plasma fatty acids, oxylipins, and risk of myocardial infarction: the Singapore Chinese Health Study

“…However, our data suggest that plasma LA is not associated with AMI risk, and LA is not necessarily associated with higher AA concentrations (r = 0.06). In line with this finding, wide variation of dietary LA intake did not substantially affect tissue AA concentrations in a meta-analysis of feeding trials (31). Therefore, it is unlikely that dietary LA increases risk of AMI through conversion to AA.…”

Botanical oils enriched in n-6 and n-3 FADS2 products are equally effective in preventing atherosclerosis and fatty liver

“…Many n-6 PUFA-enriched botanical oils contain LA as the predominant fatty acyl species, accounting for 85-90% of n-6 PUFA consumption in the US ( 10 ). However, as discussed above, diets enriched in LA do not result in plasma and tissue AA enrichment ( 44,63 ). Genetic deletion of Elovl5, the gene encoding the enzyme that elongates 18:3 n-6 to 20:3 n-6 and 18:4 n-3 to 20:4 n-3, results in diminished hepatic lipid AA and DHA and increased neutral lipid storage ( 64 ).…”

“…Concerns that elevated membrane AA may result in increased cellular infl ammation that exacerbates atherosclerosis lack support in human studies ( 13 ). Moreover, LAenriched diets have not enriched AA in plasma and tissue lipid fractions ( 40,43,44 ), likely due to ineffi cient FADS2 conversion of LA to AA ( 45,46 ). In addition, a recent meta-analysis of 13 cohort studies (involving 310,602 individuals and 12,479 coronary heart disease events) revealed an inverse association between dietary LA intake and coronary heart disease risk, such that a 5% increase in energy intake from LA was associated with a 10% and 13% lower risk of coronary heart disease events and deaths, respectively ( 12 ).…”

Omega-6 Fatty Acids and Cardiovascular Disease

“…The authors concluded, "Our results do not support the concept that modifying current intakes of dietary linoleic acid has an effect on changing levels of arachidonic acid in plasma, serum or erythrocytes in adults consuming Westerntype diets." 9 The opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.…”