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Background/Objectives. The modern Western diet (MWD) provides high linoleic acid (LA) exposure, typically contributing 6–9% of the total caloric intake. These high LA levels have fueled a longstanding debate about whether this dietary pattern confers benefit or risk. Importantly, LA intake is disproportionately elevated among lower socioeconomic populations due to greater reliance on industrial seed oils and ultra-processed foods. Despite decades of research, controlled dietary intervention studies directly evaluating the biological consequences of varying LA exposure remain limited. Methods. The current randomized, double-blind intervention (ClinicalTrials.gov; NCT02962128; 11 November 2016) compared the effects of a 12-week Low-LA diet (2.5% energy) versus a High-LA diet (10.0% energy) in healthy adults. Outcomes included plasma concentrations of highly unsaturated fatty acids (HUFAs) and ex vivo zymosan-stimulated whole-blood oxylipin generation. Results. Fifty-two participants completed the intervention. High LA exposure resulted in marked reductions in plasma n-3 eicosapentaenoic acid (EPA) and eicosatetraenoic acid (ETA) concentrations compared with the Low-LA arm. Docosapentaenoic acid (DPA) was also significantly lower in weeks 4 and 8. In contrast, levels of the n-6 HUFA arachidonic acid (ARA) did not differ with dietary LA exposure. Conclusions. HUFA and oxylipin analyses revealed that higher dietary LA markedly increased the ratios of ARA to EPA and ARA- to EPA-derived oxylipin species, shifting the lipid mediator balance toward a more n-6-dominant inflammatory profile.
Sergeant et al. (Thu,) studied this question.