Omega 6 fatty acids for the primary prevention of cardiovascular disease.

Systematic review of randomized primary-prevention trials in adults without established cardiovascular disease. Participants were drawn from the general population or higher-risk subgroups, including overweight or obese otherwise healthy adults, older men and postmenopausal women, adults with hypercholesterolemia, and overweight or obese adults.

Across the included randomized trials, omega-6 intake was altered by providing specific foods, spreads, and oils or by giving CLA capsules. Active regimens included high-linoleic acid diets, reduced-linoleic acid rapeseed-based diets, a moderate linolenate diet, sunflower-oil-enriched diets, and cis-9,trans-11 conjugated linoleic acid (c9,t11 CLA) capsules at 4 g/day for 24 weeks, compared with lower omega-6 or control diets.

No cardiovascular event data were available. Increasing omega-6 intake did not show consistent effects on blood pressure or lipid levels, and decreasing omega-6 intake likewise showed no clear benefit across the small trials. Examples of reported 24-week results included modest within-group changes in systolic and diastolic blood pressure and mixed, small changes in total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides, without a consistent direction across studies. Overall, evidence was very limited and at risk of bias, so firm conclusions about cardiovascular benefit or harm cannot be drawn.

Evidence came from only a small number of short trials with 664 participants in total and 24-week follow-up. Interventions were heterogeneous, with different foods, oils, and capsule formulations, and the review found no cardiovascular event outcomes. The evidence base was at risk of bias, and adverse effects were not reported.