Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study).

BACKGROUND: The omega-3 (n-3) index (O3I), reflecting the percentage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocyte membranes, is associated with reduced risk of cardiovascular disease (CVD). United Kingdom dietary guidelines recommend 2 portions of fish/week (280 g/wk) or supplementation of ∼500 mg EPA + DHA/d for non/low-fish consumers; however, the impact of these recommendations on the O3I is unclear. OBJECTIVES: The aim of this study was to explore the influence of the current guidance for fish consumption and ω-3 supplementation on the O3I among young adults. METHODS: Healthy adults aged 18-30 y (n = 40) with low-fish intake and O3I <6% were randomly assigned to receive either 2 fish (1 portion oily fish and 1 portion white fish) or 2 nonfish meals per week as well as a daily 700 mg EPA+DHA supplement capsule or placebo capsule for 8-wk in a 2×2 factorial design. The effects on lipid profiles and high-sensitivity C-reactive protein (hs-CRP) were also examined. RESULTS: Consumption of 2 portions of fish/week and ω-3 supplementation resulted in a significant mean % increase in O3I of 2.27% ± 0.82% and 2.03% ± 0.88%, respectively. Both interventions also significantly increased total erythrocyte n-3 polyunsaturated fatty acids (n-3 PUFAs) (+3.11% ± 1.79% and +2.00% ± 1.24%) and lowered total n-6 PUFAs (-1.94% ± 1.65% and -2.60% ± 1.16%) (all false discovery rate P < 0.05). There were no significant effects on blood lipids or hs-CRP. CONCLUSIONS: In support of current dietary guidelines for fish consumption and ω-3 intake, 2 portions of fish/week or ω-3 supplementation are effective strategies for increasing the O3I. These findings support the efficacy of current public health recommendations for fish consumption and ω-3 intake as early dietary interventions to reduce CVD risk through increasing the O3I among young adults. This trial was registered at www. CLINICALTRIALS: gov as NCT06729229.