Effects of eight weeks of eicosapentaenoic acid and medium-chain triacylglycerol structured lipid intake on EPA/AA ratio and muscle performance in young men

BACKGROUND: Structured triglycerides (STGs), in which eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are esterified with medium-chain triglycerides (MCTs), have demonstrated greater bioavailability and potential benefits in improving endurance and reducing post-exercise strength loss compared with physical mixtures (PMs) of EPA and MCTs. However, it remains unclear whether STGs have superior effects on blood EPA levels and muscular endurance and fatigue. This study compared the effects of 8-week STG and PM intake on blood EPA levels, muscular endurance, and fatigue following resistance exercise. METHODS: Twenty-eight healthy young men were randomly assigned to an STG group (n = 15) or a PM group (n = 13) in a double-blind, parallel-group, active comparator trial. Participants consumed 4,560 mg/day of the test oil (600 mg EPA, 260 mg DHA) for 8 weeks. After the intervention, the participants performed four sets of leg extensions to exhaustion at 40% of their body weight. Muscular endurance was assessed by the number of repetitions, and fatigue was evaluated by changes in maximal voluntary contraction, range of motion, thigh circumference, muscle thickness, echo intensity, and jump performance. RESULTS: The STG group showed a significantly greater increase in the serum EPA/arachidonic acid (AA) ratio compared with the PM group. However, no significant differences were found between groups in repetition counts or fatigue-related measures. CONCLUSION: Eight weeks of STG supplementation improved the blood EPA/AA ratio more than a PM, but did not yield superior effects on muscle endurance or fatigue.