1. Introduction
Purpose: The effects of intake of STGs containing esterified eicosapentaenoic acid (EPA) and medium-chain triglycerides (MCTs) on cardiorespiratory endurance have not yet been reported. This study aimed to examine the efficacy of interesterified structured lipids EPA and MCTs on cardiorespiratory endurance. Methods: This 8-week randomized double-blind placebo-controlled parallel-group study involved 19 healthy men. The participants were randomly assigned to a group that received interesterified structured lipids EPA and MCTs (STG group, 9 participants) or a group receiving a PM of EPA and MCTs (PM group, 10 participants). The outcome measures were time to exhaustion (TTE) and time to reach the anaerobic threshold in the peak oxygen uptake (VOOmega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are widely known to be effective in improving cardiovascular function, lowering blood pressure, and improving cognitive function [The effects of the intake of medium-chain triglycerides (MCTs) on endurance have also been investigated. MCTs are tri-esters consisting of three medium-chain fatty acids and a glycerol molecule. MCTs are known to be more easily hydrolyzed and much more rapidly used for energy compared with long-chain triglycerides (LCTs) [Effects on endurance are often examined using endurance tests, multi-stage incremental exercise tests, and the time to reach the anaerobic threshold (AT). A meta-analysis reported that carbohydrate supplementation before or during exercise increased carbohydrate storage in the body during exercise, thereby enhancing endurance performance [Thus, in this study, we hypothesized that the intake of STGs would improve the efficiency of lipid utilization during exercise, which would be accompanied by increases in TTE and peak oxygen uptake (VO