This study aimed to investigate the effect of supplementation of fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on the damage of the biceps brachii after eccentric contractions (ECCs) of the elbow flexors, particularly focusing on muscle stiffness. Sixteen men were included in this double-blind, placebo-controlled, parallel design study and the participants were randomly assigned to the EPA and DHA supplement group (EPA, n = 8) and placebo group (PL, n = 8). They consumed either EPA 600 mg and DHA 260 mg per day or placebo supplement for 8 weeks prior to exercise. Moreover, they performed six sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using a dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, muscle echo intensity, and muscle stiffness were assessed before exercise; immediately after exercise; and 1, 2, and 5 days after exercise. MVC torque and ROM were significantly higher in the EPA group than in the PL group after ECCs (p < 0.05). Muscle soreness, upper arm circumference, and muscle echo intensity were significantly higher in the PL group than in the EPA group after ECCs (p < 0.05). In addition, muscle stiffness at 150° was significantly higher in the PL group than in the EPA group immediately after ECCs (p < 0.05). The present study showed that EPA and DHA supplementation has a positive role in inhibiting muscle stiffness after ECCs. This trial (UMIN000028165) was registered on 10th/July/2017.

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)—omega-3 fatty acids with various functions—influence sleep in children and young adults. However, only limited studies on their effects on sleep in middle- and old-aged adults have been reported. Therefore, we investigated the effects of DHA and EPA on sleep quality in subjects aged ≥ 45 years. We performed a randomized, placebo-controlled, double-blinded, parallel-grouped study, in which we randomly assigned 66 healthy Japanese males and females. Each individual received six 480 mg capsules containing 576 mg DHA and 284 mg EPA per day (DHA/EPA group, n = 33), or corn oil (placebo group, n = 33), for 12 weeks. Before and after the intervention, the Oguri-Shirakawa-Azumi sleep inventory MA version (OSA-MA) and the sleep state test were conducted. In the DHA/EPA group, factor III (frequent dreaming) scores among the OSA-MA scores were significantly improved compared to the placebo group. Additionally, sleep state tests revealed that sleep efficiency improved in the DHA/EPA group. To our knowledge, this study is the first to report that DHA/EPA improves sleep quality in middle- and old-aged individuals, even at doses lower than those administered in previous studies.

Background: Although the ingestion of total omega–3 fatty acids (omega–3) is positively related with muscular strength in older persons, little is known about the effect of omega–3 plasma levels on muscular function before and after exercise in young men. Moreover, omega–3 supplementation has a positive role in exercise-induced acute muscle damage. This study investigated the relationship between plasma omega–3 in the blood and promotion and preservation of muscle strength after eccentric contractions (ECCs) in young men. Methods: Thirty-two healthy young men participated in this study. We assessed plasma omega–3 level and the maximal voluntary contraction (MVC). Twenty-six out of them exercised 60 ECCs at 100% MVC. We measured the MVC torque, flexibility before and immediately after exercise, 1–5 days post exercise. Results: The levels of eicosapentaenoic acid (EPA) and EPA/arachidonic acid were positively associated with muscle strength (p < 0.05). Higher levels of omega–3 EPA and docosahexaenoic acid prevented the reduction in the MVC and limited joint flexibility after ECCs. Conclusions: The present study reveals that higher levels of EPA are important to promote muscle strength and preserve the strength loss after exercise.

Dihomo-γ-linolenic acid (DGLA) is an n-6 polyunsaturated fatty acid that has been shown to have anti-inflammatory and anti-allergic effects in mice and cell study. To date, however, no human intervention study has examined the effects of DGLA. Therefore, we investigated the effects of DGLA on pollen-induced allergic symptoms in healthy adults. We performed a randomized, double-blind, placebo-controlled, parallel-group study comprising healthy Japanese men and women. Each subject received four 250 mg capsules providing 314 mg DGLA/day (DGLA group, n = 18) or olive oil (placebo group, n = 15) for 15 weeks. The primary outcomes, classification of the severity of allergic rhinitis symptoms (CSARS), and the Japanese Rhino-conjunctivitis Quality of Life Questionnaire (JRQLQ) served as symptom scores during the pollen season. In the DGLA group, the cedar pollen associated symptoms of sneezing and a blocked nose in the CSARS were significantly lower than those in the placebo group (p < 0.05, p < 0.01, respectively). Significant trends were observed the symptoms of runny nose in the CSARS and total symptom score (TSS) in the JRQLQ for cedar pollen (p < 0.1). To our knowledge, this is the first study to report the effects of DGLA in humans, and the results suggest that DGLA is effective in reducing allergic symptoms caused by pollen.

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 (VO₂peak) test, VO₂peak, and anaerobic threshold. Results: The increase in TTE in the VO₂peak test after the intervention period compared with before the intervention period was significantly greater in the STG group (53 ± 53 s) than in the PM group (−10 ± 63 s; p < 0.05). Similarly, the increase in time to reach the anaerobic threshold was significantly greater in the STG group (82 ± 55 s) than in the PM group (−26 ± 52 s; p < 0.001). Conclusion: This study demonstrated that the consumption of interesterified structured lipids EPA and MCTs improved endurance in humans.

Background: Structured lipids, composed of re-esterified triacylglycerols containing eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and medium-chain fatty acids, may influence metabolism and endurance performance. This trial aimed to evaluate the effects of eight weeks of structured lipid supplementation on substrate utilization, erythrocyte fatty acid content, and endurance performance in healthy untrained men. Methods: In a double-blind, placebo-controlled, randomized design, 36 participants (18 per group) received either structured lipids or placebo supplementation for eight weeks. Pre- and post-supplementation assessments included maximal oxygen uptake, time to exhaustion, substrate oxidation during exercise at 65% VO_2max, and erythrocyte membrane fatty acid content. Non-parametric statistical methods were used to analyze within- and between-group differences. Results: After supplementation, the structured lipids group showed statistically significant within-group changes in substrate utilization, including lower respiratory exchange ratio and higher percentage fat oxidation, total fat oxidation, and mean fat oxidation rate. Statistically significant increases were also observed in erythrocyte EPA + DHA content and time to exhaustion. Compared with the placebo group, the structured lipids group showed statistically significant post-intervention differences in substrate oxidation, erythrocyte EPA + DHA levels, and time to exhaustion. Conclusions: Eight weeks of structured lipid supplementation increased erythrocyte membrane EPA and DHA and enhanced fat oxidation during moderate-intensity exercise in untrained men. Although endurance performance improved, the change was within natural variability and showed substantial interindividual differences. Further rigorously controlled studies are needed to determine whether these metabolic adaptations yield meaningful functional benefits.