OMEGA-3. FATTY ACIDS

• EPA and DHA supplementation can support endurance capacity and cardiovascular function during aerobic exertion. The authors note, however, that the direct effect on endurance results is not unambiguous across all studies.
• Omega-3 supplementation in combination with resistance training can support strength development, and this effect may depend on dose and duration of use. At the same time, the authors indicate that in young adults, supplementation may not bring clear benefits in terms of muscle hypertrophy.
• The position statement also indicated the possibility of reducing subjectively perceived muscle soreness after intensive exertion, which may have significance in the context of post-exercise recovery. The authors note, however, that more objective recovery indicators do not show equally consistent effects.
• The authors also draw attention to the possible beneficial influence of omega-3 supplementation on selected immune cell responses in athletes, although they emphasize that, due to methodological differences between studies, conclusions in this area require caution.
• Omega-3 supplementation may also show neuroprotective potential in athletes exposed to repeated head impacts, but the authors note that data from research in humans remain limited.
• In summarizing the position statement, they noted the link between omega-3 supplementation and improved sleep quality. The authors indicate, however, that this area still requires further research, particularly concerning individual fatty acids and their mechanisms of action.

Key conclusions

• Omega-3 acid supplementation may support the anti-inflammatory response after exertion. In the case of interleukin 6, results indicated improvement after supplementation, while in two studies, C-reactive protein values were significantly higher in the control groups than in the supplemented groups.
• Supplementation may also limit selected muscle damage markers. In 3 of 4 studies analyzing creatine kinase and lactate dehydrogenase, the values of these markers were significantly higher in the control groups than in the omega-3 groups.
• The effect of supplementation on delayed muscle soreness after exertion was not unambiguous. The authors indicate that results regarding muscle soreness were mixed.
• The publication also noted a beneficial influence on selected oxidative stress indicators, including the ratio of reduced to oxidized glutathione. The authors note, however, that the number of available studies remains limited.
• Potential benefits concerned primarily EPA and DHA. The authors emphasize that the only study using ALA showed no benefits in healthy, physically active people.

Key conclusions

• The authors indicate that EPA and DHA supplementation can beneficially affect selected indicators associated with capacity, recovery and limiting the risk of injury or illness, but these changes do not always translate into a clear improvement in final sport results.
• In the area of capacity, some studies suggested a beneficial influence on parameters associated with aerobic exertion, such as heart rate during submaximal exertion, oxygen uptake or the aerobic ceiling. Not all interventions, however, translated into improvements in time to exhaustion, time trials or other direct indicators of sport performance.
• In the area of recovery, the data was more consistent, particularly in relation to muscle soreness after exertion. The authors conclude that EPA and DHA may affect markers associated with the inflammatory response and oxidative stress, and one of the more frequently observed effects was the reduction of delayed muscle soreness.
• The authors note that more beneficial results were more often observed in studies of longer duration. In their exploratory analysis, effects regarding capacity more often appeared in studies lasting over 5 weeks in athletes and over 8 weeks in amateurs, while in the area of recovery they were more often observed after 8 weeks in athletes and 6 weeks in amateurs.
• Dose may also matter, but the authors treat this conclusion as descriptive, resulting from the division of the studies analyzed. In the capacity part, more beneficial results were observed at doses above approximately 2 g per day in athletes and 1.8 g per day in amateurs, and in the recovery part, more beneficial effects more often appeared at doses above approximately 1.14 g per day.
• The authors conclude that more beneficial effects of supplementation were more often observed in amateur-active people than in elite athletes. They note, however, that this may result both from differences in training status and from study design, including the duration of the intervention and the greater difficulty of obtaining measurable improvement in well-trained athletes.
• In the part concerning the risk of injury or illness, data was described suggesting a possible neuroprotective effect of DHA in American football players and a beneficial influence on selected lung function indicators in exercise-induced bronchospasm, although the number of such studies was small.
• In their final conclusions, the authors indicate that beneficial effects of supplementation were more often observed after about 6 to 8 weeks and at doses above approximately 1.5 to 2.0 g per day, but at the same time emphasize the need for better-designed studies that will allow precise determination of the optimal dose and duration of use. 

Key conclusions

• The authors indicate that the most repeatable effects of supplementation concerned reaction time, mood, the cardiovascular response in cyclists, muscle recovery, TNF-α production by immune cells and nitric oxide response after exertion.
• The most consistent results were observed in the area of the central nervous system, cardiovascular system, pro-inflammatory cytokines and skeletal muscle.
• In the area of muscle recovery, results were among the most promising. In 4 of 7 randomized studies, a beneficial influence was noted on indicators such as muscle soreness, creatine kinase activity and selected countermovement jump parameters. At the same time, results concerning training adaptations and direct exercise effects remained inconsistent.
• In the area of aerobic capacity and sport results, unambiguous benefits were not demonstrated. The authors emphasize that supplementation did not noticeably affect endurance capacity, oxygen consumption, muscle strength or training adaptation.
• In studies involving athletes, beneficial changes in cardiovascular response and oxygen consumption were observed, but this concerned mainly laboratory controlled studies conducted in cyclists and did not translate unambiguously into improvement in sport results.
• In some studies, supplementation was associated with reduced TNF-α production by immune cells, while results concerning other inflammatory markers were more varied.
• The authors also note that few adverse effects were reported, but they draw attention to the significance of product quality and the need for better reporting of supplement composition in future studies.

Key conclusions

• The authors cite studies in which 8 weeks of supplementation with 1.86 g EPA and 1.50 g DHA per day enhanced the muscle protein synthesis response to amino acid and insulin intake in young and older adults. At the same time, no effect on muscle protein synthesis in the fasted state was observed.
• In the cited study in healthy older people, 6 months of supplementation with 1.86 g EPA and 1.50 g DHA per day was associated with an increase in fat-free body mass and a clinically significant improvement in selected muscle parameters.
• Particularly interesting results were noted during periods of activity limitation. The authors describe a study in which 6 weeks of supplementation with approximately 3 g EPA and 2 g DHA per day weakened the decline in volume and mass of muscle during 2 weeks of leg immobilization in young women. In the following 2 weeks of free return to activity, participants in the omega-3 group regained the lost muscle volume, which was not observed in the control group.
• The beneficial effect under conditions of immobilization was associated with an increase in daily integrated myofibrillar protein synthesis and the preservation of selected mitochondrial function parameters. The authors note, however, that the study concerned a simple model of muscle inactivity in young women, not a clinical situation with accompanying inflammation after injury or surgery.
• The authors also indicate that incorporation of EPA and DHA into membrane phospholipids may be associated with increased muscle protein synthesis, changes in the expression of factors regulating protein breakdown and improvement in mitochondrial respiration kinetics. At the same time, they emphasize that the precise mechanisms responsible for these effects have not yet been unambiguously explained.
• An important reservation is that not all studies confirm the anabolic action of omega-3. The authors also cite work in which 8 weeks of supplementation did not significantly affect myofibrillar muscle protein synthesis in young men, and another study did not show an effect on the rate of myofibrillar protein synthesis or muscle mass in older adults during resistance training.

Key conclusions:

• Main bioavailability result: taking the average of two natural fish oils (FBO and CLO) as 100%, the relative bioavailability of EPA + DHA was 124% dla rTG, 91% dla FFA ratio, and 124% for rTG, 91% for FFA and 73% for EE.After correcting for actual dose values, it amounted respectively to 134%, 86% and 76%.
• Comparison of EE with other forms: differences in total EPA + DHA were statistically significant when comparing EE with rTG (p = 0.0001) and EE with FBO (p = 0.024). They were not statistically significant when comparing EE with CLO (p = 0.13) and EE with FFA (p = 0.25).
• Comparison of rTG with other forms: the bioavailability of rTG was statistically significantly higher than FFA (p = 0.006) and CLO (p = 0.002), while it did not differ significantly from FBO (p = 0.24).
• Mechanism of differences between forms: the authors indicate that the lower bioavailability of EE is consistent with earlier reports, according to which pancreatic lipase hydrolyzes ethyl esters to a lesser extent and more slowly than triglycerides. They additionally note that EE contains not only triglycerides (approx. 55 to 60%), but also diglycerides (38 to 42%) and monoglycerides (1 to 3%), which can facilitate micelle formation and absorption in the intestine.
• Effect of a meal on absorption: the authors note that discrepancies between different studies on EE bioavailability may result from the relationship between capsule consumption and a meal. Earlier studies (Lawson and Hughes) showed that EE absorption of EPA and DHA was significantly increased with simultaneous consumption of a fat-rich meal. In the study discussed, participants were advised but not instructed to take capsules "at meal times," without specifying fat content, which according to the authors may explain the observed lower bioavailability of EE.
• Fatty acid stereochemistry: the authors also tested whether the position of EPA and DHA in the acylglycerol particle (sn-1/3 vs sn-2) affects bioavailability. Their results indicate that the random arrangement of EPA and DHA in acylglycerols (as in the rTG preparation) has no negative effect on the absorption of long-chain omega-3 acids in humans.
• Final conclusions: the authors conclude that bioavailability may differ between commonly used types of fish oil concentrate preparations. rTG has higher bioavailability, EE may have lower bioavailability, FFA has intermediate bioavailability not differing from natural fish oil triglycerides. The stereoisomerism of n-3 PUFA in the glyceride particle does not affect the absorption of EPA and DHA in humans.