The Impact of Omega-3 Fatty Acid Supplementation on the Composition of Erythrocyte Membranes in Athletes

Skeletal muscle function, including the ability to generate force, sustain repeated high-intensity efforts, and resist fatigue, is essential for soccer performance. In addition to neuromuscular adaptations, increasing evidence suggests that nutritional interventions, particularly omega-3 fatty acid supplementation, may influence muscle function, recovery, inflammation, and cognitive performance. However, despite growing interest in omega-3 fatty acids, evidence regarding their effects on physical and cognitive performance in competitive soccer players remains limited.

The present randomized, placebo-controlled trial aims to evaluate the effects of four weeks of high-dose omega-3 fatty acid supplementation in competitive male soccer players aged 16 to 35 years. Participants will continue their regular soccer training and maintain their habitual mixed diet throughout the study.

The primary objective is to determine the effects of supplementation on the Omega-3 Index and the erythrocyte fatty acid profile, including omega-3, omega-6, trans fatty acids, and arachidonic acid (AA). In addition, the study will evaluate changes in cognitive function, hormonal profile, speed and endurance performance, hematological parameters, lipid profile, inflammatory markers, oxidative-antioxidant status, and erythrocyte membrane composition.

The fatty acid profile will be assessed using a validated laboratory method that enables quantitative determination of individual fatty acids in erythrocyte membranes, providing an objective biomarker of long-term omega-3 status and membrane lipid composition. This approach allows comprehensive evaluation of the biological response to omega-3 supplementation in competitive athletes.

The findings of this study are expected to improve understanding of the physiological effects of high-dose omega-3 fatty acid supplementation in soccer players and may contribute to evidence-based nutritional strategies aimed at optimizing health, recovery, cognitive function, and athletic performance.

**Inclusion Criteria:**

• Male competitive soccer players aged 16-35 years.
• Regular participation in organized soccer training and competition.
• A minimum of 6 years of systematic soccer training experience.
• Participation in regular team training during the study period.
• Habitual mixed diet.
• Ability and willingness to maintain usual dietary habits and training load throughout the 4-week intervention.
• Written informed consent provided by the participant.
• For participants under 18 years of age, written informed consent provided by a parent or legal guardian and assent provided by the participant.

**Exclusion Criteria:**

• Current use of omega-3 fatty acid supplements or fish-oil products.
• Use of omega-3 supplements within the 3 months preceding enrollment.
• Known allergy or hypersensitivity to fish, seafood, fish oil, or any ingredient of the study supplements.
• Diagnosed cardiovascular, metabolic, endocrine, gastrointestinal, neurological, inflammatory, autoimmune, or hematological disease.
• Acute infection, injury, or illness that could affect participation in training or study assessments.
• Use of medications or dietary supplements that could influence lipid metabolism, inflammatory status, hormonal profile, blood coagulation, cognitive function, or physical performance.
• Regular use of anticoagulant or antiplatelet medication.
• Significant change in diet, training volume, or supplementation during the study period.
• Failure to comply with the supplementation protocol or attendance requirements.
• Participation in another clinical or nutritional intervention study during the study period.