A changed biomarker was not a faster 1,500 metres
Twenty-six amateur male long-distance runners aged at least 29 took omega-3 or placebo capsules during 12 weeks of endurance training. The omega-3 group increased its omega-3 index and the abstract reports changes in some laboratory performance measures. The intervention did not improve the 1,500-metre run time.
That split matters. A biomarker, VO2peak, or running-economy signal is not automatically a race-performance result. The small male sample, concurrent training, specific supplement dose, short race test, and pooled correlation analysis limit what can be inferred for other runners or distances. Review the exact groups and outcomes in the PubMed record and open full text.
For a supported running goal, do not add this supplement simply to chase a laboratory number. First identify the actual training or nutrition problem, protect the basics of food quality, energy availability, sleep, and consistent training, and use a qualified clinician or sports dietitian when supplementation, health conditions, pregnancy, medication, or adverse effects make the decision uncertain. Do not copy the study dose without individual guidance.