Taking fish oil supplements containing EPA and DHA may lead to very small or negligible gains in muscle size and strength for most people, and these changes are not large enough to be meaningful in a clinical or practical sense.
Evidence from Studies
Supporting (3)
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Long-Chain Omega-3 Fatty Acid Supplementation and Exercise-Induced Muscle Damage: EPA or DHA?
Taking fish oil supplements helped people recover their muscle strength a bit faster after intense exercise, but the improvement was very small and not big enough to matter much in real life.
Effects of eight weeks of eicosapentaenoic acid and medium-chain triacylglycerol structured lipid intake on EPA/AA ratio and muscle performance in young men
This study gave people fish oil supplements for eight weeks and found no real improvement in muscle strength or endurance, even though their blood markers changed. That supports the idea that fish oil doesn’t make you significantly stronger or bigger.
Nutritional Supplements for Muscle Hypertrophy: Mechanisms and Morphology—Focused Evidence
Fish oil supplements like EPA and DHA might help you recover better after workouts, but they don’t really make your muscles bigger or stronger in a meaningful way.
Contradicting (1)
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The Role of Omega-3 Polyunsaturated Fatty Acids on Sarcopenia and Aging Muscle
This study found that fish oil supplements can help older people keep and even build muscle strength, especially when they also do strength training — which is more than just a tiny benefit. That means the claim saying fish oil doesn’t really help is wrong.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.