For adults over 60, the omega-3 fats in fish oil may do more than support the heart. A randomized controlled trial led by Gordon Smith at Washington University in St. Louis, published in the American Journal of Clinical Nutrition, found that eight weeks of EPA and DHA supplementation enhanced the muscle protein synthesis response triggered by amino acids and insulin in healthy older adults.
The response is what tells muscle to rebuild after a meal or a workout. When it weakens with age, muscle loss, known as sarcopenia, accelerates, especially during periods of illness or bed rest.
Smith and colleagues used 4 grams a day of combined EPA and DHA against a corn oil placebo in 16 adults aged 65 to 84. They also saw greater activation of proteins in the mTOR signaling pathway, the cellular switch that flips muscle into rebuild mode. Their conclusion was that the supplements may be useful for preventing and treating sarcopenia.
A larger trial measured real muscle gains
A follow-up trial from the same team, published in 2015, ran for six months in 60 healthy adults aged 60 to 85. Participants took 1.86 grams of EPA and 1.50 grams of DHA a day, delivered as the prescription fish oil Lovaza.
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Thigh muscle volume rose 3.6 percent compared with the corn-oil group. Handgrip strength climbed by an average of 2.3 kilograms, and one-repetition maximum strength gained 4 percent. The authors described fish oil as a therapy that slows the normal decline in muscle mass and function in older adults.
The picture has grown more nuanced
Not every follow-up has been as clean. A systematic review and meta-analysis covering 16 trials and 2,438 older adults, published in 2022, found that omega-3 supplementation improved lower-body strength and functional tests such as the timed-up-and-go, yet did not increase lean body mass on its own.
A more recent meta-analysis in Nutrition Reviews, pooling 8 trials with 188 participants, found no significant effect on the direct rate of muscle protein synthesis. Whole-body protein synthesis, however, did rise. Reviewers now describe the mTOR mechanism first proposed by Smith as uncertain, even as strength and functional benefits keep showing up.
A 2024 review points to a floor of roughly 500 milligrams of EPA plus DHA a day for general prevention, with muscle strength benefits typically emerging above 2 grams a day when supplementation runs for at least six months.
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Food first, then supplements
The National Center for Complementary and Integrative Health notes that EPA and DHA are concentrated in cold-water fish such as salmon, mackerel, and tuna. Federal dietary guidance suggests adults eat at least 8 ounces of seafood a week.
Plant sources such as flaxseed, walnuts, and chia seeds provide ALA, a shorter-chain omega-3. The body converts very little of it into EPA and DHA, which is one reason marine sources carry the strongest muscle evidence.
Side effects of fish oil capsules are usually mild and include a fishy aftertaste, heartburn, and loose stools. Higher doses can also thin the blood, so anyone taking anticoagulants or preparing for surgery should talk to their doctor before starting a supplement.
Omega-3 is not a substitute for resistance training or adequate dietary protein, which remain the two strongest tools against age-related muscle loss. But for older adults who already take fish oil for heart or joint reasons, the muscle-preservation angle is a genuine second benefit backed by trial evidence rather than marketing.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.