Omega-3s and muscle: what the studies really say
Omega-3 fatty acids are credited with the power to help build muscle and recover better. Studies give a clearer answer than expected, and it depends mostly on your age: in healthy young adults, neither more muscle nor more strength ; after 55, a small gain in strength and function ; and on soreness, a measurable effect but too weak for you to feel it.
In young adults: meta-analyses find nothing
The most recent meta-analysis, published in 2026, includes only healthy adults without obesity. Out of four trials for lean mass and eight for strength, it finds no clear effect compared to placebo: a standardized mean difference of 0.26 for lean mass, with a range going from −1.14 to 1.66, and −0.02 for strength. Its authors conclude that the evidence does not allow us to say that omega-3s improve either.
The mechanism does not support it either. A 2025 meta-analysis on muscle protein synthesis finds no effect of omega-3s on this rate (six studies, standardized mean difference 0.03). In 20 young men, 5 g of fish oil per day for eight weeks changed nothing in myofibrillar protein synthesis after a training session and protein intake — even though some cellular markers of anabolism were lower.
One trial is an exception. In 21 young adults followed for ten weeks of resistance training, lean mass progressed similarly with or without fish oil (+3.4% versus +2.4%, non-significant difference), but bench press strength progressed more with fish oil (+17.7% versus +9.7%). A 21-person trial versus a meta-analysis pooling eight trials on strength: the meta-analysis carries more weight.
Healthy adults: 8 trials (2026 meta-analysis) ; 55 and older: lower-body strength (2022 meta-analysis)
After 55: a little extra strength and function
In older individuals, the signal exists. A 2022 meta-analysis of 16 studies in people aged 55 and older finds no effect on lean mass, but a gain in lower-body strength (standardized mean difference 0.54) and on everyday life tests: about two more chair stands in 30 seconds. Another meta-analysis, on ten articles, finds a slight muscle mass gain (0.33 kg), which rises to 0.67 kg beyond 2 g of omega-3s per day.
A six-month trial points in this direction. In 60 people aged 60 to 85, six months of fish oil increased thigh muscle volume (+3.6%), grip strength (+2.3 kg) and maximal strength (+4.0%) compared to the control group, with no added training. Combined with resistance training, omega-3s also improved strength gains in 45 women aged 64 (2 g per day) and in 34 sarcopenic elderly women (4 g per day: +19.5 Nm of peak torque versus +5.7 Nm under placebo). In this last trial, the quadriceps cross-sectional area did not progress further.
But not in all trials
Dose could matter: the large negative trial provided about 1 g per day, the positive trials in older women 2 and 4 g, and the meta-analysis cited above sees more muscle mass beyond 2 g. But the trial in men aged 65 and older, at 3 g, found nothing either, and no trial compared doses head-to-head: it is a lead, not a rule.
When the muscle is immobilized
In 20 young women whose leg was immobilized for two weeks, 5 g of omega-3s per day reduced muscle wasting: −8% volume versus −14% in the control group. After resumption, the omega-3 group's volume had returned to its starting level, unlike the control group. A single trial on 20 people — but it is the clearest result in young subjects.
In 16 older individuals, eight weeks of omega-3s did not change resting muscle protein synthesis, but increased its response to an amino acid and insulin supply. This is a laboratory measurement, not a muscle gain; the 2025 meta-analysis cited above, which pools this type of measurement, finds no overall effect.
Even on a diet: in 20 trained young men in caloric restriction, the loss of lean mass was the same with or without 4 g of omega-3s per day (−1.4 kg versus −1.2 kg).
Soreness: real, but too small to feel
A meta-analysis of twelve randomized trials finds significantly less soreness after eccentric exercise with omega-3s: −0.93 points on a 10-point scale. But the threshold at which a person feels the difference is 1.4 points. The authors therefore conclude, with low-quality evidence, to a drop that is not clinically important, and with no effect on strength or mobility. Another meta-analysis finds a drop in blood markers of muscle damage (creatine kinase, LDH, myoglobin) — laboratory figures, not a sensation.
Isolated trials are divided. For: in 27 untrained men, 1.8 g per day reduced pain at 48 hours; in 20 professional rugby players in pre-season, an omega-3-enriched protein supplement limited soreness and maintained vertical jump (+4.6% versus −3.4%). Against: in 16 trained young men, 5 g per day for four weeks changed neither creatine kinase, nor soreness, nor strength for three days; in 30 young women, nothing either on pain or strength.
| What you are looking for | What the studies say |
|---|---|
| More muscle, young adult | No: no clear effect on lean mass (2026 meta-analysis) |
| More strength, young adult | No in the meta-analysis of eight trials; one isolated trial says yes |
| Strength and function after 55 | A modest gain, especially the lower body, at 2 g/day and above |
| Muscle mass after 55 | A slight gain in one meta-analysis, none in another |
| Less wasting during immobilization | Yes in a 20-person trial, at 5 g/day |
| Less delayed onset muscle soreness | A real effect, but below the threshold you can feel |
Forms, doses, precautions, and the studies on the supplement profile — what omega-3s do outside the muscle.
See the omega-3 supplement profileEvery figure in this article comes from a study you can open: underlined mentions lead to the summary of the work it is drawn from, written solely from the abstract. Several trials involve small sample sizes, and the meta-analyses on soreness themselves judge their evidence to be of low quality. Informative content, which does not replace the advice of a healthcare professional.