Health and fitness aficionados often take fish oil to optimize their heart, brain, and joint health.

Research shows this is a worthwhile gambit—fish oil is effective on all these fronts.

However, emerging research indicates another significant reason for weightlifters to consider fish oil: it could enhance muscle and strength gain.

This is because the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oil appear to boost muscle protein synthesis (MPS), creating a more “anabolic” environment in your body.

For example, studies published in the journals Clinical science (London, England : 1979) and Physiological Reports suggest fish oil supplementation can increase MPS by ~30-to-50%.

Some research also suggests that fish oil impacts muscle fiber type, neuromuscular recruitment, muscle protein breakdown rates, and insulin signaling—mechanisms that could further enhance muscle and strength gains.

While these arguments are intriguing, results from studies on fish oil’s actual impact on muscle growth and strength gain tend to be inconsistent. 

That said, most of the studies conducted so far have glaring methodological flaws, which makes it difficult to know whether the variable results are a reflection of fish oil’s efficacy, or whether the findings are skewed by sloppy science.

This ambiguity prompted researchers at Baylor University to undertake their own research. Their goal was to investigate whether fish oil improves body composition and strength in a well-conducted trial.

They split 21 men and women into two groups. One group took 4.5 g of fish oil daily (~2.3 g of EPA and ~1.6 g of DHA) and the other took a placebo for 10 weeks. This is about 2-to-3 times more fish oil than the generally recommended dose for maintaining optimal health (~1-to-2 g per day of EPA and DHA combined). 

During the study, participants trained 3 times weekly on non-consecutive days, doing 3-to-4 sets of the squat, leg press, leg extension or leg curl, bench press, shoulder press, seated cable row, and lat pulldown in each workout. 

The results showed that the fish oil group experienced larger increases in their bench press one-rep max (~24 lb. vs. ~14 lb.) and squat one-rep max (~53 lb. vs 41 lb.). They also tended to lose slightly more fat and gain marginally more lean body mass (a proxy for muscle) than the placebo group, though the differences were small.

While these findings might not be astounding, they suggest fish oil is a win-win for weightlifters: it certainly boosts health, likely improves performance, and may help you build muscle and lose fat faster. 

Before we get too excited, though, there are a couple of riders to consider. 

First, while this was a well-conducted study with clear results favoring fish oil, it’s still not enough evidence to draw any firm conclusions about how fish oil affects strength gain, muscle growth, and fat loss.

As such, it’s sensible to think of fish oil as having “potential” rather than “proven” benefits for performance and body composition, at least until we have more high-quality evidence to go off. 

Second, the results suggest that you have to take a large daily dose to get these potential benefits, which may increase your risk of developing cardiovascular issues according to some research.

That said, many experts are skeptical that this is something we should worry about, since science is still yet to puzzle out the connection between high daily doses of fish oil and the potential risk of cardiovascular problems. 

Still, until there’s more long-term research on the health effects of taking large doses of fish oil daily, it’s wise to stick to what’s proven to be effective and safe, which most research suggests is a combined intake of ~1.8 g of EPA and DHA per day for general health, or up to ~3 g per day to reduce muscle soreness. 

If you’d like a 100% natural high-potency reesterified triglyceride fish oil made from deep-water Peruvian anchovies and sardines that contains 2.4 g of EPA and DHA per serving, check out Triton.

(Or if you aren’t sure if Triton is right for you, take the Legion Supplement Finder Quiz! In less than a minute, it’ll tell you exactly what supplements are right for you. Click here to check it out.)

Takeaway: Taking fish oil daily may boost strength gain and modestly improve your ability to build muscle and lose fat, but there’s still very little evidence to say this is the case.

This article is part of our Research Review series, which explores a scientific study on diet, exercise, supplementation, mindset, or lifestyle that will help you gain muscle and strength, lose fat, perform and feel better, live longer, and get and stay healthier. 

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