There are many claims now that omega-3 fatty acids can optimise muscle building. But what are the claims based on? is there evidence?
The theory that fish oil improves muscle building
The idea of omega-3 polyunsaturated fatty acids - omega-3s for short -, promoting muscle growth in strength/power-based athletes gains momentum year-on-year (1). Fueling this idea is the scientific discovery that, once digested, a proportion of omega-3s enter skeletal muscle tissue, and settle in what is called the outer phospholipid membrane space of the muscle cell (2). More recently, evidence emerged that omega-3s act to “switch on” the muscle’s built-in machinery that controls muscle protein synthesis. Omega-3s would thus turn on protein synthesis. But, how strong is the existing scientific evidence to support omega-3s conferring an “anabolic advantage” in athletes?
mTOR and muscle protein synthesis
The scientific term ‘muscle protein synthesis’ — or MPS for short — is no stranger to the strength/power-based athlete with the goal to increase muscle mass. In theory, the higher the rate of MPS, the greater the potential to accumulate new (and functional) muscle proteins, ultimately resulting in increased muscle mass and strength. Rates of MPS are controlled by the activity of proteins that make up the mTOR pathway — or mechanistic target of rapamycin to be long-winded (3)! These proteins are housed within the muscle cell itself. Sports nutrition strategies aimed at triggering the mTOR pathway and maximising MPS rates in response to resistance exercise have, of course, focused on best protein nutrition practice (4). Yet, a topic of recent interest concerns the nutrients, including fats, that should be ingested alongside protein to maximise the muscle anabolic response.
Omega-3s increase anabolic effects?
The potential “muscle anabolic action” of omega-3s was initially sparked by two studies published in 2011 by Smith and colleagues (5, 6). These studies were conducted in untrained men and women and measured MPS rates under basal (i.e., fasted and rested) and “fed” (amino acids and insulin were infused into the blood via a forearm vein to mimic ingestion of a protein-rich meal) conditions before and after 8 weeks of fish oil (4 grams per day) derived omega-3 supplementation. Whereas the basal response of MPS was similar between fish oil and control (corn oil) supplementation groups, the response of MPS to “feeding” was enhanced by 30–60% in the fish oil group. So, in effect, omega-3s showed potential to enhance the MPS response to the “anabolic” nutrients (amino acids and insulin) contained in a typical meal.
So, in effect, omega-3s showed potential to enhance the MPS response to the “anabolic” nutrients (amino acids and insulin) contained in a typical meal.
Study showed no effect of omega-3s on muscle protein synthesis
We recently investigated the anabolic potential of omega-3s using a study design set up to mimic the nutrition and training practices of elite athletes (7). In this study, trained volunteers ingested a 30-gram dose of whey protein immediately post resistance exercise workout. We administered a high dose (5 grams per day) fish oil supplementation protocol over 8 weeks that was rich in the omega-3 species, eicosapentaenoic acid or EPA for short.
To our surprise, fish oil supplementation failed to increase the MPS response to the post workout ingestion of whey protein (7). So, when ingesting a protein dose known to stimulate a maximal response of MPS (8), omega-3 supplementation did not confer any muscle anabolic advantage.
When ingesting a protein dose known to stimulate a maximal response of muscle protein synthesis, omega-3 supplementation did not confer any muscle anabolic advantage.
It is conceivable that the 30 gram whey protein dose administered in this study “saturated” the muscle protein synthetic machinery (8). Therefore, future research is warranted to investigate the influence of omega-3s on the response of MPS to ingesting a suboptimal (10-15 gram) protein dose post workout. But for now, in terms of applied practice, the scientific evidence supporting a role for omega-3s in promoting MPS in athletes is weak, at least if the athlete follows recommended sports nutrition guidelines to support muscle building (9), e.g., a positive energy balance and sufficient dietary protein intake.
Philpott, J.D., Witard, O.C., and Galloway, S.D.R. (2019). Applications of omega-3 polyunsaturated fatty acid supplementation for sport performance. Res. Sports Med. 27(2), 219-237.
McGlory, C., Galloway, S.D., Hamilton, D.L., McClintock, C., Breen, L., Dick, J.R., Bell, J.G., and Tipton, K.D. (2014). Temporal changes in human skeletal muscle and blood lipid composition with fish oil supplementation.Prostaglandins Leukot.Essent.Fatty Acids 90199-206.
Kimball, S.R., Horetsky, R.L., and Jefferson, L.S. (1998). Signal transduction pathways involved in the regulation of protein synthesis by insulin in L6 myoblasts. Am. J. Physiol. 274C221-C228.
Witard, O.C., Wardle, S.L., Macnaughton, L.S., Hodgson, A.B., and Tipton, K.D. (2016). Protein Considerations for Optimising Skeletal Muscle Mass in Healthy Young and Older Adults. Nutrients 8(4), 10.3390/nu8040181.
Smith, G.I., Atherton, P., Reeds, D.N., Mohammed, B.S., Rankin, D., Rennie, M.J., and Mittendorfer, B. (2011). Omega-3 polyunsaturated fatty acids augment the muscle protein anabolic response to hyperinsulinaemia-hyperaminoacidaemia in healthy young and middle-aged men and women. Clin. Sci. 121267-278.
Smith, G.I., Atherton, P., Reeds, D.N., Mohammed, B.S., Rankin, D., Rennie, M.J., and Mittendorfer, B. (2011). Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis in older adults: a randomized controlled trial. Am.J.Clin.Nutr. 93402-412.
McGlory, C., Wardle, S.L., Macnaughton, L.S., Witard, O.C., Scott, F., Dick, J., Bell, J.G., Phillips, S.M., Galloway, S.D., Hamilton, D.L., and Tipton, K.D. (2016). Fish oil supplementation suppresses resistance exercise and feeding-induced increases in anabolic signaling without affecting myofibrillar protein synthesis in young men. Physiol. Rep. 4(6), 10.14814/phy2.12715.
Witard, O.C., Jackman, S.R., Breen, L., Smith, K., Selby, A., and Tipton, K.D. (2014). Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. Am.J.Clin.Nutr. 9986-95.
Witard, O.C., Garthe, I., and Phillips, S.M. (2019). Dietary Protein for Training Adaptation and Body Composition Manipulation in Track and Field Athletes. Int. J. Sport Nutr. Exerc. Metab. 29(2), 165-174.