The trial was designed to test the effects of daily omega-3 pills on sarcopenia… the gradual loss of muscle mass and strength associated with aging.
To put things in perspective, a person in their 20s will have muscle that is up to 60 percent fat-free mass, while this proportion drops to less than 40 percent by age 70.
Almost one in two people over 65 suffer from sarcopenia to an extent that makes them noticeably frail and vulnerable to falls.
As the trial’s authors wrote, “A major cause for the loss of muscle mass with advanced age is the inability of aging muscle to adequately increase the rate of muscle protein synthesis in response to nutritional stimuli… e.g., amino acids and insulin” (Smith GI et al. 2011).
These facts may have prompted the test of omega-3s, which influence the body’s production and use of insulin.
For example, two rat studies found that dietary omega-3s increase the extent to which insulin binds to muscle cell membranes and the efficiency with which muscle cells use blood sugar (Storlien LH et al. 1991; Liu S et al. 1994).
Pilot trial is first to link omega-3s to reduced sarcopenia risk
To test whether omega-3s might help keep muscle mass from melting away, a Washington University team recruited 16 healthy adults (average age 71) and randomly assigned them to receive either omega-3 fish oil supplements or corn oil placebo capsules for eight weeks (Smith GI et al. 2011).
The study, led by Bettina Mittendorfer, Ph.D., tested the effects of taking four grams of fish oil per day, providing 1.86 grams of omega-3 EPA plus 1.5 grams of omega-3 DHA.
The authors chose this dose because it is the level approved by the Food and Drug Administration for lowering blood triglyceride levels in heart patients. (It’s higher than the daily dose range recommended for the general public—250mg to 500mg per day—but there is no evidence that this amount of omega-3s is unsafe for healthy people.)
Unlike the corn oil group, the omega-3 group had twice as much anabolic (muscle building) activity resulting from two key pathways known to increase lean muscle mass.
As Dr. Mittendorfer and her co-workers wrote, “Omega-3 fatty acids stimulate muscle protein synthesis in older adults and may be useful for the prevention and treatment of sarcopenia.”
And they pinpointed one way in which the omega-3s helped: “In the present study, we provide novel evidence that dietary omega-3 fatty acid supplementation augments the hyperaminoacidemia- and hyperinsulinemia-induced increase in the rate of muscle protein synthesis in older adults” (Smith GI et al. 2011).
What does this jargon mean?
Hyperaminoacidemia-induced muscle building results from high levels of amino acids in the blood (Young VR, Marchini JS 1990)—due to protein-rich diets—while hyperinsulinemia–induced muscle building results when blood insulin levels are high (Fryburg DA et al. 1995; Hillier TA et al. 1998).
As a possible explanation for these increases in these two anabolic (muscle-building) pathways, the omega-3 group showed increases in the activation of a “signaling” pathway that’s reported to be, as the authors wrote, an “…integral control point for muscle cell growth” (specifically, a pathway called mTOR-p70s6k).
Still, the full range of means by which the omega-3s may enhance muscle mass creation remains to be detailed.
Clavel S, Farout L, Briand M, Briand Y, Jouanel P. Effect of endurance training and/or fish oil supplemented diet on cytoplasmic fatty acid binding protein in rat skeletal muscles and heart. Eur J Appl Physiol. 2002 Jul;87(3):193-201. Epub 2002 Apr 26.
Fryburg DA, Jahn LA, Hill SA, Oliveras DM, Barrett EJ. Insulin and insulin-like growth factor-I enhance human skeletal muscle protein anabolism during hyperaminoacidemia by different mechanisms. J Clin Invest. 1995 Oct;96(4):1722-9.
Hillier TA, Fryburg DA, Jahn LA, Barrett EJ. Extreme hyperinsulinemia unmasks insulin's effect to stimulate protein synthesis in the human forearm. Am J Physiol. 1998 Jun;274(6 Pt 1):E1067-74.
Liu S, Baracos VE, Quinney HA, Clandinin MT. Dietary omega-3 and polyunsaturated fatty acids modify fatty acyl composition and insulin binding in skeletal-muscle sarcolemma. Biochem J. 1994 May 1;299 ( Pt 3):831-7.
Smith GI, Atherton P, Reeds DN, Mohammed BS, Rankin D, Rennie MJ, Mittendorfer B. Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis in older adults: a randomized controlled trial. Am J Clin Nutr. 2011 Feb;93(2):402-12. Epub 2010 Dec 15.
Sohal PS, Baracos VE, Clandinin MT. Dietary omega 3 fatty acid alters prostaglandin synthesis, glucose transport and protein turnover in skeletal muscle of healthy and diabetic rats. Biochem J. 1992 Sep 1;286 ( Pt 2):405-11.
Storlien LH, Jenkins AB, Chisholm DJ, Pascoe WS, Khouri S, Kraegen EW. Influence of dietary fat composition on development of insulin resistance in rats. Relationship to muscle triglyceride and omega-3 fatty acids in muscle phospholipid. Diabetes. 1991 Feb;40(2):280-9.
Young VR, Marchini JS. Mechanisms and nutritional significance of metabolic responses to altered intakes of protein and amino acids, with reference to nutritional adaptation in humans. Am J Clin Nutr 1990;51:270-89