Several studies directly investigated the effect of fish oil on metabolic pathways that underlie muscle growth, with very interesting findings.
Supplementing healthy young and middle-aged (25-45 year old) men and women with 4g per day of fish oil concentrate, providing a daily dose of 1.86 g EPA and 1.5 g DHA – for 8 weeks was found to significantly increase the anabolic response of muscle protein synthesis to amino acids and insulin. The augmented anabolic response to amino acids and insulin was shown to be due to an increased activation of the mTOR/p70S6K signaling pathway, which is considered an integral control point for muscle protein anabolism and muscle cell growth.
Other mechanisms probably contribute as well. The same study showed that the fish oil supplementation doubled the proportion of EPA, DPA (another less well known omega-3 fatty acid) and DHA in muscle cell membranes, at the expense of omega-6 fatty acids and mono-unsaturated fatty acids, with no change in saturated fatty acid concentrations. Thus, it is possible that fish oil supplementation may influence anabolic signaling cascades by affecting membrane lipid composition and/or fluidity.
Fish oil supplementation also confers muscle anabolic effects in the elderly. The same research team conducted another study, using an identical research protocol (1.86 g EPA and 1.5 g DHA for 8 weeks), in healthy elderly subjects over 65 years (mean age 71 years). The results were the same as in the younger subjects; fish oil supplementation significantly increased the muscle protein synthetic response to amino acids and insulin. Thus, fish oil seems to attenuate the anabolic resistance to protein intake that develops with aging.
The researchers were so impressed with this response that they concluded high dose fish oil may be useful for both prevention and treatment of sarcopenia.Support for this comes from a study specifically demonstrating that fish oil increases anabolic signaling in aged muscles.
Both of these studies only measured the response of muscle protein synthesis to amino acids and insulin. Muscle mass, which is the result of a net positive muscle protein balance over a longer time period (at least 6 months), was not measured because the interventions lasted for only 8 weeks. However, taking into consideration that changes in muscle protein metabolism precede corresponding changes in muscle mass, these results are very promising.
Indeed, recently longer term outcomes of the fish oil supplementation study in elderly were published. Compared with the placebo group (which were given identical soft gels containing corn oil), supplementing healthy elderly subjects with 1.86 g EPA and 1.5 g DHA for 6 months significantly increased thigh muscle volume by 3.6%, handgrip strength by 2.3 kg (5.1 lb), 1-RM muscle strength by 4.0%. There was also a trending increase in power output by 5.6% in the fish oil group.
The difference in muscle volume between the fish oil and the placebo group at 6 mo was +3.5%, and the difference in overall muscle strength was +6%. This suggests that 6 month of fish oil supplementation can prevent 2-3 years of normal age-related losses in muscle mass (0.5–1.0%/year) and function (w2–3%/year). Thus, it was concluded that the fish oil fatty acids EPA and DHA may slow the common age-related decline in muscle mass and function in older adults, and that fish oil should be considered a therapeutic approach for preventing sarcopenia and maintaining physical independence in older adults.
Decreased Muscle Breakdown with Fish Oil