Three grams of fish oil per day for 18 weeks in combination with resistance training produced a 18% improvement in maximal isokinetic torque and muscle quality in older women compared to placebo, according to data published in the American Journal of Clinical Nutrition.
“[W]e have demonstrated for the first time to our knowledge that 3 g long chain n-3 PUFAs/d enhances the resistance exercise training-induced increases in muscle quality and maximal isometric torque in older women but not older men. The findings of a benefit in women are of particular importance because women live longer than men and, because of their lower starting strength, cross the disability threshold earlier,” wrote the authors, led by Mariasole Da Boit from the University of Aberdeen in Scotland.
The likelihood of clinically meaningful results
Commenting independently on the study, Harry Rice, PhD, VP of regulatory & scientific affairs for the Global Organization for EPA and DHA Omega-3s (GOED), told us: “Given the loss of muscle function inherent to aging, the results may translate into prolonged independence and quality of life. Many elderly individuals are prescribed physical therapy, so it's not out of the question to think that omega-3 supplementation could increase the likelihood and maintenance of clinically meaningful results.
“As far as the demonstrated benefits being limited to women, I think there's a good chance the study was under-powered for men. Further research in this area will be revealing.”
The researchers recruited 50 men and women with an average age of 70 to participate in their randomized, double-blind, placebo-controlled trial. Participants were randomly assigned to receive either fish oil (three grams per day, providing 2.1 g EPA and 0.6 g DHA, by Barleans) or placebo (safflower oil, also by Barleans) for 18 weeks in combination with resistance exercise training.
Results showed that maximal isometric torque, a measure of muscle function, increased by 34% in women receiving the fish oil supplements, compared with only 16% in women receiving placebo. No such differences were observed in the male participants.
In addition, muscle quality improved by 27% in women in the fish oil group, versus a 9% improvement in women receiving placebo. Again, no such benefits were observed in the men.
Omega-3 supplementation did significantly reduce triglyceride concentrations in both sexes, versus placebo, but no changes were observed for glucose, insulin, or inflammatory markers, wrote the researchers.
“It has been proposed that these sex differences could be attributed to differences in the enrichment of long-chain n–3 PUFAs into cell membranes,” wrote the researchers. “Previous work has shown, at the same dose of long-chain n–3 PUFAs, a greater EPA and total long-chain n–3 PUFA enrichment in plasma phosphatidylcholine in women after fish oil supplementation (8 wk with 0.7 g EPA/DHA or 1.8 g EPA/ DHA). However, in our study, the postsupplementation concentration of erythrocyte and muscle EPA and DHA was not different between men and women, although the variability was large.
“Another factor that potentially influenced our findings is a difference in nutritional intake between groups,” they added. “[O]lder women do not increase muscle strength to the same magnitude as older men. It may be possible that longchain n–3 PUFAs only have effects in women because there is a greater capacity for improvement; i.e., their normal response is suboptimal compared with men. This would make women more amenable to the effects of long-chain n–3 PUFAs. These mechanisms proposed are currently speculative, and further work is clearly needed to investigate them.”
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.116.140780
“Sex differences in the effect of fish oil supplementation on the adaptive response to resistance exercise training in older people: a randomized control trial”
Authors: M. Da Boit, et al.