Writing in Clinical Nutrition ESPEN, the team concludes that long-chain omega-3 fatty acids play a role in increasing lean body mass, skeletal muscle mass and quadriceps maximal voluntary capacity (MVC) - a measure of lower limb strength.
“The quadriceps is required for locomotion and may be more susceptible to wasting in the elderly,” writes the team that includes Dr Philip Calder, Head of Human Development & Health and Professor of Nutritional Immunology within Medicine at the University of Southampton.
“A reduction in muscle mass would parallel decreases in muscle strength of the quadriceps. Hence the effects of long-chain omega-3 fatty acids on muscle mass and quadriceps MVC are likely to be linked.”
The review consisted of a systematic review and meta-analysis of randomised controlled trials that used long-chain omega-3 fatty acids as an intervention with muscle-related endpoints.
A snowballing search was also used to identify additional studies that was completed on 23 April 2021.
The meta-analysis was conducted using meta-essentials worksheet, while bias was assessed using the Jadad scale.
In total, 119 articles were included in the qualitative assessment. After studies with endpoints in muscle fatigue, muscle quality and inflammation were removed, 66 articles were selected for meta-analysis.
Results revealed a significant relationship in favour of long-chain omega-3 fatty acid supplementation for lean body mass, skeletal muscle mass and quadriceps MVC.
Despite these observations the team could not find evidence of an expected dose response effect when increasing intake of long-chain omega-3 fatty acids.
“This may suggest that the threshold for an effect is reached by many studies, although it is more likely that the lack of a clear dose response effect reflects the heterogeneity between studies,” the study suggests.
Low-to-medium dose range
Other influences include the small number of studies reporting on any particular outcome, their varying duration, and the variations in relative amounts of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) used particularly in the low-to-medium dose range.
“The doses used in most studies were generally much higher than amounts recommended for cardiovascular disease prevention,” the study continues.
“However, the lack of clear dose effect may indicate that a low-dose supplement is sufficient to improve lean body mass.”
The paper’s discussion also points out that with higher intakes, EPA and DHA’s incorporation into white and red blood cells took longer and a new steady state would not be reached for many weeks to months.
The research team thought it plausible that significant effects of omega-3 LC PUFAs could be seen with a shorter supplementation time than 26 weeks, the threshold used in the previous meta-analysis.
All but six studies in the analysis supplemented for more than two weeks, and median study supplementation duration was 56 days.
The study was not without its limitations with the team conducting a meta-analysis based on published mean values.
“A more sensitive approach is to obtain individual subject data,” they explain. “This would also allow for the effect of inflammation markers or other potential confounders such as subject age, body weight or nutritional status on the muscle parameters to be taken into account.”
Further limitations include the decision to include a wide range of studies to identify potential associations across different muscle-related endpoints.
This meant that the researchers did not restrict studies based on number of subjects, patient populations, type of supplement used, dose, muscle fatigue or disuse procedures, or duration of supplementation, all of which may affect outcomes.
“As we excluded few studies and attempted to include as many datapoints as possible, our results are less likely to be affected by selection or publication bias,” they point out.
“On the other hand, the broad inclusion criteria may introduce greater variability and a lower likelihood of finding a significant result due to heterogeneity in study design and patient populations.”
Source: Clinical Nutrition ESPEN
Published online: doi.org/10.1016/j.clnesp.2021.10.011
“The effect of long chain omega-3 polyunsaturated fatty acids on muscle mass and function in sarcopenia: A scoping systematic review and meta-analysis.”
Authors: Julia Bird et al.