The Impact of n-3 Polyunsaturated Fatty Acids on Muscle Mass, Strength, and Physical Function in Older Adults: An Umbrella Review

Background: Population aging is accelerating worldwide, making sarcopenia an increasingly important public health concern. Currently, effective and widely accepted interventions remain limited. This umbrella review aimed to examine the effects of n-3 polyunsaturated fatty acid (n-3 PUFA) supplementation on sarcopenia-related outcomes and to inform clinical decision-making and future research. Method: A comprehensive literature search was performed in PubMed, Web of Science, EBSCO, and ScienceDirect to identify randomized controlled trials (RCTs) and meta-analyses of RCTs evaluating the effects of n-3 PUFA supplementation on muscle-related outcomes in adults aged ≥55 years. Primary outcomes included skeletal muscle mass, muscle strength, and physical function. The methodological quality of the included meta-analyses was assessed using A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2), and the certainty of the evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. In addition, the corrected covered area (CCA) was used to assess the degree of overlap among primary studies included in the systematic reviews. A random-effects model was applied to estimate the pooled effect sizes, standardized mean differences (SMDs), and 95% confidence intervals. Results: A total of seven RCTs and seven meta-analyses met the inclusion criteria. The interventions involved the administration of n-3 PUFAs through diet or supplementation, with most studies applying mixtures rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and a few using flaxseed oil rich in alpha-linolenic acid (ALA). The n-3 PUFA dosage ranged from 1.3 g/day to 14 g/day, and intervention duration ranged from 6 weeks to 6 months. Overall, n-3 PUFA supplementation was associated with a modest but measurable increase in muscle strength and showed potential benefits for lower-limb physical performance and muscle mass. However, a high degree of overlap among primary studies was observed (CCA = 14.02%), indicating substantial redundancy in the evidence base. Moreover, the certainty of the evidence ranged from moderate to very low. While moderate certainty was observed for some outcomes (e.g., lower body strength, lower-extremity physical function), most muscle strength and function outcomes, including grip strength, walking speed, and upper body strength, were rated as low or very low certainty, largely due to the limited number of trials and methodological constraints. Conclusion: In summary, n-3 PUFA supplementation, particularly marine-derived n-3 PUFAs, may offer preliminary benefits in attenuating age-related declines in muscle mass and function among healthy older adults. However, given the predominantly low-to-very-low certainty of the evidence and the high degree of overlap among primary studies, the overall reliability of the findings may be compromised. Therefore, large-scale, methodologically rigorous, and high-quality RCTs are urgently needed to validate these preliminary findings and establish evidence-based clinical guidelines for the use of n-3 PUFAs in the prevention and management of sarcopenia. The PROSPERO Registration: CRD420251165901 (https://www.crd.york.ac.uk/PROSPERO/view/CRD420251165901).