Omega-3 polyunsaturated fatty acid supplementation for muscle health in community-dwelling older adults at high risk of sarcopenia: protocol for a multicentre, randomised, double-blind, placebo-controlled trial.

The trial will enroll 400 community-dwelling older adults aged 60 years or older who are at high risk of sarcopenia.

• Eligibility criterion for sarcopenia risk is defined by handgrip strength <28 kg in men or <18 kg in women.
• Participants must be community-dwelling and aged 60 years or older.
• The study is multicentre in design.
• Total planned sample size is 400 participants.

Participants will be randomly allocated in a 1:1:1:1 ratio to one of four intervention groups for 6 months.

• The four groups are: (1) high eicosapentaenoic acid (EPA) group, (2) high docosahexaenoic acid (DHA) group, (3) high sn2-DHA group, and (4) corn oil control group.
• All intervention products will be packaged as capsules and administered at a daily dose of 2.5 g.
• The intervention duration is 6 months.
• The corn oil group serves as the placebo comparator.
• The design is double-blind.

The primary outcome of the trial is the change in handgrip strength from baseline.

• Handgrip strength was also used as the screening criterion for high sarcopenia risk at enrollment.
• Changes in handgrip strength will be compared across the three n-3 PUFA regimens and the placebo group.
• The study aims to investigate the efficacy of three different n-3 PUFA supplementation regimens compared with each other and with placebo.

Secondary outcomes include changes in skeletal muscle mass, physical function, inflammation- and metabolism-related blood biomarkers, and gut microbiota diversity.

• Skeletal muscle mass is assessed as a secondary outcome.
• Physical function is included as a secondary outcome measure.
• Blood biomarkers related to inflammation and metabolism will be measured.
• Gut microbiota diversity is included as a secondary outcome, reflecting interest in potential mechanistic pathways.

The trial was registered with the Chinese Clinical Trial Registry under number ChiCTR2500110506 and approved by the Ruijin Hospital Ethics Committee.

• Ethics approval was granted by the Ruijin Hospital Ethics Committee.
• The trial registration number is ChiCTR2500110506.
• Trial findings will be disseminated via publications in international peer-reviewed journals and presentations at relevant academic conferences.
• Study results will be made available to participants and the public on study completion.