The effects of n-3 fatty acids on muscle function in older adults

This thesis examines the effects of n-3 fatty acid supplementation on muscle health in older adults through a systematic review and meta-analysis, a cross-sectional analysis, and a randomised controlled trial. Sarcopenia, characterised by the progressive decline in muscle mass and strength with ageing, is recognised as a major global health challenge. There is increasing scientific interest in long-chain n-3 polyunsaturated fatty acids (LCn-3 PUFA) as a potential intervention to prevent or treat sarcopenia. This thesis aimed to examine the effects of LCn-3 PUFA supplementation on muscle health in older adults through three studies: 1) a systematic review and meta-analysis, 2) a cross-sectional analysis of the association of dietary n-3 fatty acid intake with muscle outcomes, and 3) a randomised controlled trial (RCT) comparing the effects of krill oil and fish oil supplementation on muscle strength, size and physical function. Chapter 2 found, in five RCTs (n=488; 348 females, 140 males), no effect of LCn-3 PUFA on grip strength (SMD 0.57, 95% CI [−0.10, 1.25]; p=0.10) with substantial heterogeneity (I²=90%). Chapter 3 used UK Biobank data from 61,381 (28,187 men, 33,194 women) older adults (≥60 years) and found that higher n-3 intake was associated with higher grip strength in both men (0.114 kg; 95% CI: 0.02 to 0.21) and women (0.115 kg; 95% CI: 0.05 to 0.18), with no associations for muscle mass index. Chapter 4 found that fish oil supplementation improved knee extensor strength by 11.6 Nm (95% CI, 0.5 to 22.7, p=0.01) and handgrip strength by 2.2 kg (95% CI, 0.2 to 4.2, p=0.007), compared to placebo, while both krill and fish oil enhanced gait parameters, for example cadence improved by 5.3 steps/min (95% CI, 1.2 to 9.4, p = 0.00) with fish oil and 4.0 steps/min 95% CI, 0.1 to 8.0, p = 0.01) with krill oil. In conclusion this thesis provides substantial evidence that marine-derived LCn-3 PUFA supplementation represents an effective and safe intervention for supporting muscle health in older adults.