Krill oil (KO) is a natural source of long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA), predominantly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), delivered in phospholipid form alongside the antioxidant astaxanthin, and may support recovery from exercise-induced muscle damage (EIMD) (1). In this double-blind, randomised, placebo-controlled, parallel-group trial, 30 healthy untrained adults (placebo, n = 15: 6F/9M; KO, n = 15: 8F/7M) consumed 4 g/day KO or matched placebo (PLA) for ≥8 weeks to examine effects on the omega-3 index (O3I), body composition, sleep quality and EIMD recovery. The omega-3 index (O3I) and whole-blood fatty acid profile were derived from dried blood spots at baseline and post-supplementation, to determine changes in omega-3 status and confirm compliance. Body composition (dual-energy X-ray absorptiometry) and sleep quality (Pittsburgh Sleep Quality Index) were also assessed at these timepoints. Pain, pressure-pain threshold, muscle thickness, isometric and isokinetic peak torque, creatine kinase (CK) and lactate dehydrogenase (LDH) were assessed before, immediately after and 48 h following an eccentric EIMD protocol. KO increased O3I from 4.52 ± 0.42% to 6.67 ± 1.73%, compared with 4.65 ± 0.51% to 4.85 ± 0.46% in PLA (adjusted difference 1.72 percentage points; 95% CI 0.75 to 2.68; p = 0.001), with corresponding increases in total n-3, EPA, docosapentaenoic acid n-3 (DPA n-3), and DHA and decreases in Arachidonic acid (AA) and omega-6 (n-6) ratios. No significant effects of KO were observed for body composition (all p ≥ 0.3) or sleep quality (p = 1.0). The EIMD protocol produced significant strength loss, increased pain, reduced pressure-pain threshold, increased muscle thickness and elevated CK at 48 h. KO did not attenuate self-reported soreness, strength loss, increased muscle thickness, CK or LDH after EIMD compared with PLA. However, pressure-pain threshold was higher in the KO group than in PLA at 48 h (adjusted difference: 1.05 kg; 95% CI 0.08 to 2.02; p = 0.034), suggesting reduced pressure-pain sensitivity. For soreness evoked by standardised 5-kg pressure, in a post hoc sensitivity analysis excluding one influential PLA participant, the estimated difference was −10.18 mm (95% CI −19.83 to −0.53; p = 0.039) favoring KO. These data suggest that whilst achieving an O3I of 6.7% through KO, may reduce pressure evoked pain following EIMD, there is no meaningful effect on other markers of EIMD recovery.
Keywords
Krill oil; Omega-3 index; Body composition; Exercise-induced muscle damage
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