This study examined whether the effects of krill oil supplementation on muscle function and size differ by sex, age or BMI in healthy older adults. This was a secondary exploratory analysis of a previous randomised controlled trial. Men and women aged ≥65 years, with BMI < 35 kg/m² and engaging in <1 h per week of structured exercise, were enrolled in a randomised, double-blind, controlled trial (NCT04048096) between March 2018 and March 2020. Participants received either 4 g/day krill oil or a control oil for 6 months. Ninety-four participants were included (Control n = 45; 27 women, 18 men; Krill n = 49; 26 women, 23 men) with muscle size, strength and neuromuscular function measured before and after the intervention period. Responses to intervention were compared between subgroups by sex (male/female), age (≤70 years/> 70 years) and BMI (≤24.9 kg/m ² / > 25 kg/m ² ). Increases in muscle strength, size, and physical function in response to krill oil supplementation were comparable across age, sex and BMI subgroups (all P > 0.05). This was similar for neuromuscular measures although increases in the Mwave the response to krill oil supplementation differed by sex, with no change over time in females in either krill or control groups, but an increase in Mwave in males in the krill group (+3.80 [1.72–5.88] mV, p = 0.016) with a tendency for a decrease in the control group (−3.71 [1.58–6.05] mV, p = 0.059). In conclusion, krill oil supplementation improved muscle strength and size in older adults regardless of age, sex and BMI status, although neuromuscular effects of krill oil on membrane excitability, via the Mwave, may be more pronounced in men.

ClinicalTrials.gov Identifier: NCT04048096