Dietary Protein Intake and Overall Diet Quality in Adults with Cystic Fibrosis Following Elexacaftor/Tezacaftor/Ivacaftor Therapy

The RDA for dietary protein is likely to be insufficient for individuals with cystic fibrosis (CF), whereas a higher daily intake of ≥1.2g·kg‾¹·day‾¹ may be more appropriate in view of the increased risk of sarcopenia and reduced muscle quality. This study sought to characterise protein intake and diet quality in adults with cystic fibrosis (awCF), before and after elexacaftor/tezacaftor/ivacaftor (ETI) therapy, compared to healthy controls. Dietary intake was assessed by diet diary in awCF at baseline (BL, n=40) and at follow-up >3 months post ETI therapy (FUP, n=40), and in age-matched healthy controls (CON, n=80) free from known disease at a single time point. Protein intake dose and daily distribution, protein quality, protein source and overall diet quality was calculated for each participant. Both CON (1.39±0.47g·kg‾¹·day‾¹) and CF (BL: 1.44±0.52g·kg‾¹·day‾¹, FUP: 1.12±0.32g·kg‾¹·day‾¹) had a higher mean daily protein intake than the protein RDA of 0.75g·kg‾¹·day‾¹. There was a significant reduction in daily protein intake in the CF group at FUP (P=0.0003, d=0.73), with levels below the alternative suggested dietary intake of ≥1.2g·kg‾¹·day‾¹. There were no sex differences or noticeable effects on protein quality or source following the commencement of ETI therapy when compared to CON (all P>0.05), although overall diet quality decreased between time points (P=0.027, d=0.57). The observed reduction in daily protein intake in the present cohort emphasises the importance of ensuring appropriate dietary protein intake to promote healthy ageing in adults with CF. More research is needed to evidence base dietary protein requirements in this at-risk population.