A subgroup analysis revealed no benefits of whey protein supplementation in individuals with sarcopenia and pre-frailty on serum CRP (k = 3, MD: 0·02, 95 % CI: –1·60, 1·65, I2 = 75 %) (online Supplementary Fig. 13a) and TNF-α levels (k = 2, MD: –0·13 95 % CI: -0·99, 0·73, I2 = 45 %) (online Supplementary Fig. 13b); however, whey protein displayed a significant reduction of serum IL-6 levels (k = 3, MD: –0·98, 95 % CI: –1·56, –0·39, I2 = 0 %) (Supplementary Fig. 13c). This evidence concerns the gene IL6 and sarcopenia.