Greek Yogurt Compared with Whey Protein Supplementation in Adolescent Athletes Throughout a Competitive Season

Protein intake during adolescence may influence bone development and immune status, yet the comparative effects of wholefood protein sources compared with protein isolates in adolescent athletes remain unclear.

To compare the effects of Greek yogurt (GY) and whey protein (WP) supplementation on bone and inflammation markers in adolescent athletes throughout a competitive season.

Athletes completed an initial control period on their habitual diets (weeks 0‒8), followed by randomization to GY (n = 24; 15.8 ± 1.1 y; 11 females) or WP (n = 23; 16.0 ± 1.4 y; 10 females) for a 16-wk intervention (weeks 8‒24). GY consumed 2 servings per day of 175 g GY (17 g protein); WP received an isonitrogenous WP supplement. Blood samples and body composition assessments were obtained at weeks 0, 8, 16, and 24.

Procollagen type I N-terminal propeptide, insulin-like growth factor-1, and receptor activator of nuclear factor κB ligand remained stable. Osteocalcin and osteoprotegerin showed sex-specific between-group differences: osteocalcin declined throughout weeks 0‒24 in GY males, whereas osteoprotegerin declined during weeks 0‒16 in GY females and was elevated at the end of the control period in WP females. C-terminal telopeptide of type I collagen and sclerostin showed intervention group-dependent, but not sex-dependent, differences. C-terminal telopeptide of type I collagen increased transiently from week 8 to week 16 and returned to baseline by week 24 only in GY. Sclerostin concentrations fluctuated, and at 24 wk, were not different from baseline in GY but were higher than baseline in WP. At week 16, interleukin (IL)-1β increased in WP, and IL-6 decreased in GY. IL-10 and tumor necrosis factor α increased during the control period and decreased with WP only in females.

Increased protein intake, independent of source, was associated with modest, often sex-specific fluctuations in bone and inflammatory markers in adolescent athletes, potentially influenced by growth and training-related factors across the competitive season. This trial was registered at clinicaltrials.gov as NCT05922462.