Acute effects of dietary whey protein supplementation after endurance exercise on serum osteokine and inflammatory cytokine concentrations in endurance runners.

Endurance athletes have an increased risk of bone stress injuries due to high training and energy demands. Endurance training with inadequate recovery triggers a pro-inflammatory response, which can upregulate bone resorption for hours to days. Combined dietary protein and carbohydrate supplementation post-exercise has shown to attenuate bone resorption and pro-inflammatory cytokine responses, though the effect of dietary protein intake alone remains to be elucidated. This randomized cross-over, double-blinded study examined the acute effects of post-exercise protein supplementation on serum concentrations of osteokine and inflammatory cytokines in endurance runners. Fourteen young male and female (n = 7 each) endurance runners with a weekly training distance ≥40 km were included. Participants underwent (i) a protein treatment (0.5 g/kg whey isolate), and (ii) a control/water treatment; consumed immediately after a treadmill run to volitional exhaustion at 70% maximal oxygen consumption. Blood samples were taken at baseline, 0, 1, 2, 3, 4, and 24 h post-exercise, and analyzed with immunosorbent and multiplex assays. A linear mixed model assessed the effects of time and treatment for each marker, and interactions (sex, sequence, period, and baseline difference as covariates). There were no significant treatment by time effects for any blood markers. There were significant main effects of time for serum sclerostin (p < 0.0001), dickkopf-1 (p < 0.0001), osteoprotegerin (p < 0.0001), and tumor necrosis factor-alpha (p = 0.004); these markers increased immediately post-exercise and returned to baseline by 24 h. Acute whey protein supplementation did not induce a different bone or inflammatory response following exhaustive running exercise in young endurance runners compared to the control. Registration number: NCT06645119.