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

Post-exercise whey protein supplementation produced no significant treatment by time effects for any blood markers compared to water control.

• Randomized cross-over, double-blinded study design with 14 young male and female endurance runners (n=7 each sex)
• Protein treatment consisted of 0.5 g/kg whey isolate consumed immediately after exercise
• Control treatment was water consumed immediately after exercise
• Linear mixed model assessed effects of time and treatment with sex, sequence, period, and baseline difference as covariates
• No significant treatment by time interactions were found for any measured blood markers

Serum sclerostin showed a significant main effect of time, increasing immediately post-exercise and returning to baseline by 24 hours.

• Significant main effect of time for sclerostin (p < 0.0001)
• Blood samples were taken at baseline, 0, 1, 2, 3, 4, and 24 h post-exercise
• The response was independent of treatment (protein vs. water)
• Sclerostin is an osteokine involved in inhibition of bone formation

Serum dickkopf-1 (DKK-1) showed a significant main effect of time, increasing immediately post-exercise and returning to baseline by 24 hours.

• Significant main effect of time for DKK-1 (p < 0.0001)
• Response was independent of treatment condition
• DKK-1 is an osteokine that inhibits the Wnt signaling pathway involved in bone formation
• Samples analyzed with immunosorbent and multiplex assays

Serum osteoprotegerin showed a significant main effect of time, increasing immediately post-exercise and returning to baseline by 24 hours.

• Significant main effect of time for osteoprotegerin (p < 0.0001)
• Response was independent of treatment condition
• Osteoprotegerin is an osteokine that acts as a decoy receptor inhibiting osteoclast differentiation and bone resorption

Serum tumor necrosis factor-alpha (TNF-α) showed a significant main effect of time, increasing immediately post-exercise and returning to baseline by 24 hours.

• Significant main effect of time for TNF-α (p = 0.004)
• Response was independent of treatment condition
• TNF-α is a pro-inflammatory cytokine that can upregulate bone resorption
• Increase and recovery pattern mirrored that of the measured osteokines

The study population consisted of young male and female endurance runners with high weekly training volumes who performed exhaustive treadmill running.

• 14 participants total (n=7 male, n=7 female)
• Participants had a weekly training distance ≥40 km
• Exercise protocol was a treadmill run to volitional exhaustion at 70% maximal oxygen consumption
• Each participant underwent both treatments in a cross-over design

Endurance athletes face increased risk of bone stress injuries due to high training and energy demands, with inadequate recovery triggering a pro-inflammatory response that can upregulate bone resorption for hours to days.

• Combined dietary protein and carbohydrate supplementation post-exercise has been shown to attenuate bone resorption and pro-inflammatory cytokine responses
• The effect of dietary protein intake alone on bone and inflammatory markers remained to be elucidated prior to this study
• The pro-inflammatory response to endurance training can persist for hours to days