Propionibacterium cheese and bone turnover in active young adults: a randomized-controlled trial

Introduction: Young physically active individuals exposed to prolonged physiological stress and low energy availability are prone to reduced gonadal steroid protection and increased bone turnover. Nutritional strategies that favor positive bone remodeling balance are of clinical interest. Jarlsberg cheese contains Propionibacterium freudenreichii (PF), which produces vitamin K₂ and 1,4-dihydroxy-2-naphthoic acid (DHNA), compounds with potential favorable effects on bone health. Materials and Methods: In this 24-week sex-stratified randomized-controlled trial, 60 young physically active adults engaged in endurance training were allocated to daily intake of either Jarlsberg cheese or a nutritionally comparable control cheese without PF. The primary outcome was change in serum total osteocalcin (tOC). Secondary outcomes were changes in carboxylated osteocalcin (cOC), procollagen type 1 N-terminal propeptide (P1NP), cross-linked C-terminal telopeptide of type I collagen (CTX), P1NP/CTX ratio, lumbar spine bone mineral density (BMD), and trabecular bone score (TBS). Results: After 24 weeks, serum tOC was significantly higher in the Jarlsberg group than in controls (38.0 vs. 26.8 ng/mL, p < 0.01). cOC and P1NP/CTX ratio increased in favor of the Jarlsberg group (p = 0.03). Lumbar spine BMD increased in the Jarlsberg group (mean change 0.012 g/cm2, p = 0.03), with a greater increase than in controls (p = 0.05), and TBS showed a positive trend in the Jarlsberg group. Conclusion: Daily intake of cheese-containing PF was associated with favorable changes in bone turnover markers and increase in lumbar spine BMD. These findings suggest that PF-fermented cheese may support bone metabolism in young individuals exposed to reduced hormonal protection and high bone turnover. Protocol number: XCS-Jarlsberg/IIA. ClinicalTrials.gov: NCT 06688032.