Comparison of yogurt and ultra-high-temperature milk on serum osteocalcin and calcium levels in rats.

Dairy products may influence bone metabolism through calcium bioavailability and modulation of gut microbiota. This study compared the effects of yogurt and ultra-high-temperature (UHT) milk on serum osteocalcin and calcium levels in rats. Twenty-four male Wistar rats (Rattus norvegicus) were randomly assigned to control, UHT milk, and yogurt groups (n = 8 each) and administered the intervention for 8 weeks. Serum osteocalcin was measured at weeks 4 and 8, and serum calcium was measured at week 8. At week 4, both UHT milk and yogurt groups demonstrated significantly higher osteocalcin levels than the control group. A significant difference was also observed between the UHT milk and yogurt groups (P = 0.046). At week 8, osteocalcin levels remained significantly higher in both intervention groups than in the control group (P < 0.001), whereas no significant difference was detected between the UHT milk and yogurt groups (P = 0.674). Serum calcium levels were also significantly higher in the intervention groups than in the control group (P < 0.001), with higher levels observed in the yogurt group than in the UHT milk group (P = 0.037). Yogurt and UHT milk were associated with increased serum osteocalcin and calcium levels in rats. Yogurt was associated with earlier increases in circulating osteocalcin levels and higher serum calcium levels, whereas both dairy products demonstrated comparable osteocalcin levels after 8 weeks. These findings reflect changes in circulating biochemical markers associated with bone metabolism rather than direct evidence of enhanced bone formation or skeletal structural improvement.