Background: Milk products are good sources of calcium and their consumption may reduce bone resorption and thus contribute to prevent bone loss.
Aim of the study: We tested the hypothesis that bedtime consumption of fermented milk supplemented with calcium inhibits the nocturnally enhanced bone resorption more markedly than fermented milk alone, and postulated that this effect was most pronounced when calcium absorption enhancers were added.
Methods: In a controlled, parallel, double-blind intervention study over 2 weeks we investigated the short-term effects of two fermented milks supplemented with calcium from milk minerals (f-milk + Ca, n = 28) or calcium from milk minerals, inulin-type fructans and caseinphosphopeptides (f-milk + Ca + ITF + CPP; n = 29) on calcium and bone metabolism in healthy, postmenopausal women, and compared them with the effect of a fermented control milk without supplements (f-milk, n = 28). At bedtime 175 ml/d of either test milk was consumed. Fasting blood samples and 48 h-urine were collected at baseline and at the end of the intervention. Urine was divided into a pooled daytime and nighttime fraction. Multifactorial ANOVA was performed.
Results: Fermented milk independent of a supplement (n = 85) reduced the nocturnal excretion of deoxypyridinoline, a marker of bone resorption, from 11.73 +/- 0.54 before to 9.57 +/- 0.54 micromol/mol creatinine at the end of the intervention (P = 0.005). No effect was seen in the daytime fraction. Differences between the three milks (n = 28 resp. 29) were not significant. Fermented milk reduced bone alkaline phosphatase, a marker of bone formation, from 25.03 +/- 2.08 to 18.96 +/- 2.08 U/l, with no difference between these groups either. Fermented milk increased the nocturnal but not daytime urinary excretion of calcium and phosphorus. The effects on calcium and phosphorus excretion were mainly due to the group supplemented with Ca + ITF + CPP.
Conclusion: Bedtime consumption of fermented milk reduced the nocturnal bone resorption by decelerating its turnover. Supplemented calcium from milk mineral had no additional effect unless the absorption enhancers ITF + CPP were added. A stimulated intestinal calcium absorption may be assumed, since urinary calcium excretion increased at a constant bone resorption.