Few interventions directly compare equivalent calcium and vitamin D from dairy vs supplements on the same bone outcomes.
Objectives and Methods: Using 41Ca tracer techniques, determine if 4 servings/d of dairy foods reduces Ca excretion more than an equivalent amount of Ca and vitamin D from supplements. Secondary objective was to evaluate the time course for change in Ca excretion.
Design: In this crossover trial, postmenopausal women (n=12) were dosed orally with 100nCi of 41Ca and received dairy (4 servings/d dairy foods; ~1300 mg Ca, 400 IU vitamin D3/d) or supplements (1200 mg Ca carbonate/d, 400 IU vitamin D3/d) in random order. Treatments lasted 6 weeks separated by a 6 week washout (WO). Ca was extracted from weekly 24 h urine collections; accelerator mass spectrometry (AMS) was used to determine the urinary 41/40Ca ratio.
Results: Urinary 41/40Ca ratio decreased significantly with treatment, but there was no difference between treatments. The reduction in 41Ca excretion was observed in 12 weeks (P=0.0007 and P<0.001 for dairy and supplements, respectively). Return to pre-treatment excretion levels was observed within 12 weeks WO (P=0.0024).
Conclusion: These data suggest that changes in urinary Ca excretion with increases or decreases in Ca intake occur within 12 weeks; most likely via the miscible pool to maintain Ca homeostasis.
14 May 2016 - 17 May 2016