Magnitude and timescales of Ca isotope variability in human urine: implications for bone mass balance monitoring.

Calcium (Ca) isotopes in blood/urine are emerging biomarkers of bone mineral balance (BMB) in the human body. While multiple studies have investigated Ca isotopes in patients suffering from diseases affecting BMB, comparatively little effort has been devoted to understanding the homeostasis of Ca isotopes in healthy individuals. Here, we report on a longitudinal study of the urine Ca isotope composition (δ44/42CaUrine) from 22 healthy participants (age 19-60) over timescales ranging from days to months.