{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,2]],"date-time":"2026-07-02T15:20:56Z","timestamp":1783005656692,"version":"3.54.5"},"reference-count":43,"publisher":"Oxford University Press (OUP)","issue":"1","license":[{"start":{"date-parts":[[2026,1,1]],"date-time":"2026-01-01T00:00:00Z","timestamp":1767225600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"funder":[{"DOI":"10.13039\/100014221","name":"Heritage Medical Research Institute","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100014221","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,1,31]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Isotopes of calcium (Ca) in blood and urine have been introduced as a potential clinical tool for monitoring bone mineral balance (BMB). While several works support the ability of Ca isotope composition (\u03b444\/42Ca) to capture a shift in BMB in response to external forcings (e.g. bed rest) or disease (e.g. osteoporosis), the influence of an individual\u2019s demographic, health status, diet or lifestyle on \u03b444\/42CaUrine\/Blood remains largely unconstrained. To gauge the effects of several variables among these four broader categories, we present a population study of \u03b444\/42CaUrine from 103 individuals (age 18-76). Age is negatively correlated with \u03b444\/42CaUrine, and we identify three other attributes (active vitamin D deficiency, vegetarian diet, and being post-menopausal) that lead to systematic differences in an individual\u2019s \u03b444\/42CaUrine. Fluctuations in Ca reabsorption generate significant intra-individual \u03b444\/42CaUrine variability. Within a typical range of reabsorption rates, however, the initial isotope composition (\u03b444\/42CaSerum) exerts the strongest control on inter-individual \u03b444\/42CaUrine variability. Using a simple Rayleigh model to express isotopic fractionation associated with Ca reabsorption in the kidneys, we find that a fractionation factor of 0.99972 reproduces the range of isotope ratios and excretion values for several, healthy individuals across three different studies and nearly a 30-year age span. Importantly, \u03b444\/42CaUrine variations in three post-menopausal women from three separate studies cannot be explained by the same model, pointing to a different mechanistic control of \u03b444\/42CaUrine in these subjects.<\/jats:p>","DOI":"10.1093\/mtomcs\/mfag017","type":"journal-article","created":{"date-parts":[[2026,6,3]],"date-time":"2026-06-03T11:51:31Z","timestamp":1780487491000},"source":"Crossref","is-referenced-by-count":0,"title":["Investigating apparent drivers of urinary Ca isotope variability in a sample population"],"prefix":"10.1093","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9937-8497","authenticated-orcid":false,"given":"Dan P","family":"Razionale","sequence":"first","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]},{"name":"Earth, Atmospheric and Planetary Sciences Department, Massachusetts Institute of Technology , Cambridge, MA 02139 ,","place":["United States"]},{"name":"Department of Earth, Environmental and Planetary Sciences, Brown University , Providence, RI 02912 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-3416-4687","authenticated-orcid":false,"given":"Kate","family":"Sanderson","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carlynda","family":"Lee","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rosa","family":"Grigoryan","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael A","family":"Kipp","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roxana T","family":"Shafiee","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4688-3024","authenticated-orcid":false,"given":"Emily","family":"Miaou","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hayward","family":"Melton","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Th\u00e9o","family":"Tacail","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6622-2907","authenticated-orcid":false,"given":"Fran\u00e7ois L H","family":"Tissot","sequence":"additional","affiliation":[{"name":"The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, CA 91125 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