{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,10]],"date-time":"2026-10-10T02:48:01Z","timestamp":1791600481483,"version":"4.3.4"},"reference-count":45,"publisher":"Oxford University Press (OUP)","issue":"8","license":[{"start":{"date-parts":[[2015,1,31]],"date-time":"2015-01-31T00:00:00Z","timestamp":1422662400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/journals\/pages\/open_access\/funder_policies\/chorus\/standard_publication_model"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2015,8,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title>\u2003<\/jats:title>\n                    <jats:p>Roux-en-Y gastric bypass (RYGB) surgery has negative effects on bone, mediated in part by effects on nutrient absorption. Not only can RYGB result in vitamin D malabsorption, but the bypassed duodenum and proximal jejunum are also the predominant sites of active, transcellular, 1,25(OH)2D-mediated calcium (Ca) uptake. However, Ca absorption occurs throughout the intestine, and those who undergo RYGB might maintain sufficient Ca absorption, particularly if vitamin D status and Ca intake are robust. We determined the effects of RYGB on intestinal fractional Ca absorption (FCA) while maintaining ample 25OHD levels (goal \u226530\u2009ng\/mL) and Ca intake (1200\u2009mg daily) in a prospective cohort of 33 obese adults (BMI 44.7\u2009\u00b1\u20097.4\u2009kg\/m2). FCA was measured preoperatively and 6 months postoperatively with a dual stable isotope method. Other measures included calciotropic hormones, bone turnover markers, and BMD by DXA and QCT. Mean 6-month weight loss was 32.5\u2009\u00b1\u20098.4\u2009kg (25.8%\u2009\u00b1\u20095.2% of preoperative weight). FCA decreased from 32.7%\u2009\u00b1\u200914.0% preoperatively to 6.9%\u2009\u00b1\u20093.8% postoperatively (p\u2009&amp;lt;\u20090.0001), despite median (interquartile range) 25OHD levels of 41.0 (33.1 to 48.5) and 36.5 (28.8 to 40.4) ng\/mL, respectively. Consistent with the FCA decline, 24-hour urinary Ca decreased, PTH increased, and 1,25(OH)2D increased (p\u2009\u2264\u20090.02). Bone turnover markers increased markedly, areal BMD decreased at the proximal femur, and volumetric BMD decreased at the spine (p\u2009&amp;lt;\u20090.001). Those with lower postoperative FCA had greater increases in serum CTx (\u03c1\u2009=\u2009\u22120.43, p\u2009=\u20090.01). Declines in FCA and BMD were not correlated over the 6 months. In conclusion, FCA decreased dramatically after RYGB, even with most 25OHD levels \u226530\u2009ng\/mL and with recommended Ca intake. RYGB patients may need high Ca intake to prevent perturbations in Ca homeostasis, although the approach to Ca supplementation needs further study. Decline in FCA could contribute to the decline in BMD after RYGB, and strategies to avoid long-term skeletal consequences should be investigated. \u00a9 2015 American Society for Bone and Mineral Research.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/jbmr.2467","type":"journal-article","created":{"date-parts":[[2015,1,31]],"date-time":"2015-01-31T05:59:02Z","timestamp":1422683942000},"page":"1377-1385","source":"Crossref","is-referenced-by-count":151,"title":["Intestinal Calcium Absorption Decreases Dramatically After Gastric Bypass Surgery Despite Optimization of Vitamin D Status"],"prefix":"10.1093","volume":"30","author":[{"given":"Anne L","family":"Schafer","sequence":"first","affiliation":[{"name":"Department of MedicineUniversity of CaliforniaSan FranciscoCAUSA"},{"name":"Medical ServiceSan Francisco Veterans Affairs Medical CenterSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Connie M","family":"Weaver","sequence":"additional","affiliation":[{"name":"Department of Nutrition SciencePurdue UniversityWest LafayetteINUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dennis M","family":"Black","sequence":"additional","affiliation":[{"name":"Department of Epidemiology and BiostatisticsUniversity of CaliforniaSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amber L","family":"Wheeler","sequence":"additional","affiliation":[{"name":"Department of MedicineUniversity of CaliforniaSan FranciscoCAUSA"},{"name":"Medical ServiceSan Francisco Veterans Affairs Medical CenterSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hanling","family":"Chang","sequence":"additional","affiliation":[{"name":"Department of MedicineUniversity of CaliforniaSan FranciscoCAUSA"},{"name":"Medical ServiceSan Francisco Veterans Affairs Medical CenterSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gina V","family":"Szefc","sequence":"additional","affiliation":[{"name":"Medical ServiceSan Francisco Veterans Affairs Medical CenterSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lygia","family":"Stewart","sequence":"additional","affiliation":[{"name":"Surgical ServiceSan Francisco Veterans Affairs Medical CenterSan FranciscoCAUSA"},{"name":"Department of SurgeryUniversity of CaliforniaSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stanley J","family":"Rogers","sequence":"additional","affiliation":[{"name":"Department of SurgeryUniversity of CaliforniaSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan T","family":"Carter","sequence":"additional","affiliation":[{"name":"Department of SurgeryUniversity of CaliforniaSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew M","family":"Posselt","sequence":"additional","affiliation":[{"name":"Department of SurgeryUniversity of CaliforniaSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dolores M","family":"Shoback","sequence":"additional","affiliation":[{"name":"Department of MedicineUniversity of CaliforniaSan FranciscoCAUSA"},{"name":"Medical ServiceSan Francisco Veterans Affairs Medical CenterSan FranciscoCAUSA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Deborah E","family":"Sellmeyer","sequence":"additional","affiliation":[{"name":"Department of MedicineThe Johns Hopkins 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