title: Intestinal Calcium Absorption Decreases Dramatically After Gastric Bypass Surgery Despite Optimization of Vitamin D Status.
abstract: 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)2 D-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 ≥30 ng/mL) and Ca intake (1200 mg daily) in a prospective cohort of 33 obese adults (BMI 44.7 ± 7.4 kg/m(2)). 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 ± 8.4 kg (25.8% ± 5.2% of preoperative weight). FCA decreased from 32.7% ± 14.0% preoperatively to 6.9% ± 3.8% postoperatively (p < 0.0001), 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)2 D increased (p ≤ 0.02). Bone turnover markers increased markedly, areal BMD decreased at the proximal femur, and volumetric BMD decreased at the spine (p < 0.001). Those with lower postoperative FCA had greater increases in serum CTx (ρ = -0.43, p = 0.01). Declines in FCA and BMD were not correlated over the 6 months. In conclusion, FCA decreased dramatically after RYGB, even with most 25OHD levels ≥30 ng/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.
authors: Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.|Department of Medicine, University of California, San Francisco, CA, USA.
authors: Anne L
authors: AL
authors: Schafer
authors: Department of Nutrition Science, Purdue University, West Lafayette, IN, USA.
authors: Connie M
authors: CM
authors: Weaver
authors: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors: Dennis M
authors: DM
authors: Black
authors: Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.|Department of Medicine, University of California, San Francisco, CA, USA.
authors: Amber L
authors: AL
authors: Wheeler
authors: Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.|Department of Medicine, University of California, San Francisco, CA, USA.
authors: Hanling
authors: H
authors: Chang
authors: Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
authors: Gina V
authors: GV
authors: Szefc
authors: Department of Surgery, University of California, San Francisco, CA, USA.|Surgical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
authors: Lygia
authors: L
authors: Stewart
authors: Department of Surgery, University of California, San Francisco, CA, USA.
authors: Stanley J
authors: SJ
authors: Rogers
authors: Department of Surgery, University of California, San Francisco, CA, USA.
authors: Jonathan T
authors: JT
authors: Carter
authors: Department of Surgery, University of California, San Francisco, CA, USA.
authors: Andrew M
authors: AM
authors: Posselt
authors: Medical Service, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.|Department of Medicine, University of California, San Francisco, CA, USA.
authors: Dolores M
authors: DM
authors: Shoback
authors: Department of Medicine, The Johns Hopkins University, Baltimore, MD, USA.
authors: Deborah E
authors: DE
authors: Sellmeyer
mesh_terms: D000328:Adult; D000368:Aged; D016723:Bone Remodeling; D002118:Calcium / Q000378:metabolism*; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium
keywords: BARIATRIC SURGERY; BIOCHEMICAL MARKERS OF BONE TURNOVER; CALCIUM ABSORPTION; GASTRIC BYPASS SURGERY; NUTRITION; VITAMIN D
references: J Bone Miner Res. 1990 Nov;5(11):1135-8
references: 2270776
references: Ann Surg. 2013 Jan;257(1):87-94
references: 23235396
references: Am J Clin Nutr. 1995 Oct;62(4):730-4
references: 7572700
references: Am J Clin Nutr. 2013 Mar;97(3):637-45
references: 23364004
references: J Clin Endocrinol Metab. 2008 Oct;93(10):3735-40
references: 18647809
references: Obes Surg. 2014 Oct;24(10):1595-602
references: 24744188
references: Lancet Diabetes Endocrinol. 2014 Feb;2(2):165-74
references: 24622720
references: J Lab Clin Med. 1965 Nov;66(5):822-9
references: 5844609
references: J Bone Miner Res. 1989 Aug;4(4):469-75
references: 2816496
references: Osteoporos Int. 2014 Jan;25(1):151-8
references: 23912559
references: Obes Surg. 2014 May;24(5):796-805
references: 24374942
references: Ann Intern Med. 1991 Dec 15;115(12):956-61
references: 1952493
references: JAMA. 2004 Oct 13;292(14):1724-37
references: 15479938
references: Obes Surg. 2009 Jul;19(7):860-6
references: 19412643
references: Clin Chim Acta. 1985 Feb 28;146(1):97-101
references: 3987043
references: Calcif Tissue Int. 1989 May;44(5):308-11
references: 2496901
references: Obes Surg. 2009 Jan;19(1):41-6
references: 18683014
references: J Bone Miner Res. 2014 Mar;29(3):542-50
references: 23929784
references: Phys Med Biol. 2014 Dec 21;59(24):7819-34
references: 25419618
references: J Bone Miner Res. 2014 Jul;29(7):1507-18
references: 24677277
references: Obes Surg. 2008 Feb;18(2):145-50
references: 18175194
references: Obesity (Silver Spring). 2006 Nov;14(11):1940-8
references: 17135609
references: J Bone Miner Res. 2012 Jan;27(1):119-24
references: 21915902
references: Ann Intern Med. 2000 Mar 7;132(5):345-53
references: 10691584
references: Am J Clin Nutr. 2000 Sep;72(3):690-3
references: 10966885
references: Nat Rev Endocrinol. 2012 Sep;8(9):544-56
references: 22525731
references: Am J Clin Nutr. 1986 Feb;43(2):299-305
references: 3946294
references: Osteoporos Int. 2009 Sep;20(9):1539-45
references: 19107384
references: Am J Clin Nutr. 2000 Aug;72(2):466-71
references: 10919942
references: N Engl J Med. 2007 Aug 23;357(8):741-52
references: 17715408
references: Obes Surg. 2008 Jan;18(1):58-65
references: 18074189
references: J Comput Assist Tomogr. 1999 Jan-Feb;23(1):130-7
references: 10050823
references: Obesity (Silver Spring). 2013 Mar;21 Suppl 1:S1-27
references: 23529939
references: Osteoporos Int. 2012 Nov;23(11):2607-14
references: 22282301
references: J Am Diet Assoc. 2009 Jul;109(7):1237-40
references: 19559142
references: Ann Surg. 2006 May;243(5):701-4; discussion 704-5
references: 16633006
references: J Nutr. 1994 May;124(5):674-82
references: 8169659
references: Am J Clin Nutr. 2004 Jul;80(1):123-30
references: 15213038
references: Endocr Pract. 2009 Sep-Oct;15(6):528-33
references: 19491072
references: J Clin Epidemiol. 1990;43(12):1327-35
references: 2254769