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J Surg Res. 2010 Dec;164(2):198-202. doi: 10.1016/j.jss.2010.06.029. Epub 2010 Sep 8.

Vitamin D status of morbidly obese bariatric surgery patients.

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Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792, USA.



Abnormal vitamin D levels are common in bariatric surgery patients. The incidence of deficiencies and the response to therapy is not accurately delineated. The purpose of this study was to define the vitamin D status of patients who undergo either a malabsorptive (gastric bypass) or restrictive (adjustable gastric band) bariatric surgery both prior to and after surgery.


A retrospective analysis was performed on patients to undergo bariatric surgery from July 2002 to February 2007. Serum levels of vitamin D (Vit D), parathyroid hormone (PTH), and calcium were analyzed.


Mean patient age was 45 y; 82% of patients were women. Of 127 total patients, 84% were Vit D deficient preoperatively. These patients had a higher preoperative body mass index (BMI) than those with normal Vit D levels on initial assessment (BMI 44 versus 50 kg/m(2), P < 0.01). A correlation was found between preoperative BMI and Vit D (r(2) = 0.12, P < 0.01) and PTH levels (r(2) = 0.07, P < 0.01). One year following gastric bypass surgery, 20% of patients with elevated PTH levels had normal Vit D levels. The incidence of observed deficiencies for adjustable gastric band versus gastric bypass did not differ statistically at any interval.


Morbidly obese patients seeking bariatric surgery are often deficient in Vit D, a fact that should be accounted for when evaluating the impact of bariatric surgery on Vit D levels. Elevated BMI and increasing degrees of obesity may be risk factors for both Vit D deficiency and secondary hyperparathyroidism. Despite normal Vit D levels, some gastric bypass patients continue to show elevated levels of PTH.

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