Vitamin D status of morbidly obese bariatric surgery patients.

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.