1. Despite proactive vitamin D supplementation, 80% of morbidly obese patients who underwent omega-loop gastric bypass were vitamin D deficient at 1 year post-op.
2. BMI >45 was a strong predictor of post-operative vitamin D deficiency
Evidence Rating Level: 2 (Good)
Study Rundown: Omega-loop gastric bypass (OLGB) is an increasingly employed technique involving a bypass of the stomach and proximal small intestine to achieve weight reduction in morbidly obese individuals. The procedure employs a single anastomosis compared to the 2 anastomoses required for the conventionally performed Roux-en-Y gastric bypass (RYGB). However, forgoing absorption of any length of small intestine, which occurs in both OGLB and RYGB, results in malabsorption of essential vitamins and nutrients, the extent of which is determined by how distally the connection is made on the duodenum. Given the lack of studies examining the effects of OLGB on nutritional deficits, this study attempted to characterize the profiles of vitamin D, parathyroid hormone, and other bone metabolism markers in patients undergoing the procedure. Despite proactive vitamin D supplementation, the authors found only a marginal reduction in rates of vitamin D deficiencies (96% to 80%) and hyperparathyroidism secondary to calcium malabsorption (17% to 14%) at 1-year postoperatively in individuals undergoing OLBG. Markers of bone resorption were also significantly elevated. The study reveals the high incidence of vitamin D deficiency in patients following OLBG, which can predispose them to metabolic bone disease among a host of other negative outcomes. The lack of efficacy in supplementation calls for additional means to combat such nutritional defects. Limitations include the retrospective nature of the study, a relatively significant number of patients lost to follow-up, and small sample size.
Relevant Reading: Vitamin D Status of Morbidly Obese Bariatric Surgery Patients
In-Depth [retrospective]: A total of 86 morbidly obese patients underwent OLGB between February 2011 and 2013 at the General Hospital of Vienna. Thirty-six were excluded due to insufficient data. All surgeries were performed laparoscopically with the same surgical team. Data was collected pre-operatively and at 3 months in all 50 patients, 6 months in 49 patients, and 12 months in 35 patients. A vitamin D level less than 75 nmol/L was the threshold to be considered deficient. Pre-operatively, 96% of patients presented with vitamin D deficiency. The incidence decreased to 80% at 1 year post-op. Seventeen percent of patients had secondary hyperparathyroidism pre-operatively which increased to 30% at 3 months follow-up and subsequently declined to 14.3% at 1 year. BMI > 45 kg/m was a strong predictor of vitamin D deficiency (OR 3.10, 95% CI 1.01-9.51) post-operatively. An increase in mean BMI was correlated with an increase in presence of secondary hyperparathyroidism. Twenty percent of patients had elevated levels of C-telopeptide, a marker of bone turnover, compared to 97% at 1-year follow-up.
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