Guidelines on vitamin D replacement in bariatric surgery: Identification and systematic appraisal.

INTRODUCTION: Bariatric surgery is the most effective therapeutic option to reduce weight in morbidly obese individuals, but it results in a number of mineral and vitamin deficiencies. Clinical Practice Guidelines (CPGs) attempt to balance those benefits and harms to provide guidance to physicians and patients. OBJECTIVES: We compare and evaluate the quality of the evidence and of the development process of current CPGs that provide recommendations on vitamin D replacement in patients undergoing bariatric surgery, using a validated tool. METHODS: We searched 4 databases, with no time restriction, to identify relevant and current CPGs. Two reviewers assessed eligibility and abstracted data, in duplicate. They evaluated the quality of CPGs development process using the Appraisal of Guidelines, Research, and Evaluation II (AGREE II) tool that consists of 6 domains. A content expert verified those assessments. RESULTS: We identified 3 eligible CPGs: (1) the Endocrine Society (ES) guidelines (2010); (2) the American Association of Clinical Endocrinologists (AACE), The Obesity Society (TOS), and the American Society for Metabolic & Bariatric Surgery (ASMBS) guidelines (update 2013); and (3) the Interdisciplinary European (IE) guidelines on Metabolic and Bariatric Surgery (latest update 2014). The ES and the AACE/TOS/ASMBS guidelines recommended high doses of vitamin D, varying from 3000IU daily to 50,000IU 1-3 times weekly. Vitamin D doses were not mentioned in the IE guidelines. The recommendations were based on a low quality of evidence, if any, or limited to a single high quality trial, for some outcomes. In terms of quality, only the IE guidelines described their search methodology but none of the CPGs provided details on evidence selection and appraisal. None of the three CPGs rigorously assessed the preferences of the target population, resource implications, and the applicability of these guidelines. According to the AGREE II tool, we rated the ES guidelines as average in quality, and the other two as low in quality. CONCLUSION: Current CPGs recommendations on vitamin D supplementation in bariatric surgery differ between societies. They do not fulfill criteria for optimal guideline development, in part possibly due to limited resources, and are based on expert opinion. Thus, the pressing need for high quality randomized trials to inform CPGs, to be developed based on recommended standards.

Hypovitaminosis D in bariatric surgery: A systematic review of observational studies.

BACKGROUND: Obesity is a public health problem that carries global and substantial social and economic burden. Relative to non-surgical interventions, bariatric surgery has the most substantial and lasting impact on weight loss. However, it leads to a number of nutritional deficiencies requiring long term supplementation. OBJECTIVES: The aims of this paper are to review 25-hydroxyvitamin D [25(OH)D] status pre and post bariatric surgery, describe the dose response of vitamin D supplementation, and assess the effect of the surgical procedure on 25(OH)D level following supplementation. METHODS: We searched Medline, PubMed, the Cochrane Library and EMBASE, for relevant observational studies published in English, from 2000 to April 2015. The identified references were reviewed, in duplicate and independently, by two reviewers. RESULTS: We identified 51 eligible observational studies assessing 25(OH)D status pre and/or post bariatric surgery. Mean pre-surgery 25(OH)D level was below 30ng/ml in 29 studies, and 17 of these studies showed mean 25(OH)D levels ≤20ng/ml. Mean 25(OH)D levels remained below 30ng/ml following bariatric surgery, despite various vitamin D replacement regimens, with only few exceptions. The increase in post-operative 25(OH)D levels tended to parallel increments in vitamin D supplementation dose but varied widely across studies. An increase in 25(OH)D level by 9-13ng/ml was achieved when vitamin D deficiency was corrected using vitamin D replacement doses of 1100-7100IU/day, in addition to the usual maintenance equivalent daily dose of 400-2000IU (total equivalent daily dose 1500-9100IU). There was no difference in mean 25(OH)D level following supplementation between malabsorptive/combination procedures and restrictive procedures. CONCLUSION: Hypovitaminosisis D persists in obese patients undergoing bariatric surgery, despite various vitamin D supplementation regimens. Further research is needed to determine the optimal vitamin D dose to reach desirable 25(OH)D levels in this population, and to demonstrate whether this dose varies according to the surgical procedure.