Vitamin D status and supplementation before and after bariatric surgery: a comprehensive literature review.

BACKGROUND: Bariatric surgery is the most effective long-term weight loss method. The most common procedures are Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG). Bariatric patients are at high risk of vitamin D deficiency (VDD) and insufficiency (VDI), which are associated with skeletal and nonskeletal ailments. There is no consensus regarding the optimal treatment for VDD/VDI in bariatric patients.

OBJECTIVES: To critically examine the literature on vitamin D status (serum 25[OH]D concentrations) pre- and postbariatric surgery as well as supplementation regimens currently used.

METHODS: We searched PubMed, Embase, and Cochrane from inception to May 2015 for articles relating to vitamin D, RYGB, and VSG. Of 208 citations retrieved, 30 were included.

RESULTS: Preoperative VDD (<20 ng/mL) ranged from 13% to 90%, while VDI (<30 ng/mL) was found in up to 98%. Prevalence remained similar postoperatively and was highest after RYGB. Most studies found dosages<800 IU daily insufficient postbariatric surgery. Other studies examined the effectiveness of dosages between 1000 and 5000 IU daily, reaching similar conclusions. Several studies suggested using 50,000 IU weekly plus a daily dose. No studies reported optimization.

CONCLUSIONS: It is widely accepted that serum 25(OH)D concentrations above 30 ng/mL are optimal; however, current postbariatric vitamin D supplementation fails to raise 25(OH)D above that level universally. This review highlights both the great need and the lack of consensus on the optimal supplementation regimen (dosage and frequency) for pre- and postbariatric patients. Future studies should investigate multiple regimens and attempt to identify methods for personalizing these regimens if found necessary.