High-Dose Vitamin D Supplementation is Necessary After Bariatric Surgery: A Prospective 2-Year Follow-up Study.

Background: We assessed the need of vitamin D supplementation to achieve normal 25-hydroxyvitamin D (25[OH]D) levels after bariatric surgery and whether there were differences between laparoscopy sleeve gastrectomy (LSG) and laparoscopic Roux-en-Y gastric bypass (LRYGB).
Methods: A total of 164 morbid obese patients undergoing bariatric surgery from January 2008 to June 2011 were followed for 2 years. Serum levels of 25(OH)D and intact parathyroid hormone (iPTH) were measured preoperatively and at 3, 6, 9, 12, 18, and 24 months after operation. All patients received 400 IU/day of 25(OH)D. Patients received additional supplementation with 16,000 IU of vitamin D3 (calcifediol) every 2 weeks if 25(OH)D serum levels were < 30 ng/mL (intervention group).
Results: Ninety-six (58.5 %) patients underwent LSG and 68 (41.5 %) LRYGB. A total of 106 (64.6 %) patients received calcifediol supplementation (62 in the LSG group and 44 in the LRYGB group). Normal 25(OH)D levels at 24 months were recorded in 69 % of patients in the intervention group and in 48.3 % in the non-intervention group. At 24 months, mean 25(OH)D levels in the non-intervention group were significantly lower among LRYGB patients than among LSG patients (P = 0.009). In the intervention group, normal 25(OH)D levels were achieved in 60 % of patients treated with LSG and in 22.2 % of those treated with LRYGB. Secondary hyperparathyroidism was presented in 49 (29.9 %) patients preoperatively but without significant differences in iPTH levels between the two surgical procedures.
Conclusion: Patients undergoing bariatric surgery should receive high-dose vitamin D supplementation independently of the surgical technique.