The efficacy of three different vitamin D supplementation protocols after the Roux-en-Y gastric bypass procedure

The purpose of this research was to assess the efficacy of three vitamin D supplementation protocols after Roux-en-Y gastric bypass surgery. The efficacy of supplementation was defined in terms of the nmol/L rise in serum 25-hydroxyvitamin D [25(OH)D] per one mcg oral supplementation and number of subjects achieving optimal serum 25(OH)D (≥80 nmol/L) at twelve-months postoperative. Between November 2006 and December 2007, 47 subjects undergoing bariatric surgery, aged 21 to 62 years, enrolled in the study. Subjects with preoperative serum 25(OH)D levels ≥50 nmol/L received 1200 IU vitamin D3 daily. Deficient subjects (serum 25(OH)D levels <50 nmol/L) were randomized to receive 50,000 IU vitamin D2 weekly or 2800 IU vitamin D3 daily postoperatively. In addition, 1200 IU D3/day were provided from a multivitamin/mineral and calcium supplementation. The primary outcome measure was the change in serum 25(OH)D from preoperative to twelve-months postoperative. The mean preoperative 25(OH)D level for the non-deficient subjects (n=30) was 71.0 +/- 15.6 nmol/L. The mean preoperative 25(OH)D level for the deficient subjects (n=17), was 40.1 +/- 15.6 nmol/L. At twelve-months postoperatively, 72% of subjects taking 50,000 IU D2 weekly attained optimal vitamin D status. Fifty percent of subjects taking 2800 IU D3 daily and 50% of the subjects taking 1200 IU D3 daily achieved optimal vitamin D levels. The change in serum 25(OH)D from preoperative to twelve-months postoperative per mcg supplementation for all groups was as follows: 1200 IU D3/day: 0.61 +/- 1.6 nmol/L; 2800 IU D3/day (+ 1200 IU D3/day): 0.42 +/- 0.27 nmol/L; 50,000 IU D 2/week (+ 1200 IU D3/day): 0.32 +/- 0.23 nmol/L. The efficacy of weekly vitamin D2 supplementation versus daily vitamin D3 supplementation (nmol/L increase in 25(OH)D per mcg supplemented) was not different. Both types of vitamin D can be used for vitamin D supplementation. All three supplementation protocols were less effective at raising 25(OH)D levels than expected. During vitamin D repletion after Roux-en-Y gastric bypass surgery, serum 25(OH)D levels should be monitored and vitamin D doses adjusted.