Background: Severe vitamin D deficiency is a common finding in morbid obesity, and the incidence increases markedly after RYGB. Normalization of vitamin D levels after RYGB is difficult to achieve because the degree of surgery-induced malabsorption is not known.
Objective: To develop a test that quantifies the changes in intestinal cholecalciferol absorption induced by Roux-en-Y gastric bypass (RYGB) surgery.
Methods: Absorption characteristics of cholecalciferol were studied in 14 morbidly obese, premenopausal women before and 4 weeks after laparoscopic RYGB. Serum cholecalciferol levels were measured at baseline and 1, 2, 3, and 14 days after a single oral dose of 50 000 IU solubilized cholecalciferol.
Results: Peak serum cholecalciferol levels were observed on day 1 in all patients. They were 26.6±3.7% lower after RYGB (P=0.02). Inter-individual variability was high.
Conclusion: Peak cholecalciferol levels are reduced by about 25% after RYGB. Further analysis suggested that the timing of sampling in the current study was not optimal. This might have caused an underestimation of the true decrease in cholecalciferol absorption induced by RYGB.