Low concentrations of vitamin B-6, vitamin C, 25-hydroxyvitamin D, and vitamin E adjusted for lipids are prevalent in morbidly obese Norwegian patients seeking weight-loss treatment.

Compared with gastric bypass, duodenal switch may be associated with a greater risk of vitamin A and D deficiencies in the first year after surgery and of thiamine deficiency in the initial months after surgery. Patients who undergo these 2 surgical interventions may require different monitoring and supplementation regimens in the first year after surgery. This trial was registered at ClinicalTrials.gov as NCT00327912.