High vitamin D deficiency rate in metabolic inpatients: is bariatric surgery planning found guilty?

Background: High rates of vitamin D insufficiency are usually found in obese patients, even before any malabsorptive bariatric surgery. It is not clear whether they lack vitamin D because of different food intake, different solar exposure, or different storage pathways or bioavailability in adipose tissue. To better understand vitamin D deficiency, we studied different categories of inpatients.

Methods: We collected clinical and biological data from 457 consecutive inpatients during a year: 217 nonobese diabetic patients, 159 obese nonsurgical diabetic patients, 46 obese surgical nondiabetic patients, and 35 obese surgical diabetic patients. Statistically significant differences between two mean 25-hydroxyvitamin D (25(OH)D) levels were defined at the 5 % level using a Z-test.

Results: Vitamin D deficiency was found in 69 % of the patients, while 24 % had a normal level and 7 % an optimal level. A significant difference was found between obese (25(OH)D = 40.3 nmol/l) and nonobese patients (25(OH)D = 46.8 nmol/l). Patients undergoing bariatric surgery were not different from the other obese patients.

Conclusion: No significant difference in 25(OH) vitamin D level could be demonstrated between obese patients before bariatric surgery and obese patients with no obesity surgery project. No difference was found between our Parisian obese population and a Spanish obese population, which benefits from a better solar exposure. Both findings suggest that obesity itself is the link with vitamin D deficiency, independently from behavioral differences.