RESUMEN
BACKGROUND: Hypovitaminosis D is common, before and after gastric bypass surgery. The prevalence of hypovitaminosis D in a large group of candidates for bariatric surgery in Brazil and South America has not been studied. OBJECTIVE: To evaluate the prevalence of hypovitaminosis D and associated factors in patients undergoing bariatric surgery in Southern Brazil. MATERIALS AND METHODS: Cross-sectional study involving all patients presenting for bariatric surgery at Hospital de Clínicas de Porto Alegre, from January 2013 to June 2018. Data were extracted from the patients' electronic medical records. Patients who were taking multivitamin supplements or vitamin D supplements, who had renal insufficiency, or had missing data for 25(OH) vitamin D [25(OH)D] levels were excluded. RESULTS: A total of 291 patients were included. Mean subjects' age was 44.9 (SD 10.7) years, and BMI 49.3 (SD 8.3) kg/m2; 76.6% of the study patients were women, and 87.3% were white. More than half the patients (55.3%) were vitamin D deficient (serum 25(OH)D ≤ 19.9 ng/ml), and 37.1% had insufficient levels (20-29.9 ng/mL). Mean vitamin D level was 19.2 ng/mL (SD 7.6). An inverse correlation was found between 25(OH)D levels and BMI. Vitamin D deficiency was more prevalent in patients with higher BMI [PR 1.02; CI 95% (1.00-1.03)], higher fasting glucose [PR 1.01; CI 95% (1.00-1.01)], in nonwhite patients [PR 1.58; CI 95% (1.30-1.92)] and during autumn/winter season [PR 1.41; CI 95% (1.14-1.75)]. CONCLUSIONS: Prevalence of vitamin D insufficiency and deficiency is very high among patients presenting for bariatric surgery in Southern Brazil, and the known associated factors are confirmed in this population.