Vitamin D Concentration Changes after Bariatric Surgery

Bariatric surgery causes physiological and anatomical changes in the gastrointestinal tract that interfere with intestinal absorption and, consequently, with the nutritional status, especially about vitamin D. The aim of the study was to evaluate the vitamin D levels and body composition of these patients in the Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) types of surgery.

The retrospective cohort study included a population of 120 patients aged between 18 and 65 years, with class II or III obesity, undergoing bariatric surgery procedures (VSG or RYGB-type). Data were collected on the degree of obesity, age, average time since surgery, and gender. The individuals underwent a complete physical examination, measuring blood pressure, weight, height, waist, and neck circumference. In addition to calculating the percentage of loss of body weight and assessing body fat, the food frequency and physical activity of these patients were evaluated. Blood was collected, and the insulin variables, hydroxyvitamin D (25OHD), were analyzed.

There was a significant difference between groups only for PTH, total BMD, and insulin variables. A significant intragroup difference was found in the variables' body mass index (BMI) and vitamin D for the vertical sleeve gastrectomy group and BMI for the RYGB group.

The analysis between the groups of procedures, similarity in body composition and postsurgical vitamin D levels, with significant differences only for PTH, BMD, and insulin variables, demonstrates that both procedures are effective in reducing fat mass.