Vitamin D status before and after metabolic and bariatric surgery at Landspitali

INTRODUCTION: Long-term results from bariatric surgery amongst individuals with obesity is considered good in general, with regard to weight loss, complications of obesity or quality of life. However, risk of nutrient deficiency might be increased. The aim of the study was to assess vitamin D status of patients before and after metabolic and bariatric surgery at Landspitali. METHODS: Data on 25(OH)D concentration and parathyroid hormone (PTH) was retrieved from medical records for patients undergoing metabolic and bariatric surgery at Landspitali from 2001-2018 (n=539). Insufficient vitamin D status was defined as 25(OH)D concentration <45 nmol/L in 2001-2012 but <50 nnmol/L from 2013-2018, due to changes in analytical method during the study period. Vitamin D deficiency was defined as 25(OH)D <30 nmol/L for both time periods. Guidelines on supplement use are provided before discharge from the hospital and up to 18 months after surgery, RESULTS: Mean concentration of 25(OH)D before surgery was 51 nmol/L (SD 30 nmol/L) and 278 (52%) had insufficient vitamin D status, of which quarter of subjects were defined as being vitamin D deficient. Concentration of 25(OH) D increased after surgery in majority of subjects (85%). However, about third of those defined as having insufficient vitamin D status before surgery still had insufficient status 18 months after surgery. When comparing time periods, 2001-2012 and 2013-2018 it can be seen that insufficient vitamin D status was less common in the second period, although still persistent in about 25% of cases before surgery and 8.5% 18 months after surgery. CONCLUSION: Insufficient vitamin D status is relatively common before metabolic and bariatric surgery at Landspitali. In large majority of subjects, 25(OH)D concentration increased after surgery, following recomendations on supplement intake. The results highlight the need for greater emphasis on correcting possible nutrient deficiencies before surgery.