Background Bariatric surgery for severe obesity can lead to micronutrient/vitamin deficiencies. Aims To study baseline and post-surgical prevalence of vitamin D deficiency in patients undergoing bariatric surgery. Participants and Setting Patients undergoing bariatric surgery in a university teaching hospital in North West England. Methods We performed an observational cohort analysis of longitudinal data on vitamin D and related parameters in patients who underwent bariatric surgery. Patients were routinely recommended daily combined calcium and vitamin D supplementation post-surgery. Results We studied 460 patients who had completed at least 12 months post-operatively; mean (standard deviation) age was 48.0 (10.5) years, weight 144.7 (27.3) kg and body mass index 50.0 (7.6) kg/m 2 ; 292 (63.5%) underwent gastric bypass and 168 (36.5%) sleeve gastrectomy. Vitamin D level was 33.1 (23.9) nmol/L at baseline, rising to 57.1 (23.1) nmol/L at 12 months postsurgery. Whereas 43.2% had vitamin D deficiency and 34.7% insufficiency preoperatively, 8.9% and 26.7% had deficiency and insufficiency, respectively, at 12 months with similar trends up to 4 years of follow-up. There were no significant differences between procedures or sexes in vitamin D levels or sufficiency rates. Conclusion Vitamin D deficiency and insufficiency were prevalent pre-surgery and reduced significantly with routine supplementation post-surgery.

Purpose Bariatric surgery is associated with deficiencies of vitamins and minerals, and patients are routinely advised supplements postoperatively. We studied prevalence of vitamin B 12 , folate and iron deficiencies and anaemia before and after bariatric surgery over 4 years of follow-up. Materials and Methods We performed a retrospective cohort analysis of 353 people with obesity, including 257 (72.8%) women, who underwent gastric bypass (252, 71.4%) or sleeve gastrectomy (101, 28.6%) at our National Health Service bariatric centre in Northwest England. Results At baseline, mean (standard error) age was 46.0 (0.6) years, body mass index 53.1 (0.4) kg/m 2 , serum vitamin B 12 400.2 (16.4) pg/L, folate 7.7 (0.2) μg/L, iron 12.0 (0.3) μmol/L, ferritin 118.3 (8.4) μg/L and haemoglobin 137.9 (0.8) g/L. Frequency of low vitamin B 12 levels reduced from 7.5% preoperatively to 2.3% at 48 months (P < 0.038). Mean folate levels increased from baseline to 48 months by 5.3 μg/L (P < 0.001) but frequency of low folate levels increased from 4.7% preoperatively to 10.3% (P < 0.048). Ferritin levels increased from baseline to 48 months by 51.3 μg/L (P < 0.009). Frequency of low ferritin levels was greater in women (39.1%) than in men (8.9%) at baseline (P < 0.001) and throughout the study period. Haemoglobin was low in 4.6% of all patients at baseline with no significant change over the study period. Conclusion There were notable rates of haematinic insufficiencies in bariatric surgical candidates preoperatively. Our study lends further support to regular supplementation with vitamin B 12 , folic acid, and iron in people undergoing bariatric surgery.

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