Monitoring for micronutrient deficiency after bariatric surgery-what is the risk?

Background: Bariatric surgery may increase the risk of micronutrient deficiencies; however, confounders including preoperative deficiency, supplementation and inflammation are rarely considered.
Objective: To examine the impact of bariatric surgeries, supplementation and inflammation on micronutrient deficiency.
Setting: Two public hospitals, Australia.
Methods: Participants were recruited to an observational study monitoring biochemical micronutrient outcomes, supplementation dose, inflammation and glycaemic control, pre-operatively and at 1-3, 6 and 12 months after gastric bypass (GB; Roux-en-Y Gastric Bypass and Single Anastomosis Gastric Bypass; N = 66) or sleeve gastrectomy (SG; N = 144). Participant retention at 12 months was 81%.
Results: Pre-operative micronutrient deficiency was common, for vitamin D (29-30%), iron (13-22%) and selenium (39% GB cohort). Supplement intake increased after surgery; however, dose was <50% of target for most nutrients. After SG, folate was vulnerable to deficiency at 6 months (OR 13 [95% CI 2, 84]; p = 0.007), with folic acid supplementation being independently associated with reduced risk. Within 1-3 months of GB, three nutrients had higher deficiency rates compared to pre-operative levels; vitamin B1 (21% vs. 6%, p < 0.01), vitamin A (21% vs. 3%, p < 0.01) and selenium (59% vs. 39%, p < 0.05). Vitamin B1 deficiency was independently associated with surgery and inflammation, selenium deficiency with improved glycaemic control after surgery and inflammation, whilst vitamin A deficiency was associated with inflammation only.
Conclusion: In the setting of prophylactic post-surgical micronutrient prescription, few nutrients are at risk of de novo deficiency. Although micronutrient supplementation and monitoring remains important, rationalising high-frequency biochemical testing protocols in the first year after surgery may be warranted.
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