Vitamin B12 supplementation orally and intramuscularly in people with obesity undergoing gastric bypass.

PURPOSE: Although bariatric surgery can facilitate weight loss and improve many diseases, it impairs the absorption of many vitamins and micronutrients. Vitamin B12 is important for these patients and should be controlled and supplemented postoperatively. The aim of this paper is to compare serum vitamin B12 levels in two forms of supplementation (oral vs. intramuscular) for 6 months after gastric bypass. METHODS: In a prospective controlled cohort study, people with obesity patients undergoing gastric bypass received vitamin B12 supplementation either orally or intramuscularly. The patients were followed for 6 months, receiving serial doses of vitamin B12 and methylmalonic acid assessment at 6 months. RESULTS: A total of 53 patients were divided into two homogeneous groups: an oral group (n=24) and an intramuscular group (n=29). Serum vitamin B12 was measured preoperatively and postoperatively at 1, 2, 3, and 6 months. Serum methylmalonic acid was measured at 6 months. At each point, the serum vitamin B12 level remained within reference values in both groups, although it was higher in the oral group (p<0.001). Methylmalonic acid also remained within reference values in both groups, with no significant differences. CONCLUSION: Despite the anatomical and functional alterations that impair vitamin B12 absorption after gastric bypass, oral vitamin B12 supplementation was as effective as intramuscular in this population.