Maintaining Mineral and Vitamin Status Within the Reference Range in Patients Undergoing Mini Gastric Bypass (OAGB/MGB): Results of a Retrospective Study

Background: Nutritional deficiencies are common during the first postoperative year after mini gastric bypass (OAGB/MGB). This retrospective study evaluated the adequacy of a Food for Special Medical Purposes formulated for bariatric patients in maintaining mineral and vitamin status after OAGB/MGB. Methods: Patients who underwent laparoscopic OAGB/MGB at the Nutrition Clinic of Koelliker Hospital (Turin, Italy) between January 2023 and March 2024, aged 18–65 years and taking the product at 2 sachets/day for 12 consecutive months within a structured postoperative nutritional program, were retrospectively analyzed. Anthropometric and biochemical parameters were assessed at baseline (T0), 6 months (T6), and 12 months (T12) and compared using nonparametric repeated-measures tests. Results: Twenty-five patients were included (9 males, 36%; 16 females, 64%; mean age 52.8±7.2 years; preoperative BMI 46.4±5.8 kg/m²). At 12 months, mean weight loss was 34% and excess weight loss 74%. Vitamin D deficiency (<30 ng/mL) declined significantly from 79% at baseline to 28% at T6 and 16% at T12 (p<0.001). Vitamin B12 increased significantly within the first 6 months and then stabilized (p=0.0056), with only one residual deficiency at T6. Folate levels did not change significantly (p=0.099), though deficient/borderline values fell from 40% to 4%. Hemoglobin and mean corpuscular volume remained stable. Serum iron improved significantly only at 12 months (p<0.001), while ferritin declined significantly, mainly between T0 and T6 (p=0.046), remaining above the deficiency threshold on average. Conclusions: In this real-world series, the tested product combined with structured nutritional follow-up was associated with maintenance or improvement of most micronutrient parameters during the first year after OAGB/MGB, although ferritin remained a critical parameter requiring continued surveillance.