Micronutrient Deficiencies in Obese Patients and Risk of Postoperative Fistula: A Forgotten Link in Bariatric and Metabolic Surgery

Micronutrient deficiencies are commonly observed in patients with obesity and may persist or worsen following bariatric and metabolic surgery. Emerging evidence suggests that micronutrients play a fundamental role in tissue repair, collagen synthesis, immune function, and inflammatory regulation processes that are critical in postoperative healing. Therefore, deficiencies in these nutrients could be pivotal in understanding and preventing postoperative complications. However, the potential link between preoperative micronutrient status and the development of postoperative complications, such as anastomotic or gastric fistula, remains underexplored. This narrative review aims to investigate the correlation between specific micronutrient deficiencies (e.g., vitamin C, zinc, selenium, vitamin A, and iron) and the incidence of fistula after bariatric surgery. We will discuss the underlying biological mechanisms, clinical evidence, and possible preventive strategies, including preoperative screening and targeted supplementation. Our aim is to highlight the often-overlooked micronutrient deficiency as a risk factor in patients undergoing bariatric surgery, both in the pre- and postoperative periods, and to propose a more comprehensive approach to patient assessment and management.