Patients face vitamin deficiencies years after bariatric surgery

By Dr. Priyom Bose, Ph.D.Reviewed by Lauren HardakerJul 30 2025

A new review uncovers why dangerous vitamin deficiencies, from vision loss to life-threatening complications, are harming patients years after weight loss surgery, and how better follow-up could save lives.

Study: Nutritional Deficiencies Following Bariatric Surgery: A Rapid Systematic Review of Case Reports of Vitamin and Micronutrient Deficiencies Presenting More Than Two Years Post-Surgery. Image credit: New Africa/Shutterstock.com

Although an effective treatment for severe obesity, bariatric surgery may lead to nutritional deficiencies. Researchers performed a systematic review to understand which nutritional deficiencies occur post-bariatric surgery, their contributing factors, and their prevention strategies. This review has been published in Clinical Obesity.

Bariatric surgery: An effective intervention for severe obesity

According to a 2022 report, one in every eight people in the world was living with obesity. Obesity is a complex disease characterized by excessive fat accumulation in the body that has adverse health effects. Individuals with severe obesity are often recommended for a bariatric surgery, which is commonly known as weight loss surgery that involves altering the digestive system.

Bariatric surgery is a cost-effective intervention whose benefits extend beyond weight loss. For example, this surgery has proved to be beneficial in alleviating type 2 diabetes, improving hypertension, and reducing cardiovascular ailments. Despite the benefits, bariatric surgery is also linked to certain complications, such as nutritional deficiencies. Previous studies have shown that micronutrient deficiencies can occur even many years after surgery.

Considering the complications of bariatric surgery, the European Association for the Study of Obesity (EASO) has recommended lifelong post-operative follow-up. They advise patients to take micronutrient supplementation daily and be frequently screened for nutritional deficiencies. In England, the National Institute for Health and Care Excellence (NICE) guidance requires patients to undergo follow-up from specialist bariatric services for at least 2 years. Following this, patients are advised to undergo nutritional screening and receive appropriate supplementation under a shared care model.

Despite the recommendations from EASO and NICS, only around 5% of patients receive appropriate long-term follow-up in primary care. Lack of access to specialist services, funding, and inadequate training for care staff contribute to inadequate post-operative care. This leaves patients vulnerable to nutritional deficiencies, which may significantly impact their health.

Previous studies have identified multiple deficiencies at long-term follow-up post-bariatric surgery, including vitamin E, D, A, K, and B12. However, the current review emphasizes that vitamin D deficiency was the most frequently reported (23 cases), followed by vitamin A (15) and Copper (14), and that common deficiencies such as iron and anaemia are likely underrepresented because case reports tend to focus on rare or more severe outcomes.

It is vital to investigate the case reports of real patients who underwent the surgery to uncover the nutritional deficiencies and issues experienced by patients during follow-up. This strategy will help reveal the factors contributing to deficiencies and variability in treatment.

About the review

The current systematic review included all adults who underwent different types of bariatric surgery, such as gastric band, sleeve gastrectomy, gastric bypass, and duodenal switch, and developed post-surgical nutrient deficiency of one or more of the micronutrients that are listed in national guidance as requiring monitoring. Less common procedures, such as jejunoileal bypass, vertical banded gastroplasty, one-anastomosis gastric bypass, and combinations like sleeve gastrectomy with duodenal switch, were also represented in a few cases.

This study only included participants who underwent bariatric surgery ≥ 2 years ago because patients are transferred from specialist services to primary care during this period. All relevant articles, published from January 2000 until January 2024, were obtained from MEDLINE and EMBASE databases.

Impact of vitamin deficiencies in patients after bariatric surgery

A total of 83 cases were obtained that met the inclusion criteria, reported in 74 articles. Most selected cases were from the USA, followed by Italy, Belgium, Spain, the UK, France, Greece, Australia, Germany, Israel, Austria, Denmark, Taiwan, Brazil, Canada, and the Netherlands.

Approximately 84% of the participants were female, and 16% were male, aged between 22 and 74. It must be noted that the case studies selected in this review also included pregnant, postpartum, and breastfeeding women. Some of these cases involved serious outcomes for infants, including intracranial hemorrhage, microphthalmia, prematurity, and even death, highlighting the severity of untreated deficiencies in this group.

Most selected participants underwent Roux-en-Y gastric bypass (RYGB), followed by biliopancreatic diversion (BPD), gastric bypass, a laparoscopic gastric band, duodenal switch, and jejunoileal bypass. However, a limited number of patients also underwent sleeve gastrectomy, anastomosis gastric bypass, vertical banded gastroplasty, gastroileal bypass, sleeve gastrectomy, and duodenal switch. The period since surgery ranged from 2 to 40 years.

Out of 83 cases, 65 reported that patients developed a single deficiency that presented complaints, while others documented the development of multiple deficiencies. Among the 65 cases, patients exhibited deficiencies in vitamin A, D, copper, zinc, vitamin B12 and folate, thiamine, and selenium.

Patients with vitamin A deficiency often develop ophthalmological symptoms, such as night blindness, visual deterioration, corneal ulcer, and eye pain and sensitivity. These patients received vitamin A as oral supplements, intramuscular (IM) replacement, or intravenous (IV) replacement via total parenteral nutrition (TPN). Some patients were treated with vitamin A eye ointment or other ocular treatments.

Patients with copper deficiency also exhibited vitamin A, iron, zinc, vitamin D, and vitamin B6 deficiency. These patients developed chronic liver failure, along with neurological (e.g., neuropathic pain, paraesthesia, weakness, sensory loss, ataxia, gait disturbance, and falls) and ophthalmological (e.g., loss of vision and blurred vision) symptoms. Treatment with oral micronutrient supplements exhibited a positive effect for these deficiencies.

Some patients had only Vitamin D deficiency, while others reported additional vitamin deficiencies. These patients more frequently develop musculoskeletal symptoms, such as joint and bone pain, decreased mobility, muscle weakness, osteoporosis, and secondary hyperparathyroidism. Patients were treated with vitamin D supplementation via different routes, formulations, and dosages, though inadequate dosing and misdiagnosis were frequent contributing issues.

Patients with zinc deficiency frequently develop dermatological conditions, and those with vitamin B12 and folate deficiencies suffer recurrent erythematous ulcers, shortness of breath, and fatigue. Thiamine deficiency causes Wernicke's encephalopathy and neurological signs. None of the patients exhibited selenium alone as the primary deficiency; however, it was present as one of several deficiencies.

Pregnant and postpartum women mainly developed vitamin A, K, B12, and zinc deficiencies, which were found to affect fetal growth and development.

A nutritionally unbalanced diet, insufficient vitamin supplementation, excessive alcohol intake, delayed diagnosis, inadequate follow-up, lack of health professional knowledge, and insufficient patient education were identified as factors that contribute to vitamin deficiency and adverse health effects after bariatric surgery.

The review stresses that some deficiencies, when not promptly recognized, resulted in permanent disability or even death, illustrating the importance of early detection and intervention. The study highlights the need for early identification and management of deficiencies to prevent patients from unwanted outcomes.

Download your PDF copy now!