January 28, 2019
3 min read

Nutritional deficiencies common before and after bariatric surgery

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For adults undergoing bariatric surgery, lifelong nutritional support is a key factor in successful outcomes. After surgery, patients are at increased risk for micronutrient deficiencies, which can result in anemia or osteoporosis, among other conditions. For many patients, nutritional challenges are present even before surgery, according to experts.

Study results presented at ObesityWeek in November showed that nearly two-thirds of adults had micronutrient deficiencies before bariatric surgery. Wah Yang, MD, surgical specialist and investigator at The First Affiliated Hospital of Jinan University in Guangdong, China, and colleagues reported that among 414 of 668 Chinese adults going in to Roux-en-Y gastric bypass and sleeve gastrectomy procedures, 25.1% had thiamin (vitamin B1) deficiency, 21.4% were deficient in vitamin C, and 19.7% had low levels of vitamin E. Micronutrient deficiencies were also common with 29.1% of patients deficient in zinc and 14.2% in transferrin.

The study highlighted the importance of nutrition support for this patient population, as patients showed improved levels of vitamins B1, C and D, and of ferritin with supplements 1 year after surgery (P < .05), according to Yang.

Short-term concerns

Nutritional support can be crucial to the success of bariatric surgery, even for patients who are not experiencing symptoms of vitamin deficiency, according to Sangeeta Kashyap, MD, associate professor of medicine at Cleveland Clinic Lerner College of Medicine and staff physician in the department of endocrinology at Cleveland Clinic.

Sangeeta Kashyap

“It is very important for these patients to, at least twice a year, get their vitamin levels checked because sometimes they do not have any symptoms,” Kashyap told Endocrine Today. “I think [vitamin deficiency] is under-recognized because [after] losing the weight and improvements of comorbidities, patients generally feel good after having the surgery. … They do not understand that there are permanent changes to their bodies, and they are not able to absorb and process vitamins.”

Liz Goldenberg, MPH, RDN, CDN, program coordinator of gastrointestinal, metabolic and bariatric surgery at NewYork-Presbyterian Hospital, agrees.

“Both in my experience in New York City as well as my reviews of the literature of nutrient deficiencies relating to bariatric surgery in the U.S., remarkable abnormalities in nutritional laboratory values are present both before and after surgery,” Goldenberg told Endocrine Today.

Liz Goldenberg

Goldenberg presented a case study during ObesityWeek of a patient who experienced thiamin (B1) deficiency after sleeve gastrectomy, the most common micronutrient deficiency reported in the study by Yang and colleagues. Thiamine deficiency is a serious risk for this patient population, Goldenberg said, because the body loses about half of the thiamine contained in tissues every 10 to 20 days. Patients who vomit after gastric surgery are at increased risk for thiamine depletion. Over time, this can lead to Wernicke encephalopathy.

Goldenberg said additional key nutrients to track include zinc, vitamin A and folic acid.

Long-term needs

Although the study by Yang and colleagues found no significant long-term (more than 2 years after surgery) results and no difference according to surgical type, Goldenberg and Kashyap said patients must remain vigilant about nutrition over time.

“For example, the body has the ability to store vitamin B12 for a long period of time, perhaps years; thus, vitamin B12 status immediately following sleeve surgery may be normal,” Goldenberg said. “However, this operation removes the part of the stomach responsible for secreting intrinsic factor, which is needed for vitamin B12 to be absorbed in the ilium. A vitamin B12 deficiency and/or pernicious anemia may develop years following surgery.”

After bariatric surgery, patients may have trouble with absorption of iron, vitamin D and calcium, leading to loss of bone density that can continue for years, according to Kashyap.

“Even 5 years after having surgery, we can see that there’s in an increase in bone turnover markers, which tells us that … the bone is being resorbed constantly, even after the initial weight loss. You can still see changes in bone metabolism for years after,” Kashyap said. “This is [a] really long [time] after the weight loss.”

Goldenberg and Kashyap warned of the dangers of developing metabolic bone disease in the long term for patients who are not supplementing these crucial micronutrients.

Overcoming common obstacles

Goldenberg and Kashyap said it is important for patients to see a specialist to manage nutrition. Between monitoring comorbidities and managing a patient’s weight, a physician may not have enough time to address nutritional needs.

“Patients are getting the surgery to make themselves healthier, but if they do not follow the nutrition guidelines, they could be doing themselves a real disservice,” Kashyap said. “That is the bottom line.”

Patients who are not used to taking supplements daily may struggle for the first few months after surgery. Because most programs advise against swallowing large pills whole, patients may need to crush, crumble, or split pills, or take supplements in chewable, liquid or powdered form, Goldenberg said.

Kashyap recommended trying compounded vitamins to cut down on the number of pills. Some additional tips from Goldenberg include using a weekly pill box, setting up cellphone reminders and attending support groups to help patients stay on track. – by Amanda Alexander


Yang W, et al. A256. Presented at: ObesityWeek 2018; Nov. 11-15, 2018; Nashville, Tenn.

For more information:

Liz Goldenberg, MPH, RDN, CDN, can be reached at elg2016@med.cornell.edu.

Sangeeta Kashyap, MD, can be reached at kashyas@ccf.org.

Disclosures: Goldenberg, Kashyap and Yang report no relevant financial disclosures.