Bariatric surgery has promoted weight loss and improved glycemic management in obese patients through Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG).1 Obesity plays a pivotal role in the pathogenesis of Type 2 diabetes mellitus, with an estimated 592 million people expected to be diagnosed by 2030.2 Obese patients have adipose tissue dysfunction characterized by inflammation from over-nutrition and lipid accumulation, which leads to insulin resistance3 and contributes to liver injury.4
The recently published Bariatric Surgery Patients — A Nutritional Guide reviews the impact of different bariatric surgery techniques on weight loss with resolution of blood glucose issues.5 But weight loss is not the only factor for improving Type 2 diabetes mellitus. Gut hormones, rapid transit time reducing ingested nutrient absorption, increased bile acids and alterations in the intestinal microbiome all play a role in obesity and blood glucose management following bariatric surgery.6,7
The Type 2 diabetes mellitus remission mechanisms following bariatric surgery include metabolic and lifestyle improvement, but nutritional complications also need attention because lifelong deficiencies can have a deleterious effect on health and well-being. Nutritional deficiencies prior to surgery may be aggravated by the surgical procedure, causing postoperative complications.8 More than 250,000 bariatric surgical procedures are performed in the U.S. annually, with iron deficiency anemia being one of the most common complications requiring lifelong monitoring.9-11
A random survey of 100 female Type 2 diabetes patients ages 22–64 seen for nutrition assessment prior to bariatric surgery during 2014–2017 revealed more than 50 percent had anemia (hemoglobin <12 grams per deciliter) on a complete blood count prior to surgery.17 Symptoms of anemia —including fatigue, cold hands and feet, headaches, weakness, pale skin and dizziness — that were observed during the assessment had all been written off as “incorrect eating habits” or “result of excess weight gain” by their primary-care physicians and/or diabetologists and not considered important enough to need treatment. But numerous studies have found that anemia as well as deficiencies in folate, vitamin B12 and vitamin D may be involved in poor patient prognosis post-surgery.12-15
Pre-surgery supplementation can reduce mortality rates.16 The most frequently reported nutrient deficiencies were hemoglobin, ferritin, vitamin B12, vitamin D and thiamine.17
Anemia and iron
Postoperatively, mild to moderate anemia is usually treated with dietary supplementation of iron despite the unknown cause of the anemia. Ferrous iron is preferred due to its improved absorption over ferric forms. Taking iron with a meal is preferable to improve bioavailability and tolerance.
However, calcium blocks the absorption of iron, as do coffee and tea, so counseling can encourage iron supplementation at times when these foods and supplements are not being consumed. Due to increased bone turnover in postsurgical Type 2 diabetes patients, the surgeons referring patients for nutrition assessments stress the importance of calcium supplements but fail to advise using calcium at bedtime to reduce interference with iron absorption. Nutrition counseling is not required post-surgery but should be strongly encouraged.
Patients with mild anemia may be asymptomatic, but when the anemia worsens, symptoms of fatigue and pallor, along with lab test results, indicate more aggressive treatment is required.19 Erythropoietin (EPO) has been used in several Type 2 diabetes bariatric surgery cases to stimulate production of red blood cells. Two cases in the survey mentioned above — women three and four years post-surgery — were so happy with their blood glucose management and weight loss that they failed to notice anemia symptoms until routine CBCs continued to show reduced hemoglobin and low ferritin levels.17 Alexandrou et al. reported a similar rate of anemia in both RYGB and VSG cases.20
Iron absorption occurs predominately in the duodenum,21 but since bariatric surgery reduces gastric acid secretion and pepsin, the solubility of ferric iron supplements is significantly reduced. Erythropoiesis profoundly influences iron absorption and enhances iron uptake from the gastrointestinal tract to meet nutritional needs.22 Iron is an essential trace element that is incorporated into every red blood cell’s hemoglobin molecule. The average adult produces 2 x 1011 red blood cells daily, with each cell containing more than a billion atoms of iron (each 1 ml of red blood cells contains 1 mg iron).23 Iron uptake from the diet pre-surgery is estimated at a mere 10 percent.24
When bariatric surgery patients were surveyed about their iron supplementation regimen, most replied that the side effects of the 325-mg tablet of ferrous sulphate (50–60 mg elemental iron) prescribed included constipation and hard stools before surgery, so they frequently stopped taking them within one week and never resumed after surgery. They were not aware that iron-containing foods like chicken and egg yolks would bypass the duodenum, where iron is absorbed, after surgery. None of them recalled being told they would need to monitor their iron levels for the rest of their lives.
Anemia and folate
Folate deficiency is also a potential contributor to anemia in bariatric surgery patients due to restrictive and malabsorption issues.25,26 Symptoms include macrocytic anemia, thrombocytopenia, leukopenia and glossitis. It is believed that folate is absorbed throughout the small intestine, so deficiency is induced by reduced consumption of folate-rich vegetables and fresh fruits instead of malabsorption.
Folate supplements (not folic acid) can provide necessary nutrients to convert inactive methyltetrahydrofolic acid into the active tetrahydrofolate acid needed for anemia management.
Anemia and vitamin B12
Lack of vitamin B12 is a major cause of anemia in bariatric surgery patients following biliopancreatic diversion or Roux-en-Y gastric bypass (not VSG).27,28 Vitamin B12 deficiency results from the inadequate secretion of intrinsic factor, limited gastric acidity and the bypassing of the duodenum where absorption occurs. Once the body’s stores are depleted, anemia due to lack of vitamin B12 leads to neurological and psychiatric symptoms, including memory disturbance, reduced muscle coordination and even dementia.29 Oral and intramuscular methylcobalamin is recommended due to malabsorptive procedures resulting from bariatric surgery.30
Vitamin B12 deficiency can also result from small intestinal bacteria overgrowth due to production of cobamides, biologically inactive vitamin B12 analogues.31 Pre-operative vitamin B12 deficiency needs to be considered in Type 2 diabetes when metformin and proton pump inhibitors (PPIs) are prescribed.32,33
Screening for vitamin B12 deficiency is recommended for all bariatric patients according to joint guidelines published by the American Association of Clinical Endocrinologists, The Obesity Society and American Society for Metabolic and Bariatric Surgery.34
Many patients exhibit clinical symptoms of deficiency even though vitamin B12 status is within the reference range.35 In a case of vitamin B12 deficiency, intramuscular or subcutaneous administration is the preferred route until stable levels are achieved with 1000 μg i.m./s.c. daily for five to seven days, followed by four to five weekly injections of 1000 μg.36 Intranasal and sublingual applications of vitamin B12 bypass the need for intrinsic factor, but further study in this area is needed.
Numerous case studies from the survey of Type 2 diabetes mellitus bariatric surgery patients are included in Bariatric Surgery Patients —A Nutritional Guide.5 One that highlights the importance of setting realistic expectation s is a 32-year-old female on a basal-bolus insulin regimen whose surgeon told her the Type 2 diabetes would be resolved post-surgery. Two months postsurgical lab reviews confirmed that she still had Type 2 diabetes, so she would need to continue her insulin regimen and “accept her BMI of 41” in addition to monitoring her nutritional needs.
Non-adherence to recommended dietary supplementation is a major factor in nutritional deficiencies for Type 2 diabetes patients pre- and post-bariatric surgery. This was demonstrated in the survey and reported by Modi et al., Brolin et al. and Andreu et al.37-39 Nutritional surveillance is an essential component in the management of Type 2 diabetes and bariatric surgery. If patients are to maintain a good quality of life after surgery, nutritional deficiencies — including anemia management — must be assessed on a regular basis with patient education built into postoperative protocols.
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About our expert: Betty Wedman-St Louis, PhD, RD, LD, Licensed Nutritionist & Environmental Health Specialist