Bariatric surgery: Postoperative nutritional management

INTRODUCTION — The goals of bariatric operations include maximizing weight loss and maintaining or achieving nutritional health while preventing micronutrient deficiencies and lean body mass loss [1,2]. Deficiencies of micronutrients following bariatric surgery can arise from several mechanisms that include preoperative deficiency, reduced dietary intake, malabsorption, and inadequate supplementation. Since obesity is a risk factor for malnutrition and micronutrient deficiencies, all patients should be screened and deficiencies corrected prior to surgery. The postoperative diet and texture progression, micronutrient deficiencies, and their management are reviewed here.

Bypass procedures, such as Roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion with duodenal switch (BPD/DS), are known to cause micronutrient malabsorption [1,3-8]. The sleeve gastrectomy (SG), which is the most commonly performed bariatric procedure in certain regions, does not involve intestinal bypass but can still lead to certain nutritional deficits. Any bariatric procedure can result in malnutrition if a proper diet is not followed. The specific bariatric procedures, indications, and outcomes are reviewed elsewhere and include the following topics:

●(See "Bariatric procedures for the management of severe obesity: Descriptions".)

●(See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

●(See "Bariatric operations: Early (fewer than 30 days) morbidity and mortality".)

●(See "Bariatric surgery: Postoperative and long-term management".)

●(See "Outcomes of bariatric surgery".)

●(See "Laparoscopic Roux-en-Y gastric bypass".)

●(See "Laparoscopic sleeve gastrectomy".)

DIET AND TEXTURE PROGRESSION — The diet after bariatric surgery is based upon a staged approach with emphasis on nutritional needs at each stage of healing and weight loss. Additionally, consideration is given to the texture and volume of food that patients can tolerate [9]. While all post-bariatric surgery patients will benefit from a well-planned dietary advancement that ensures proper healing of the surgery and develops lifelong healthy eating habits, such plans have to take into consideration a large variation in food tolerance depending upon the nature of the bariatric operation (eg, size of remnant stomach, presence of gastrojejunostomy, etc) (table 1 and table 2).

Early (postoperative) diet — Although postoperative diet plans are generally surgeon or institution specific, the following approaches to the nutritional management of the postoperative bariatric patient are generalizable to most patients [1,9,10]. Patients are managed similarly after Roux-en-Y gastric bypass and sleeve gastrectomy (table 1) but somewhat differently after laparoscopic adjustable band (table 2).

Stage 1 and 2 diet: Hydration and liquids — The immediate postoperative diet should emphasize hydration and protein intake. Patients are started on a clear liquid diet (stage 1) and, after a brief period, are advanced to full liquids and possibly pureed foods, which they will consume for up to several weeks after the operation (stage 2 diet). Early hydration and consumption of protein and carbohydrates to meet metabolic needs are essential, and the stage 2 diet helps to avoid irritation to the surgical areas of the digestive tract.

Many programs discharge patients from the hospital on a stage 2 diet that includes liquid sources of protein that also contain small amounts of carbohydrate. Other programs discharge patients on a pureed diet. Patients should be taught to recognize signs and symptoms of dehydration. All patients should receive preoperative education that focuses on their postoperative nutritional needs, including guidelines regarding the consumption of an adequate amount of clear and full liquids daily to maintain hydration and urine output. Surgical patients should be provided educational materials, shopping lists, and sample meal plans of when they should be consuming clear and full liquids and how much. Such guidelines should be reinforced through postoperative discharge instructions.

Stage 3 diet: Soft solid foods — Approximately 10 to 14 days after surgery, as the gastrointestinal tract heals and patients are able to tolerate more solid-textured foods, the diet is advanced to include soft solid foods with an emphasis on protein sources, some carbohydrates, and fiber (eg, fruits and vegetables). Patients can advance their diet (texture and portions) as tolerated as long as they follow guidelines for the stage 3 diet. At this stage, pureeing food is not necessary for most patients, except those who still have difficulty chewing.

Throughout all of the diet stages, patients should be counseled to consume adequate fluid to prevent dehydration. Enhanced Recovery After Surgery (ERAS) guidelines recommend that patients consume >1.5 L (50 oz) fluids per day to prevent dehydration [11]. Patients should be counseled on adequate fluid intake, as it can be difficult for most patients to consume this much due to the sleeve or pouch capacity, decreased appetite, and increased satiety.

Food tolerance varies widely among patients. Patients are advised to eat slowly, chew food extensively, stop eating as soon as they reach satiety, and avoid taking food and beverages at the same time. Vomiting and epigastric discomfort frequently occur if food is ingested too quickly or when the patient eats more than the stomach pouch or sleeve can hold. During the first few months after surgery, most patients learn to recognize the early satiety provided by a small gastric volume. Because overeating can result in vomiting or nausea, most patients quickly learn to control portion sizes and food reactions. Guidance by an experienced bariatric registered dietitian is strongly advised during the transition between diet stages, per the clinical practice guidelines [9].

Stage 4 diet: Solid foods — Patients typically transit to the stage 4 diet, or regular textured foods, between six to eight weeks following surgery [9]. Because of the wide variability in the rate of weight loss, healing, food tolerance, and the amount of food patients can consume, it can be variable when a patient will reach this stage. Some programs do not have a stage 4 diet, as most patients already tolerate regular foods by stage 3. The transition through the diet stages should be based on individual tolerance.

As patients are advancing their diet, they should be encouraged to consume a healthy, balanced diet. The purpose of nutrition care after surgical weight loss procedures is to ensure adequate energy and nutrients to support tissue healing after surgery and support preservation of lean body mass during extreme weight loss. Foods and beverages must minimize reflux and promote early satiety while maximizing weight loss or aiding in weight maintenance. A heathy, balanced diet should consist of lean proteins, fruits and vegetables, whole grains, low-fat dairy, and healthy fats. The intake and portions of the healthy diet will increase over time as patients are advancing their diet.

Micronutrient supplementation is started at hospital discharge with chewable or liquid vitamins initially; by three months, most patients can tolerate regular vitamin pills. The recommended postoperative micronutrient supplementation following a Roux-en-Y gastric bypass (RYGB) or gastric sleeve procedure is discussed separately (table 3) [2,10,12-14]. (See 'Micronutrient deficiency, supplementation, and repletion' below.)

In the past, patients were instructed to take one or two pills of multivitamin a day after bariatric surgery. However, there is wide variability in the formulations of multivitamins, and most do not contain enough elemental iron or calcium to meet the needs of bariatric patients. Thus, a "one size fits all" approach does not work for every bariatric surgical patient; supplementation needs to be tailored to each individual's nutritional intake and status based upon regular review of blood chemistries. At a minimum, the supplement should contain the recommended daily allowance (RDA) amounts for vitamin K, biotin, zinc, thiamine, vitamin B12, folic acid, iron, and copper [15]. The minimum amounts of daily vitamins and minerals required to prevent deficiency are summarized in this table (table 3). (See 'Postsurgical screening' below and 'Micronutrient management' below.)

Long-term diet and habit changes — Long-term eating habits are in part determined by the patient's motivation, willingness, and ability to adhere to a healthy diet. Dietary intake longer-term is also dependent upon the type of bariatric procedure performed (see "Bariatric procedures for the management of severe obesity: Descriptions"):

Long-term diet and habit changes also include physical activity. Unless specifically contraindicated, patients should be advised to incorporate at least some amount of physical activity, with a target of moderate aerobic physical activity. Physical activity goals are a minimum of 150 minutes per week with a goal of 300 minutes per week, including strength training two to three times per week. Patients should be cautioned about performing high levels of activity within the first year of surgery, as their calorie and nutrition intake is very low.

Roux-en-Y gastric bypass — Due to the changes in both the pouch size and gut hormone signaling, patients may not feel physical hunger early after RYGB, and, when they do eat, they experience early satiety. As weight stabilizes and the need for external calories increases, sensations of hunger and satiety awareness will return; patients may also develop food intolerances and aversions [16-18].

Learning how to choose healthy foods, avoid skipping meals, and prepare meals and snacks on a daily basis is part of the new skills and goals all patients must learn. Patients may need continued reminders that the surgery has changed their body but not the environment. Frequent education, emotional support, and counseling sessions with a registered dietitian experienced with bariatric surgery are essential.

●Food aversions – Food aversions may develop during the transition phase from liquids to soft foods to a full diet, especially if there is prolonged vomiting associated with eating. For patients who enjoyed food variety prior to the surgery, the loss of food variety can result in anger and frustration. These patients will often complain that they experience anxiety and fear when eating. Reassurance and empathy is essential to help the patient overcome food intolerances.

By six months, most patients are able to tolerate most foods and tend to eat three small meals, with or without the inclusion of planned snacks, per day. If vomiting persists or emerges, an evaluation should be performed for anatomical etiologies (eg, ulcer, stricture) and/or pregnancy. Such patients with food aversions may express "buyer's remorse" and may request extensive investigations for problems with the gastric pouch. Reassurance about the ability of the pouch to tolerate a wide variety of foods with time is necessary.

●Dumping syndrome – This may occur to varying degrees, but it usually results in nausea, weakness, sweating, faintness, and possibly diarrhea soon after eating within the first few years after surgery. These symptoms intensify when highly refined foods with simple sugars (eg, sweets) are consumed, leading to feelings of weakness and extreme fatigue. (See "Bariatric operations: Late complications with subacute presentations", section on 'Dumping syndrome' and "Postgastrectomy complications", section on 'Dumping syndrome'.)

●Food intolerances – Food intolerances may develop, especially to red meat, and patients may choose a more vegetarian-based diet. However, fresh fruits and vegetables are generally well tolerated.

●Constipation – Another area of concern for both RYGB and sleeve gastrectomy (SG) is constipation. Constipation may occur due to many factors, including pain medication, a high-protein diet, and low intake of grains or high-fiber foods due to reduced stomach capacity. Patients should speak with their registered dietitian or medical provider about the use of fiber supplements, stool softeners, or laxatives to help relieve constipation. Persistent and severe gastrointestinal symptoms (eg, nausea, vomiting, abdominal pain, diarrhea, and constipation) warrant evaluation with imaging studies [9].

●Vitamin and mineral supplementation – Patients who have undergone bariatric surgery may require lifelong vitamin and mineral supplementation. Laboratory testing of nutritional status, scheduled at regular intervals based on the bariatric procedure, is required to permit adjustments to the standard supplementation regimens [2]. (See 'Micronutrient management' below.)

●Long-term diet recommendations – A well-balanced diet containing all of the essential nutrients is recommended for continued good health and weight maintenance. Resources that may help patients with developing a lifelong healthy postoperative diet include:

•My Plate

•DASH Diet

•The Vegetarian Resource Group

●Maintenance – Obesity is a chronic condition, and although surgery has a strong influence on hunger and satiety, hunger cues remain pervasive in today's environment. All patients should be encouraged to participate in ongoing support groups, self-monitoring, and/or mobile technologies to improve weight loss and cardiometabolic risks after bariatric procedures. Patients should follow up frequently with a registered dietitian for the first year or until weight maintenance. American Society for Metabolic and Bariatric Surgery (ASMBS) guidelines suggest that patients follow up with a registered dietician at months 1, 3, 6, 9, and 12 in the first year after surgery. Once the patient is weight stable, the frequency of follow ups may decrease; if some weight is regained, the patient should return to see the registered dietitian more frequently [9].

Sleeve gastrectomy — SG resects the greater curvature of the stomach including the fundus and promotes rapid gastric emptying, accelerated transit of nutrients into the duodenum and proximal intestine, and favorable changes to gut microbiome [19]. SG also changes gut hormone signaling by reducing fasting and postprandial ghrelin and augmenting nutrient-stimulated glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) release [19-21]. The mechanism of weight loss and resultant comorbidity improvement seen following SG may be related to gastric restriction or to neurohumoral changes observed following the procedure due to the gastric resection or some other unidentified factors [2].

Since food tolerances vary greatly among individuals who have RYGB or SG, most programs follow the same diet advancement and recommendations post-SG as for post-RYGB; close monitoring with a registered dietitian nutritionist during the diet stage transitions can be helpful to patients experiencing food intolerances or who may be struggling to stay adequately hydrated.

Nutritional recommendations for macronutrients after SG are similar to those after RYGB, although exact needs are not clearly defined and may need to be individually assessed [10].

●Food aversions – Following SG, patients may complain of acid reflux symptoms. Given the limited stomach volume, the decreased motility of food through the sleeve during the healing process, and the preservation of stomach acid, patients may experience acid reflux if they eat too quickly or too much. Although reflux is a common complaint in the early postoperative period after SG, by six months most patients have learned how to avoid it.

●Food intolerances – Food intolerances seem to be much less common after SG than after RYGB; however, as with the bypass, postoperative food intolerances and/or aversions vary widely among patients.

●Vitamin and mineral supplementation, long-term diet recommendations, avoidance of constipation, and maintenance are the same as described for patients with an RYGB. (See 'Micronutrient management' below.)

Laparoscopic adjustable gastric band — Laparoscopic adjustable gastric banding (LAGB) is now very uncommon, comprising about 1 percent of all bariatric procedures performed in the United States [22]. Patients who have undergone LAGB will generally resume a normal diet soon after surgery since the initial band is placed deflated. Rarely, patients may experience vomiting before the band is filled, if solid foods are ingested in large boluses or without adequate chewing.

The first band tightening usually occurs around six weeks after surgery. With gradual band tightening, which occurs at four- to six-week intervals during the first one to two years after surgery, patients begin to feel satiety at smaller meal sizes and learn to chew food more thoroughly.

Common determinants for a band fill include assessment of the level of hunger before meals, level of satiety after meals, amount of weight loss or gain, amount of food a patient is able to eat in one sitting, and if a patient is vomiting. A well-adjusted band, in combination with exercise and appropriate food choices, will initially lead to weight loss of approximately 1 to 2 lbs per week. Patients should be able to eat most solid foods; restriction should be just enough to allow smaller meals to cause and maintain satiety.

Aggressive tightening of the band may result in frequent vomiting, which may ultimately steer the patient to maladaptive eating behavior. Over time, significant dilation of the esophagus similar to that seen in achalasia can occur. Furthermore, patients with an overly tight band may give up eating healthy solid foods and progressively rely on soft or liquid foods (eg, milkshakes) or crunchy foods such as cookies or chips, which are better tolerated. Unfortunately, such foods tend to be calorie dense and nutrient poor and often do not provide adequate satiety, as they rapidly empty from the pouch. When this occurs, weight loss can be suboptimal, and patients become frustrated with their inability to eat substantial foods.

Removal of band fluid in a band that is too tight frequently allows patients to again eat healthy foods, and weight loss is often observed despite loosening of the band. If esophageal dilation is noted, a follow-up study should be obtained six to eight weeks later to confirm return of the esophagus to normal caliber. Persistence of nausea and vomiting after removal of fluid in the band may indicate band slippage or gastric prolapse and should be investigated aggressively. (See "Bariatric operations: Late complications with subacute presentations".)

Although micronutrient deficiencies are not commonly seen after LAGB, folate deficiency has been observed. Thus, folate should be routinely monitored, especially in women of childbearing age. Persistent vomiting in a band patient should be aggressively treated with band deflation and surgical intervention if necessary, in order to reduce the risk of acute thiamine deficiency or mechanical injury to the stomach or esophagus. (See 'Folate' below and 'Vitamin B1 (thiamine)' below and "Fertility and pregnancy after bariatric surgery".)

Biliopancreatic diversion/duodenal switch — The biliopancreatic diversion (BPD) with a duodenal switch (BPD/DS) is less commonly performed than SG and RYGB and can be associated with substantial malabsorption of macronutrients and micronutrients [22].

This malabsorption leads to diarrhea and risks for protein and calorie malnutrition in addition to severe deficiencies in micronutrients, including fat-soluble vitamins. Again, vitamin and mineral laboratory evaluations should be performed annually for life.

Some of the common complaints following BPD±DS include:

●Dumping syndrome – This is rare after BPD/DS since the pylorus remains intact. However, it may occur after BPD without DS, resulting in nausea, weakness, sweating, faintness, and possibly diarrhea soon after eating. These symptoms get worse when highly refined foods with simple sugars (eg, sweets) are consumed, leading to feelings of weakness and extreme fatigue. (See "Evaluation of postprandial symptoms of hypoglycemia in adults without diabetes".)

●Osteoporosis – Osteoporosis is common due to malabsorption of calcium and vitamin D. (See "Pathogenesis of osteoporosis" and "Screening for osteoporosis in postmenopausal women and men".)

●Foul-smelling stools and diarrhea – Foul-smelling stools and diarrhea that occur can result in malabsorption of protein; fat; calcium; iron; and vitamins B12, A, D, E, and K. (See "Overview of nutrient absorption and etiopathogenesis of malabsorption" and "Approach to the adult patient with suspected malabsorption" and "Overview of the treatment of malabsorption in adults".)

●Kwashiorkor – Severe malnutrition, kwashiorkor, is a potentially life-threatening form of protein malnutrition. While protein digestion is not impaired after RYGB, BPD/DS patients are at risk of protein malnutrition because of the great degree of malabsorption; approximately 27 percent of protein is not absorbed at 24 to 36 months after BPD [23,24]. The increased loss of endogenous nitrogen may play a significant role in the development of protein-energy malnutrition after the procedure. Protein intake of 1.5 to 2.0 g of protein/kg ideal body weight per day may be required, making the average protein requirement per day approximately 90 g/day [10]. The addition of the duodenal switch procedure to the BPD has reduced protein malabsorption from 11 to 3 percent [25]. (See "Overview of nutrient absorption and etiopathogenesis of malabsorption", section on 'Protein'.)

Long-term dietary recommendations include consuming small, nutrient-dense meals that are high in protein, along with fruits, vegetables, whole grains, and omega-3 fatty acids, and avoiding intake of concentrated sweets.

MACRONUTRIENT MANAGEMENT — Early postoperative diet stages are based upon meeting essential nutrient needs and maintaining adequate hydration. However, as weight stabilizes, patients will begin to obtain the bulk of their energy needs from dietary sources. By then, the calorie and macronutrient requirements of patients who have undergone a sleeve gastrectomy (SG) or a Roux-en-Y-gastric-bypass (RYGB) do not differ from those of the general population. (See "Obesity in adults: Dietary therapy" and "Healthy diet in adults".)

Patients losing and maintaining weight should base their macronutrient intake on their total caloric intake [15]:

Protein — Enhanced Recovery After Surgery (ERAS) guidelines recommend that patients consume 60 to 80 grams of protein per day [11]. Protein intake should constitute at least 10 percent of daily caloric intake but not more than 35 percent, according to recommendations from the Institute of Medicine. Protein needs in weight maintenance can also be calculated based on 0.8 to 1.2 grams/kg body weight per day, although exact needs are not clearly defined and may need to be individually assessed [10]. Protein needs during the active weight loss phase should be calculated as 1.2 grams/kg body weight for preservation of fat-free mass [26]. An average of 60 to 120 grams of protein is required daily in all patients to maintain lean body mass during weight loss and for the long term [9]. This is especially important in those treated with malabsorptive procedures to prevent protein malnutrition. Due to excess malabsorption that occurs with biliopancreatic diversion with duodenal switch (BPD/DS), a protein intake of 1.5 to 2.0 g of protein/kg body weight per day may be required, making the average protein requirement per day approximately 90 g/day after that procedure [10]. Since dietary protein has a satiation value, a protein source is recommended at each meal and snack; distribution of protein intake throughout the day can decrease the risk of reactive hypoglycemia as well.

Carbohydrates — Carbohydrates are the preferred fuel for the liver, brain, and muscle. In the absence of carbohydrates in the diet, protein can be used instead, but through longer, less efficient metabolic processes that can contribute to symptoms including headaches, brain fog, confusion, and extreme fatigue. Carbohydrates should constitute approximately 50 percent of total caloric intake. To meet that requirement, a minimum of 50 grams per day should be consumed early postoperatively, advancing to 130 grams per day as diet intake increases. Patients should be educated to consume complex carbohydrates from sources such as whole fruits, vegetables, and whole grains. Simple sugars should be limited to less than 10 percent of daily caloric intake. This can be difficult for most patients in the early diet stages, as protein intake leads to early satiety. It is recommended to avoid foods such as doughy breads, rice, or pasta for the first few months postoperatively as these foods can often lead to feelings of discomfort, feeling overly full, or nauseated.

Fat — Fat should constitute approximately 20 to 35 percent of the daily caloric intake. For a women on a 1600-kcal-per-day diet, for example, daily fat intake should be approximately 35 to 60 grams. The bulk of the fat intake should be unsaturated fat.

MICRONUTRIENT MANAGEMENT — Micronutrient deficiencies are quite prevalent in patients with obesity. While some patients have baseline deficiencies before bariatric surgery, others may develop new deficiencies following the surgery, even years after it has been performed [3,27].

Micronutrient deficiencies are a particular problem following malabsorptive or combination procedures because of inadequate intake of nutrients and alterations in the digestive anatomy due to the operative procedures bypassing portions of the stomach, duodenum, and/or proximal jejunum [28]. As examples, portions of the duodenum and the small bowel are excluded from the alimentary path with Roux-en-Y gastric bypass (RYGB) (figure 1) and biliopancreatic diversion with duodenal switch (BPD/DS) (figure 2) operations, thereby bypassing critical absorptive surfaces in the gastrointestinal tract for some fat- and water-soluble vitamins (eg, folate, vitamin B12, and vitamin D) and minerals (eg, iron, calcium) [29]. (See "Bariatric procedures for the management of severe obesity: Descriptions".)

The risk for developing nutritional deficiencies following a purely restrictive procedure, such as laparoscopic adjustable gastric band (LAGB), is lower compared with malabsorptive or combination procedures. However, the risk depends upon changes in the patient's diet and eating habits. Nutritional deficiencies may occur in these patients due to low nutrient intake, poor food choices, food intolerances, excessive vomiting, and limited portion sizes. As examples, excessive and/or persistent vomiting due to a tight or displaced band can cause an acute deficiency of thiamine (see 'Vitamin B1 (thiamine)' below), and the overall intake of dietary iron can be reduced due to decreased food volume, particularly with a reduction in meat intake. (See 'Iron' below.)

Presurgical screening — It is common for patients with obesity preparing for bariatric surgery to have at least one vitamin or mineral deficiency preoperatively [30]. Thus, the American Society for Metabolic and Bariatric Surgery (ASMBS) intergraded health nutritional guides for the surgical weight loss patient recommend routine baseline presurgical screening for levels of thiamine, vitamin B12, folate, iron, vitamin D and calcium, fat-soluble vitamins (A, E, K), zinc, and copper [9]. These screening laboratory tests can be performed as an integral part of the preoperative clinical nutrition evaluation by a registered dietitian. (See "Bariatric surgery for management of obesity: Indications and preoperative preparation", section on 'Nutritional assessment'.)

Postsurgical screening — ASMBS guidelines further recommend nutrient assessments every three to six months in the first year after bariatric surgery, and annually thereafter with laboratory tests [9,12]. During each follow-up visit, clinicians should perform a review of systems to help identify symptoms of micronutrient malnutrition. Some of these symptoms may be subtle, such as loss of night vision, memory issues, or impaired learning (table 4). The routine panel of laboratory tests is determined by individual programs. The results of 30 blood tests performed for close to 5000 patients followed for five years after gastric bypass can be a useful reference [31].

Micronutrient deficiency, supplementation, and repletion — The ASMBS recommends micronutrient supplementation for all patients after bariatric surgery. Patients who develop symptoms suggestive of a micronutrient deficiency, or who have a micronutrient deficiency identified by screening laboratory tests, should be given appropriate repletion. Symptoms of specific micronutrient deficiencies, requirements for routine supplementation according to bariatric procedures, and requirements for repletion in case of deficiency are presented below for each micronutrient (table 3) [9].

Fat-soluble vitamins — Fat-soluble vitamins include vitamins A, D, E, and K. The jejunum and ileum are the primary sites of absorption for this class of vitamins [32,33]. Deficiencies in fat-soluble vitamins are more likely to occur following RYGB [29] or BPD/DS [34-37]. Obesity is associated with vitamin D deficiency and secondary hyperparathyroidism, even in patients who have not undergone bariatric surgery [38-40]. Clinical syndromes associated with fat-soluble vitamins are given in the table (table 4).

The recommended daily allowance (RDA) for fat-soluble vitamins in the general population can be found in the included table (table 5). The supplementation of fat-soluble vitamins following RYGB and sleeve gastrectomy (SG) is shown in the included table (table 3). Supplementation with fat-soluble vitamin complexes is also advised after BPD/DS as the fat malabsorption caused by the operation leads to frequent deficiencies of these vitamins.

Vitamin A — A reported 14 percent of patients with obesity have vitamin A deficiency before bariatric surgery [41]. Eight to 11 percent of patients develop vitamin A deficiency after RYGB; 70 percent develop vitamin A deficiency within four years of BPD/DS [42,43]. Early symptoms of vitamin A deficiency include night blindness, Bitot's spots (picture 1), poor healing, hyperkeratinization of the skin, and loss of taste. Late symptoms can include corneal damage, xerosis, or even blindness. (See "Overview of vitamin A", section on 'Deficiency'.)

Patients should receive a vitamin A supplement of 5000 IU daily after LAGB, 5000 to 10,000 IU daily after RYGB or SG, and 10,000 IU daily after BPD/DS [35]. Laboratory screening is recommended in the first year postoperatively; if deficient, patients should receive additional supplements.

Patients with vitamin A deficiency but without corneal changes should receive 10,000 to 25,000 IU daily orally until clinical improvement (one to two weeks); those with corneal changes should be given 50,000 to 100,000 IU daily intramuscularly for three days, followed by 50,000 IU/day for two weeks [10].

Vitamin D — Vitamin D deficiency has been reported in 90 percent of patients before and 100 percent of patients after bariatric surgery [41]. Lack of vitamin D activity leads to reduced intestinal absorption of calcium and phosphorus. Early in vitamin D deficiency, hypophosphatemia is more marked than hypocalcemia. With persistent vitamin D deficiency, hypocalcemia occurs and causes secondary hyperparathyroidism, which leads to phosphaturia, demineralization of bones, and, when prolonged and severe, to osteomalacia in adults and rickets and osteomalacia in children. (See "Vitamin D deficiency in adults: Definition, clinical manifestations, and treatment", section on 'Clinical manifestations' and "Overview of vitamin D", section on 'Deficiency and resistance' and "Causes of vitamin D deficiency and resistance", section on 'Gastric bypass'.)

After bariatric surgery, patients should receive 3000 IU of D3 daily from all sources to maintain a 25(OH)D level of >30 ng/mL (75 nmol/L) [44] (see 'Postsurgical screening' above). However, the optimal level of 25(OH)D to prevent secondary hyperparathyroidism is uncertain. In one study of 171 patients who underwent an RYGB procedure two years earlier, parathyroid hormone (PTH) levels and the prevalence of secondary hyperparathyroidism were notably lower with 25(OH)D ≥40 ng/mL (100 nmol/L) compared with lower target levels [45].

Patients with vitamin D deficiency should receive 3000 to 6000 IU of D3 daily (preferred) or 50,000 IU of D2 one to three times per week [9]. Vitamin D deficiency must be corrected in order to achieve a normal calcium level. (See 'Calcium' below.)

Vitamin E — A reported 2.2 percent of patients have a vitamin E deficiency before bariatric surgery [41]. Vitamin E deficiency can cause neuromuscular disorders and hemolysis. Neuromuscular disorders associated with vitamin E deficiency are mostly of the neuropathic and myopathic type. Clinical manifestations include ataxia, hyporeflexia, and loss of proprioceptive and vibratory sensation. (See "Overview of vitamin E", section on 'Deficiency'.)

After bariatric surgery, adult patients and adolescents ages 14 and over should receive vitamin E supplements of 15 mg (22.4 IU) per day [35]. Breastfeeding women should receive 19 mg, or 28.4 IU, per day. (See 'Postsurgical screening' above.)

Patients with vitamin E deficiency should receive 100 to 400 IU daily (90 to 300 mg), although the optimal dose is not well established [10].

Vitamin K — Clinical signs and symptoms of vitamin K deficiency include easy bruisability, mucosal bleeding, splinter hemorrhages, melena, hematuria, or any other manifestations of impaired coagulation. (See "Overview of vitamin K", section on 'Vitamin K deficiency'.)

Patients should receive daily supplements of 90 to 120 mcg of vitamin K after LAGB, RYGB, or SG, or 300 mcg daily after BPD/DS [35]. (See 'Postsurgical screening' above.)

The treatment for vitamin K deficiency due to acute malabsorption is 10 mg of parenteral vitamin K. The treatment for those with chronic malabsorption is 1 to 2 mg per day orally or 1 to 2 mg per week parenterally [10].

Water-soluble vitamins — The water-soluble vitamins and deficiency syndromes can be found in the included table (table 4). Long-term deficiencies in water-soluble vitamins have been reported [46]. (See "Overview of water-soluble vitamins".)

Vitamin B1 (thiamine) — Vitamin B1 (thiamine) is absorbed through carrier-mediated active transport, primarily in the duodenum and proximal jejunum [47]. RYGB and BPD/DS patients are at a particularly elevated risk since their alimentary path bypasses the duodenum and proximal jejunum. Vitamin B1 deficiency may occur within three weeks after bariatric surgery in the patient with persistent vomiting or severely diminished oral intake [48,49]. Thiamine deficiency may be caused or exacerbated by alterations in gut flora following an RYGB [50].

Asymptomatic, abnormally low thiamine concentrations have been reported in 16 to 29 percent of preoperative patients [51,52] and in <1 to 49 percent of post-bariatric patients, depending on the type of surgery and length of follow-up [50,53]. The most common manifestation of vitamin B1 deficiency in the post-bariatric bypass surgical population is Wernicke encephalopathy (WE), a neurologic condition causing encephalopathy, oculomotor dysfunction, and gait ataxia [54].

Because neurologic deficits related to thiamine deficiency can become permanent if untreated, any bariatric patient who presents with prolonged vomiting should have a neurologic examination and be given thiamine until it can be proven that the patient does not have a thiamine deficiency. A laboratory test for thiamine level obtained at the initial encounter may take a few days to come back. Patients with suspected WE should not be administered intravenous solutions containing glucose, as these may deplete the remaining available thiamine and precipitate Korsakoff's syndrome, a chronic neurologic condition that usually occurs as a consequence of WE. (See "Wernicke encephalopathy".)

To prevent vitamin B1 deficiency, post-bariatric surgery patients should receive at least 12 mg of thiamine daily. Since over-the-counter multivitamins typically contain less than that amount, it is preferable for patients to take a B-complex supplement containing 50 mg of thiamine one or twice daily, in addition to a multivitamin [9,55].

Management of vitamin B1 deficiency includes:

●Administer thiamine in one of the following three regimens:

•Oral: 100 mg two to three times daily until symptoms resolve.

•Intravenous: 200 mg three times daily to 500 mg once or twice daily for three to five days, followed by 250 mg daily for three to five days, and subsequent oral maintenance (100 mg daily) indefinitely [9,56].

•Intramuscular: 250 mg daily for three to five days [57,58] or 100 to 250 mg monthly [9,59,60].

●Simultaneously replete magnesium, potassium, and phosphorus to prevent refeeding syndrome.

●Immediate treatment of surgical causes of vomiting (eg, obstruction).

Vitamin B12 — The prevalence of preoperative vitamin B12 deficiency has been reported to range from 0 to 18 percent [51]. Bariatric procedures, including RYGB and SG, can result in vitamin B12 deficiency. Vitamin B12 deficiency is relatively common after RYGB, occurring in one-third or more of postoperative patients [61-64]. There are relatively few parietal cells present in the small gastric pouch; therefore, inadequate gastric acid is available for the initial step, the cleavage of vitamin B12 from dietary protein [65]. Additionally, a decreased amount of intrinsic factor may be available after RYGB [66]. Patients who have undergone an RYGB are at a greater risk for vitamin B12 deficiency compared with patients managed with an SG (42 versus 5 percent) [67]. The prevalence of B12 deficiency after SG ranges from 4 to 20 percent [68-71].

Vitamin B12 deficiency, which results in pernicious (megaloblastic) anemia, is permanent, and lifelong management is warranted with oral or parenteral supplements [29]. (See "Treatment of vitamin B12 and folate deficiencies", section on 'Vitamin B12' and "Causes and pathophysiology of vitamin B12 and folate deficiencies", section on 'Causes of vitamin B12 deficiency'.)

We advise a daily oral dose of vitamin B12 of 350 to 1000 mcg for postoperative bariatric surgery management [9]. Alternatively, patients can be treated with 1000 mcg of B12 intramuscularly or subcutaneously (monthly), or by nasal spray preparations (dose per manufacturer) [9]. Peripheral neuropathy resulting from chronic vitamin B12 deficiency may not be reversible and must be prevented by diligent laboratory monitoring and adequate replacement. Since the body has a 12 to 18 month storage of vitamin B12, B12 deficiency is identified approximately two years or more following surgery; therefore, yearly long-term laboratory monitoring is essential. (See 'Postsurgical screening' above.)

Patients with B12 deficiency should receive 1000 mcg of B12 daily until the level is normalized before resuming maintenance doses [72,73].

Folate — Folate deficiency, which also induces megaloblastic anemia, is less common than vitamin B12 deficiency since folic acid is absorbed throughout the entire small intestine. The preoperative prevalence of folate deficiency in patients with obesity is 0 to 54 percent [74]. However, because folate is water soluble and there are no long-term stores in the body, deficiencies may arise due to inadequate oral intake. Malabsorption of folate is less common following RYGB and SG since the non-bypassed small bowel is usually adequate to absorb dietary folate [75,76]; deficiency is more common following BPD due to limited absorption. (See "Clinical manifestations and diagnosis of vitamin B12 and folate deficiency" and "Causes and pathophysiology of vitamin B12 and folate deficiencies".)

Supplementation is typically provided as a daily oral dose of 400 to 800 mcg, usually as a part of a multivitamin [77]. Women of childbearing age should take 800 to 1000 mcg daily [78]. Prenatal vitamins, which generally contain 1 mg of folate per tablet, can also be used [79].

Patients with folate deficiency should receive an oral dose of 1000 mcg daily until the level is normalized before maintenance doses can be resumed [9]. Folate supplementation above 1 mg per day is not recommended, due to the potential masking of vitamin B12 deficiency [80].

Vitamin C — Vitamin C (ascorbic acid) deficiency, which leads to scurvy, is uncommon following bariatric bypass procedures, as long as the patient consumes fruits and vegetables. (See "Overview of water-soluble vitamins", section on 'Vitamin C (ascorbic acid)'.)

Supplementation of vitamin C may enhance absorption of iron from both dietary sources, and supplements should be considered in patients who do not respond to oral iron therapy [81].

Trace minerals — Minerals form only 5 percent of the typical human diet but are essential for normal health and function. Macrominerals are defined as minerals that are required by adults in amounts greater than 100 mg/day or that make up less than 1 percent of total body weight. Trace elements (or trace minerals) are usually defined as minerals that are required in amounts between 1 to 100 mg/day by adults or make up less than 0.01 percent of total body weight. Ultra-trace minerals generally are defined as minerals that are required in amounts less than 1 mg/day. Although the classification of mineral may be controversial and somewhat arbitrary, one outline is given in the table (table 6). (See "Overview of dietary trace elements".)

Iron — Iron deficiency is one of the most common nutritional problems following bariatric surgery and results in hypochromic and microcytic anemia. Iron is primarily absorbed in the duodenum and proximal jejunum; bariatric bypass operations, namely RYGB and BPD/DS, exacerbate this problem. In addition, dietary iron is commonly bound to protein and cleaved by the action of gastric acid in the stomach. Because there is only a small amount of gastric-acid-producing tissue in the RYGB pouch or SG remnant, iron absorption may be further reduced [65,82-85]. (See "Causes and diagnosis of iron deficiency and iron deficiency anemia in adults", section on 'Causes and risk factors for iron deficiency' and "Overview of dietary trace elements", section on 'Deficiency'.)

Iron deficiency is identified in 0 to 58 percent of patients with obesity preoperatively and 8 to 50 percent of postoperative bariatric patients, particularly in women who are still menstruating [9]. In a retrospective review of 164 patients who underwent RYGB, 42.3 percent of women and 22.0 percent of men developed iron deficiency (serum ferritin concentration ≤20 mcg/L) [86].

After bariatric surgery, males and patients without history of anemia should receive at least 18 mg of iron from a multivitamin. Menstruating females and those who have undergone RYGB, SG, or BPD/DS should take at least 45 to 60 mg of elemental iron daily [9]. Most multivitamins do not have enough iron in the elemental form to achieve this level of supplementation. Taking vitamin C with iron increases absorption; calcium supplements and foods containing high amounts of calcium will decrease absorption.

Management of iron deficiency depends upon the acuity of the illness and includes oral and parenteral administration of elemental iron. Many programs treat post-bariatric surgery patients with iron deficiency with 150 to 300 mg of iron orally two to three times daily [9]. However, in a randomized controlled trial comparing oral and intravenous iron supplementation in 120 women with serum ferritin <20 mcg/L, oral supplements for three months failed to normalize ferritin levels in 29 percent of patients receiving ferrous fumarate and 42 percent of those receiving ferrous gluconate, whereas all patients treated with intravenous ferric carboxymaltose normalized ferritin levels at three months after intravenous infusion [87]. A systematic review of 49 studies with 12,880 patients who underwent bariatric surgery concluded that oral iron supplementation is not a sufficient strategy to prevent the development of iron deficiency and iron deficiency anemia and that intravenous supplementation is more effective in treating iron deficiency [88].

The treatment for iron deficiency anemia is reviewed in detail separately. (See "Treatment of iron deficiency anemia in adults".)

Zinc — Zinc, like other divalent cations, is absorbed in the duodenum and proximal jejunum and linked to fat absorption. Zinc deficiency results in growth retardation, delayed sexual maturity, impotence, and impaired immune function, among other medical conditions. (See "Overview of dietary trace elements", section on 'Zinc'.)

The prevalence of zinc deficiency ranges from 9 to 74 percent in patients seeking BPD/DS [89-91]. Zinc deficiency can follow bypass or malabsorptive bariatric operations [92,93]. A retrospective review of 73 patients undergoing a BPD without duodenal switch and 61 patients undergoing a BPD/DS found that 11 percent of all patients developed zinc deficiency two to three years after surgery [94]. There was no difference between the patients undergoing a BPD versus a BPD/DS. Zinc deficiency occurs in approximately 6 to 40 percent of patients after RYGB [4,5,30,92].

Post-bariatric surgery patients should receive zinc supplementation according to the type of procedure [9]:

●BPD/DS: Multivitamin containing 200 percent of RDA for zinc (16 to 22 mg daily)

●RYGB: Multivitamin containing 100 to 200 percent of RDA for zinc (8 to 22 mg daily)

●LAGB: Multivitamin containing 100 percent of RDA for zinc (8 to 11 mg daily)

A ratio of 1 mg copper supplementation has been recommended for every 8 to 15 mg of elemental zinc to prevent copper deficiency [9]. (See 'Copper' below.)

Management of a zinc deficiency is by oral administration of 60 mg of zinc twice daily [9]. The current optimal dose is unknown [95]. Megadoses are associated with toxicity, including copper deficiency and gastrointestinal symptoms [9]. (See "Overview of dietary trace elements", section on 'Toxicity'.)

Copper — Copper is absorbed in the stomach and proximal duodenum [96,97]. It is required for red and white blood cell production and for normal functioning of the nervous system [98]. Copper deficiency results in microcytic anemia, neutropenia, and ataxia and is worsened by iron supplements. (See "Overview of dietary trace elements", section on 'Copper'.)

An acquired copper deficiency has been reported following bypass bariatric operations, such as RYGB and BPD/DS operations [99]. In a retrospective review of records of 136 patients who had undergone RYGB, 13 (10 percent) were found to have copper deficiency; a separate analysis from the same study followed 16 patients prospectively for two years, and three developed copper deficiency [100]. The clinical presentation is often indistinguishable from subacute combined degeneration, a condition found in patients with vitamin B12 deficiency [101]. (See "Copper deficiency myeloneuropathy", section on 'Clinical manifestations'.)

Post-bariatric surgery patients should receive copper supplementation according to the type of procedure:

●BPD/DS or RYGB: Multivitamin containing 200 percent of RDA for copper (2 mg daily)

●SG or LAGB: Multivitamin containing 100 percent of RDA for copper (1 mg daily)

A ratio of 1 mg copper supplementation has been recommended for every 8 to 15 mg of elemental zinc to prevent copper deficiency [9].

Management of copper deficiency depends on the severity of the deficiency [9,10]:

●Mild-to-moderate deficiency (low hematologic indices): 3 to 8 mg copper orally until levels normalize

●Severe deficiency (neurologic symptoms): 2 to 4 mg copper intravenously for six days or until symptoms resolve

Hematologic abnormalities may respond with two months of therapy, while neurologic symptoms may persist long term. (See "Copper deficiency myeloneuropathy", section on 'Treatment' and "Sideroblastic anemias: Diagnosis and management", section on 'Copper deficiency'.)

Selenium — Selenium is absorbed in the duodenum and proximal jejunum by the methionine pathway [98]. Selenium deficiency results in skeletal muscle dysfunction and cardiomyopathy and has been implicated in mood disorders, impaired immune function, and macrocytosis. (See "Overview of dietary trace elements", section on 'Selenium'.)

Selenium deficiency has been reported in 14 to 22 percent of patients following an RYGB and BPD/DS procedure, respectively [94,102]. The optimal range for dietary intake of selenium is narrow; potentially toxic intakes are closer to recommended dietary intakes than for other dietary trace minerals. Management includes oral supplementation with an estimated goal of over 100 mcg/day [103]. In a few studies, the use of 2 mcg/kg/day was used for repletion when patients suffered cardiomyopathy from selenium depletion [104].

Calcium — After bypass bariatric surgery, dietary intake of both calcium and vitamin D may be reduced. Dietary calcium is best absorbed in the duodenum and proximal jejunum, where the highest concentration of calcium transporters is present. Calcium is passively absorbed through the entire gastrointestinal tract. Additionally, calcium is better absorbed in an acidic environment; since gastric acid exposure is reduced in RYGB, SG, and BPD/DS, these patients are at an increased risk of calcium malabsorption. In one study, 3.6 percent of patients developed hypocalcemia after bariatric surgery, including 1.9 percent after RYGB, 9.3 percent after SG, and 10 percent after BPD/DS [105]. (See "Etiology of hypocalcemia in adults".)

The absorption of calcium is dependent upon vitamin D, which is absorbed in the jejunum and ileum and bypassed by bariatric operations such as RYGB and BPD/DS [106]. BPD/DS patients are additionally at risk for vitamin D deficiency due to their fat malabsorption [33]. The plasma level of vitamin D has been shown to decline over time after bariatric surgery [107]. (See 'Vitamin D' above.)

Calcium deficiency is associated with metabolic bone disease and secondary hyperparathyroidism. Management of hypocalcemia depends upon the severity of disease and includes oral and parenteral administration of calcium and vitamin D. (See "Treatment of hypocalcemia", section on 'Therapeutic approach' and "Treatment of hypocalcemia", section on 'Vitamin D deficiency'.)

Secondary hyperparathyroidism can develop or persist postoperatively [108-110]. Affected patients will show elevated levels of parathyroid hormone and normal-to-low serum calcium [110]. A systematic review of 14 studies (n = 2688 patients) showed that secondary hyperparathyroidism persists at five years following RYGB [111]. One study in 193 women in the United States found that postmenopausal women, African American women, and those with a higher body mass index (BMI) were at increased risk of developing secondary hyperparathyroidism after RYGB [110].

The clinical significance of prolonged hyperparathyroidism in the bariatric surgery patient is unknown. This is a relatively controversial issue. While PTH is commonly noted to be elevated in bariatric patients, it is not clear if it represents bone loss or increased turnover. There are no good data to support aggressive treatment of elevated PTH in the presence of adequate vitamin D levels.

For patients who have undergone RYGB, SG, BPD/DS, and LAGB, the ASMBS suggests [112]:

●Routine supplementation of calcium and vitamin D, as discussed elsewhere in this topic.

●Monitor bone loss with albumin, calcium, PTH, and 25(OH)D levels annually.

●Markers for altered bone turnover (eg, alkaline phosphatase, osteocalcin) have not been established as appropriate screening tools.

●Routine DXA scan after bariatric surgery beyond a baseline examination is not supported by data.

Post-bariatric surgery patients should receive calcium supplementation according to the type of procedure [44]:

●BPD/DS: 1800 to 2400 mg daily

●RYGB, SG, or LAGB: 1200 to 1500 mg daily

The recommended doses of calcium repletion are identical to the doses of calcium supplementation described above. In order to enhance absorption, calcium supplements should be given in divided doses, with meals for calcium carbonate and with or without meals for calcium citrate. Calcium carbonate, while more widely available, is not as well absorbed after RYGB, due to decreased acidity of the gastric pouch. Calcium citrate is better absorbed in an achlorhydric environment such as the post-RYGB stomach pouch; however, calcium carbonate is less expensive and more readily available and may be recommended in patients after an SG given that more gastric acid-producing cells are preserved. Cost, availability, and patient compliance should all be taken into consideration when making supplementation recommendations [113].

The supplementation of vitamin D is discussed in a separate section. (See 'Vitamin D' above.)

EATING DISORDERS — A significant number of individuals go into obesity surgery with preexisting disordered eating behavior, such as binge eating disorder or food addictions [114]. Patients with disordered eating are unlikely to disclose these behaviors to their clinician unless they are solicited. Asking patients to describe what they ate during the past 24 hours in a nonjudgmental and nonthreatening manner can often identify dysfunctional eating patterns. (See "Dietary assessment in adults" and "Eating disorders: Overview of epidemiology, clinical features, and diagnosis".)

In order to maintain the weight loss that typically follows surgery, patients must significantly change their eating patterns. General normalization of eating behavior has been reported, characterized by fewer meals, less food consumed at each meal, less eating between meals, and less eating in response to strong emotions [6,115,116]. Severe binge eating becomes virtually impossible following Roux-en-Y gastric bypass (RYGB) due to the severely restricted stomach.

Despite this, patients with a preoperative history of eating disorders are more likely to have difficulty adjusting to the change in eating habits, and some may continue to have disordered eating patterns. Referral to an experienced psychologist can help unmask some of the underlying emotional issues associated with food.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Bariatric surgery".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Care after weight loss surgery (The Basics)")

●Beyond the Basics topic (see "Patient education: Losing weight (Beyond the Basics)").

SUMMARY AND RECOMMENDATIONS

●Diet advancement after bariatric surgery – The early diet advancement after bariatric surgery is based upon a staged approach with emphasis on nutritional needs at each stage of healing and weight loss (table 1 and table 2) (see 'Early (postoperative) diet' above):

•Postoperative weeks 1 and 2: Hydration and liquids.

•Postoperative week 3 and beyond: Solid foods, advancing food texture and amounts as tolerated.

•Once maintenance weight is achieved: Healthy, balanced diet and micronutrient supplements.

•Long-term eating habits are in part determined by the patient's motivation, willingness, and ability to adhere to a healthy diet. Dietary intake longer term is also dependent upon the type of bariatric procedure performed. (See 'Long-term diet and habit changes' above.)

●Macronutrient management – Early after bariatric surgery, patients use stored adipose tissue for energy needs. Thus, early postoperative diet stages are based upon meeting essential nutrient needs and maintaining adequate hydration. As weight stabilizes and patients are obtaining the bulk of their energy needs from dietary sources, the nutritional recommendations for macronutrients do not differ from those of the general population. (See 'Macronutrient management' above.)

●Micronutrient management

•Presurgical screening – It is common for patients with obesity preparing for bariatric surgery to have at least one vitamin or mineral deficiency preoperatively. Thus, patients should undergo routine baseline presurgical screening for levels of thiamine, vitamin B12, folate, iron, vitamin D and calcium, fat-soluble vitamins (A, E, K), zinc, and copper. (See 'Presurgical screening' above.)

•Postsurgical screening – After bariatric surgery, patients should undergo nutrient assessments every three to six months in the first year, and annually thereafter. Routine laboratory tests are determined by individual programs. (See 'Postsurgical screening' above.)

•Micronutrient supplementation – To prevent micronutrient deficiency, patients should receive daily vitamin and mineral supplementation determined by the bariatric procedure after bariatric surgery (table 3). (See 'Micronutrient management' above.)

•Micronutrient repletion – Patients with symptoms suggestive or a laboratory test diagnostic of a micronutrient deficiency should receive repletion of that micronutrient (table 3). (See 'Micronutrient management' above.)

ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge Susan Cummings, MS, RD, who contributed to an earlier version of this topic review.