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Nutritional Support after Bariatric Surgery
Sebastio Perrini
Bariatric surgery provides substantial and sustained effects on weight loss and ameliorates obesity-
attributable comorbidities in the majority of bariatric patients, although risks of complication,
reoperation, and death exist (1). While a patient’s surgeon monitors closely for postoperative
surgical complications, the primary care provider or endocrinologist is often the provider to identify
and manage postoperative medical and nutritional complications. This chapter reviews these
potential nutritional complications with attention to screening, and therapeutic approach.
Early and Late Nutritional Management
Most bariatric procedures include the reduction of the volume of the stomach and/or the
creation of a small gastric pouch. Therefore, the ingestion of solid foods in the first days after
surgery is impossible and a gradual change of food consistency in the first post-operative
weeks is preferred in order to avoid or minimise regurgitation and vomiting, which can
threaten the integrity and safety of the recent surgical procedure, and result in severe vitamin
B1 (thiamine) deficiency (2). After bariatric surgery, a low-sugar clear liquid meal programme is
usually initiated within 24 h, and patients are then informed to gradually and progressively change
the food consistency, moving from clear liquids to soft or creamy foods and then to solid chewable
items over a period of 2-4 weeks (2,3). The aim of dietary counselling should be the fitting of
patients’ eating behaviour to the surgical procedure and the general qualitative aspects of a healthy
nutrientdense diet. In detail, patients with gastric restriction should be counselled to eat three
small meals during the day and chew small bites of food thoroughly befo re swallowing,
without drinking beverages at the same time (more than 30 min apart) (2,3). Regular physical
activity is considered a critical factor for weight maintenance and should therefore be encouraged
after bariatric surgery. Patients should be advised to carry out moderate aerobic physical activity,
i.e., a minimum of 150 min/week (with a goal of 300 min/week) as well as strength training 2–3
times/week (2-3).
Protein Supplementation
Protein intake is generally reduced following bariatric surgery and then adequate protein intake is
prominent to counteract the loss of lean body mass in any situation when a rapid weight loss occurs
(4). Dietary counselling should address the problem of protein intake, particularly in the first
months after surgery. Current guidelines suggest a minimal protein intake of 60 g/day and up to 1.5
g/kg ideal body weight per day, but higher amounts of protein intake (up to 2.1 g/kg ideal body
weight per day) may be required in individual cases (2-6). The use of liquid protein supplements
(30 g/day) can facilitate adequate protein intake in the first period after surgery. Bariatric
procedures involving a certain degree of malabsorption can cause protein malnutrition. The
incidence of protein malnutrition depends on the degree of the malabsorption as well as on the
dietary habits and the protein requirements of the patients. A 13% incidence has been reported after
distal Roux-en Y gastric bypass (RYGB) with a Roux limb ≥ 150 cm, whereas an incidence of
protein malnutrition ranging from 3 to 18% has been reported after biliopancreatic diversion (3).
Prevention of protein malnutrition involves regular rating of protein intake, fostering the ingestion
of protein-rich foods (>60 g/day) divided into several meals and the use of modular protein
supplements (2,3). In case of severe non-responsive protein malnutrition parenteral nutrition is
recommended, and surgical revision with lengthening of the common channel to decrease
malabsorption should be considered if a patient remains dependent on parenteral nutrition or has
recurrent episodes of protein depletion (2-4) .
Micronutrient Deficiencies
Given the dietary changes, rerouting of nutrient flow, and gut anatomy/physiology alterations that
occur after bariatric surgery, patients who undergo these procedures are at risk for micronutrient
deficiencies. Some of these deficiencies can result in severe consequences, such as neuropathy,
heart failure, and encephalopathy. Therefore, it is extremely important that patients understand the
need for lifelong supplementation. Patients who have malabsorptive procedures, such as Roux-en-Y
Gastric Bypass (RYGB) or BilioPancreatic Diversion with Duodenal Switch (BPD/DS), are at
highest risk for micronutrient deficiencies and require a more extensive preoperative nutritional
evaluation and postoperative monitoring and supplementation. But even with restrictive procedures,
decreased oral intake and poor tolerance to certain food groups may also increase the risk for
micronutrient deficiencies (2-5).
Tables 1-3 represent recommendations that have been adapted from the American Society for
Metabolic and Bariatric Surgery (ASMBS) Integrated Health Nutrition Guidelines (6), Clinical
Practice Guidelines from the combined American Association of Clinical Endocrinologists
(AACE), The Obesity Society (TOS), and ASMBS (7), and The Endocrine Society Clinical Practice
Guidelines (8). These recommendations for adults reflect general guidelines, and patients with
specific diseases may require further evaluation and closer monitoring. For example, in
malabsorptive bariatric surgical procedures the resulting nutritional anemias beyond that an
appropriate iron repletion might also require other micronutrient deficiencies in vitamin B12, folate,
protein, copper, selenium and zinc, and these should be evaluated.
Preexisting micronutrient deficiencies would be corrected prior to surgery in order to avoid
clinically symptomatic or severe disease. For example, suboptimal levels of 25-hydroxyvitamin D
are particularly common and may require supplementation prior to surgery.
Is universally accepted that post-bariatric supplementation (Table 1) is an important component of
postoperative care. For example, vitamin B12 deficiency is common after RYGB without adequate
supplementation, and oral doses of 350 mcg/day have been shown to maintain normal plasma B12
levels. Other suggested micronutrient doses are either based on expert opinion or are similar to the
recommended dietary allowance (RDA) (6-8).
Table 1. Recommended postoperative supplementation of vitamins and minerals
Micronutrient
Supplementation
Within a multivitamin with minerals product
Thiamine
12 mg/day
Vitamin B12 (cobalamin)
Oral or sublingual: 350-500 mcg/day
Intranasal: 1000 mcg/week*
Intramuscular: 1000 mcg/month
Folate (folic acid)
400-800 mcg/day
Women of childbearing age: 800-1000 mcg/day
Iron
18 mg/day elemental iron
RYGB, SG, BPD/DS or menstruating women: 45-60 mg/day
Take separately from calcium supplements
Vitamin D
D3 3000 IU/day
Vitamin A
LAGB: vitamin A 5000 IU/day
RYGB or SG: vitamin A 5,000-10,000 IU/day
BPD/DS: vitamin A 10,000 IU/day
Vitamin E
15 mg/day
Vitamin K
LAGB, SG or RYGB: 90-120 mcg/day
BPD/DS: 300 mcg/day
Zinc
SG or LAGB: 8-11 mg/day
RYGB: 8-22 mg/day
BPD/DS: 16-22 mg/day
Copper
SG or LAGB: 1 mg/day
RYGB or BPD/DS: 2 mg/day
As separate supplementation
Calcium
LAGB, SG, RYGB: calcium 1200-1500 mg/day (diet + supplements)
BPD/DS: calcium 1800-2400 mg/day (diet + supplements)
(as calcium citrate, in divided doses)
Most micronutrients are provided in multivitamins, and chewable multivitamins are recommended
postoperatively. Multivitamins for the general population can be used, provided that attention is
paid to the product’s micronutrient contents. The ASMBS recommends one general multivitamin
tablet daily for patients who have had Laparoscopic Adjustable Gastric Banding (LAGB), or 2
general multivitamin tablets daily for those undergoing Sleeve Gastrectomy (SG), RYGB or
BPD/DS. As an alternative to general multivitamins, bariatric surgery-specific, high-potency
multivitamins are available and often contain the recommended doses of micronutrients in one
tablet daily (6).
Multivitamins do not contain the recommended doses of calcium, as calcium can impede the
absorption of other micronutrients. Therefore, separate calcium supplementation is usually required.
Calcium citrate is the preferred form of supplemental calcium, as it is better absorbed than calcium
carbonate in the state of impaired gastric acid production. A patient’s dietary calcium intake should
be considered when determining the dose of a calcium supplement, as the recommended intakes are
generally total daily intakes (diet plus supplements) (6). Iron absorption may be enhanced by co-
administration of vitamin C (500-1000 mg) to create an acidic environment or when taken with
meat. If inadequate absorption or intolerance occurs, parenteral iron replacement may be necessary.
A suggested schedule for postoperative biochemical monitoring is listed in Table 2. Patients who
develop micronutrient deficiencies may need more frequent monitoring.
Examinations should be performed after RYGB or BPD/DS. All of these could be suggested for
patients submitted to restrictive surgery where frank deficiencies are less common.
Some surgeons perform additional early biochemical evaluation 3 months postoperatively, and the
AACE/TOS/ASMBS Clinical Practice Guidelines suggest evaluation earlier than 6 months for
some micronutrients (7).
Table 2. Schedule for postoperative micronutrient monitoring
6 months
12 months
18 months
24 months
Annually
Vitamin B12
X
X
X
X
X
Folate
X
X
X
X
X
Iron, ferritin
X
X
X
X
X
25-hydroxyvitamin D
X
X
X
X
X
Calcium
X
X
X
X
X
Intact PTH
X
X
X
X
X
24-hour urinary calcium
X
X
X
X
Thiamine
Optional
Optional
Optional
Optional
Optional
Vitamin A
Optional
Optional
Zinc
Optional
Optional
Optional
Optional
Copper
Optional
Optional
Oral repletion is often sufficient for correcting micronutrient deficiencies, although parenteral
therapy may be required in severe disease. After a repletion course, biochemical testing should be
performed and a maintenance dose should be established. Micronutrient deficiencies may co-exist;
for example, malabsorptive procedures may result in deficiencies of the fat-soluble vitamins A, E
and K (6-8).
Table 3. Repletion recommendations for micronutrient deficiencies
Micronutrient
Repletion recommendation
Thiamine
Oral: 100 mg 2-3 times daily
IM: 250 mg daily for 3-5 days or 100-250 mg monthly
IV: 200 mg 2-3 times daily to 500 mg 1-2 times daily for 3-5 days, followed
by 250 mg/day for 3-5 days
Severe disease: administer thiamine prior to dextrose-containing solutions
Vitamin
B12(cobalamin)
Oral: 1000 mcg/day
IM: 1000 mcg/month to 1000-3000 mcg/6-12 months
Folate (folic acid)
1000 mcg/day orally
Iron
150-200 mg elemental iron/day, up to 300 mg 2-3 times daily
Calcium may impair iron absorption
Consider co-administration of vitamin C to enhance absorption
Consider IV iron infusions for severe/refractory iron deficiency
Vitamin D
D3 6000 IU/day or D2 50,000 IU 1-3 times per week, or more if needed to
achieve and maintain 25-hydroxyvitamin D >30 ng/mL
Calcium
Increase dose and titrate to normalize PTH ± 24-hr urinary calcium level
Vitamin A
10,000-25,000 IU/day orally until clinical improvement (1-2 weeks)
With corneal changes: 50,000-100,000 IU IM x 3 days, then 50,000 IU/day
IM for 2 weeks
Vitamin E
Optimal therapeutic dose not clearly defined, consider 100-400 IU/day
Vitamin K
Acute malabsorption: 10 mg parentally
Chronic malabsorption: 1-2 mg/day orally or 1-2 mg/week parentally
Zinc
There is insufficient evidence to make a dose-related recommendation
Copper
Mild-moderate deficiency: oral copper gluconate or sulfate 3-8 mg/day
Severe deficiency: 2-4 mg/day of intravenous copper x 6 days
IM, intramuscular; IV, intravenous
Dumping Syndrome
Dumping syndrome was believed to be typical of gastric bypass (70–75% of patients in the first
year after surgery) (7) , but it has been described also after sleeve gastrectomy (40% of patients 6
months after surgery) (15) . Early dumping syndrome typically occurs within 1 hour of eating and is
characterized by both gastrointestinal (nausea, abdominal fullness, diarrhea) and vasomotor
symptoms (fainting, sleepiness, weakness, diaphoresis, palpitations, and desire to lie down) (10).
Dumping syndrome symptoms can appear as early as 6 weeks after surgery and has been reported to
affect up to 20% according to large survey studies and up to 40% in smaller prospective studies of
individuals who have undergone both restrictive and malabsorptive procedures (11-14). The
pathophysiology of dumping syndrome is not completely understood but is thought to be due to
both a rapid delivery of nutrients to the small intestine causing an osmotic shift of intravascular
fluid to the intestinal lumen as well as an increased release of gastrointestinal hormones that disrupt
motility and hemodynamic status (15). There is debate in the literature on whether dumping
syndrome is an adaptive consequence of bariatric surgery that helps restrict food intake and aids
weight loss versus an adverse consequence that reduces quality of life and does not contribute to
weight loss (11).
The diagnosis of dumping syndrome should be made after the exclusion of more serious entities
such as intestinal fistulas, adhesions, ischemia, herniation, obstipation and gallstone disease which
may have shared clinical features (15). There are validated questionnaires as well as provocation
tests that have been used to confirm dumping syndrome in research settings. Oral glucose challenge
with an increase in heart rate and hematocrit (indicating hemoconcentration) is one such approach
(10).
The first line treatment for dumping syndrome is to modify the diet so as to avoid foods that worsen
symptoms (oftentimes calorie-dense foods with high fat/refined sugar content and low in fiber),
eating small volume meals, not eating and drinking at the same time, eating slowly, chewing well,
and avoiding alcohol. Indeed, patients often implement these changes on their own and, over time,
symptom severity improves or resolves in many (if not most) patients. In addition, lying down for
30 minutes after eating to slow gastric emptying and mitigate symptoms of hypovolemia may be
helpful if symptoms occur (15). There are several small interventional studies and case reports that
support the use of dietary supplements (e.g., pectin, guar gum) that increase food viscosity and
reduced symptoms of dumping syndrome, however low palatability and potential choking hazard
and bowel obstruction are downsides to their use (15). Somatostatin analogs have also been tested
in small studies, although this class of drugs are expensive, involve subcutaneous or intramuscular
injections, and have gastrointestinal side effects (15). Enteral tube feedings or bariatric surgery
reversal have been reported to improve symptoms when all else fails (15).
Conclusions
The postoperative management of the bariatric surgery patient requires a special knowledge and
skills of the clinicians in order to deliver appropriate and effective care to the post-bariatric patient.
Thus, an interdisciplinary team, including the surgeon, dietitian, and endocrinologist and/or primary
care provider should provide a follow-up program as an integral part of the clinical pathway at
centres delivering bariatric surgery. This follow-up program should be include the management of
chronic metabolic conditions and the prevention and treatment of postoperative medical and
nutritional complications to optimize the long-term benefits of bariatric surgery.
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