Am J C/ui Nutr 1996;63:103-9. Printed in USA. 10 1996 American Society for Clinical Nutrition 103

Vitamin B-12 deficiency after gastric surgery for obesity13

Barbara M Rhode, Paul Arseneau, Bernard A Cooper, Max Katz, Brian M Gilfix, and

Lloyd D MacLean

ABSTRACT Low serum vitamin B-12 concentrations after

gastric bypass (GB) surgery for obesity were observed in I 1 of 28

patients without detectable impairment of crystalline vitamin B- 12

absorption. This was observed in 2 of 19 patients with vertical

banded gastroplasty (VBG). In contrast, protein-bound vitamin

B-l2 absorption was markedly impaired, as demonstrated in eight

of these patients after GB (n = 7) and VBG (n = 1). Correction of

this impaired absorption occurred when protein-bound vitamin

B- 12 was incubated with an enzyme mixture before consumption.

Simultaneous ingestion of the enzyme mixture with protein-bound

vitamin B-l2 did not improve absorption of the vitamin. In a

separate experiment, 10 patients with a normal result from the

Schilling test failed to correct low serum vitamin B-12 concentra-

tions with a quantity of oral crystalline vitamin B-l2 equal to the

recommended dietary allowance of 2 �g, taken twice daily for 3

mo. Serum total homocysteine values declined during this interval.

An oral daily dose of 350 p�g crystalline vitamin B-l2 raised the

average serum vitamin B- I 2 concentration to an amount greater

than the lower reference limit. A dose > 350 �tg/d was required to

raise all patients’ vitamin B-l2 concentrations above this concen-

tration rather than just above the population mean. We conclude

that because concentrations of oral crystalline vitamin B- 12 were

required to normalize serum vitamin B- I 2 concentrations, that a

mechanism other than formation of a vitamin B- 12 intrinsic factor

complex is responsible for crystalline vitamin B-l2 absorption

after GB for obesity. A�ii J C/in Nutr 1996:63:103-9.

KEY WORDS Vitamin B-l2, absorption, Schilling test,

intrinsic factor, severe obesity, gastric bypass, gastroplasty,

dietary requirements

INTRODUCTION

Dietary deficiency of vitamin B- 1 2 is rare because of its

widespread distribution in animal foods and its extensive stor-

age in the liver. Nutritional vitamin B-12 deficiency has been

found only in strict vegetarians who avoid meat, eggs, and

milk. Because such dietary deficiency is unusual, it follows that

deficiency of vitamin B- I 2 is usually the result of defective

absorption.

The normal sequence of events leading to absorption of

protein-bound vitamin B- I 2 begins with the release of vitamin

B-l 2 from protein sources by the digestive action of hydro-

chloric acid and pepsin in the stomach. The freed vitamin B-12

attaches to R-binder proteins from the saliva and gastric juice,

and in turn is released from these by pancreatic enzymes in the

upper small intestine. The vitamin B-l2 molecule is then

rapidly transferred to intrinsic factor to form a complex that is

resistant to tryptic proteolysis. The vitamin B- 1 2 intrinsic fac-

tor complex usually remains intact until it adheres to specific

receptors in the distal ileum in anticipation of absorption ( 1).

Vitamin B-I 2 deficiency after total or near total gastrectomy

develops from 3 to 6 y after the procedure, and results from a

lack of intrinsic factor. Megaloblastic anemia is inevitable if

patients are not given prophylactic therapy (2). Low serum

vitamin B- I 2 concentrations after lesser gastric resections have

been attributed to poor absorption of protein-bound vitamin

B-l2, with absorption of crystalline vitamin B-l2 remaining

normal (3).

Such abnormally low serum vitamin B- 1 2 concentrations

have also been detected in > 25% of severely obese patients as

early as 1 y after gastric-limiting surgery for weight control

(4-9). Recent studies demonstrated malabsorption of protein-

bound vitamin B-l2 in patients after both gastric bypass and

vertical banded gastroplasty (10-I 2). Normal absorption of

crystalline vitamin B-l2 as measured by the Schilling test is

preserved, although the magnitude of absorption may be al-

tered after surgery (I I , 12). These authors speculate that the

surgical reduction of the size of the stomach leads to achlor-

hydria, and thereby maldigestion of vitamin B- 12 bound to

protein (I I). Others have suggested that the vitamin B- I 2

deficiency seen in these patients is due to inadequate secretion

of intrinsic factor (13).

Considerable evidence suggests that doses of vitamin B- 12

contained in standard multivitamin formulas (1-15 j.�g) are

insufficient for maintaining normal serum vitamin B- I 2 con-

centrations in these patients (6, 14). Provenzale et al (14) found

that the recommended dietary allowance (RDA) of 2 �g in

vitamin tablets taken orally was insufficient for maintenance of

vitamin B-12 status in 30% of the patients after gastric bypass.

Doses of oral vitamin B-I2 > 100 �g have been used in an

I From the Department of Surgery and Divisions of Hematology-

Medical Oncology and Clinical Biochemistry. Royal Victoria Hospital.

McGill University. Montreal, and the Department of Hematology. Stanford

University. Palo Alto, CA.

2 Organon Canada Ltd and CE Jamieson & Co Ltd supplied the Cotazym

and cyanocobalamin tablets.

3 Reprints not available. Address correspondence to BM Rhode. Royal

Victoria Hospital, 687 Pine Avenue West, Room H6.34, Montreal, Quebec,

Canada H3A lAl.

Received June 15, 1995.

Accepted for publication August 30. 1995.

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104 RHODE ET AL

effort to raise serum vitamin B-l2 concentrations into the

reference range (15, 16).

In light of the difficulty of maintaining serum concentrations

of vitamin B-l2 by oral ingestion, we set out to find a better

vehicle by which vitamin B-l2 could be given orally to patients

after gastric-limiting surgery for obesity. To this end, we iden-

tified patients with low serum vitamin B-I 2 concentrations and

normal findings after Schilling tests, and evaluated their ability

to absorb oral vitamin B- 12, either protein-bound or crystalline.

We also monitored the response of serum concentrations of

vitamin B-l2 to different doses of the oral vitamin in a separate

group of patients with low initial vitamin B-12 concentrations.

SUBJECTS AND METHODS

Surgical procedures

Two gastric-limiting procedures, vertical banded gastro-

plasty and Roux-en-Y gastric bypass (Figure 1, a and b), have

been used for the treatment of severe obesity since 1 982 at this

clinic. Patients with a preoperative body mass index (BMI; in

kgim2) > 40 and with complications of obesity were selected

for these operations, which were described in detail elsewhere

(17).

Experiment 1

Schilling tests and serum vitamin B-12 determinations were

performed on 47 patients (19 after gastroplasty; 28 after gastric

bypass) who appeared sequentially in our clinic over 4 mo. The

gastroplasty patients were 43 ± 9 y of age (3� ± SD), had a BMI

of 32 ± 7, had lost 32.6 ± 13.0% of their preoperative weight,

and had been followed for 3 1 .3 ± 26.6 mo after surgery. The

gastric bypass patients were 36 ± 8 y of age, had a BMI of 30

± 5, had lost 37.6 ± 8.9% of preoperative weight, and had

been followed for 23.3 ± 14.0 mo after surgery. All had a

normal finding from a Schilling test. Of the 47 patients, 13

( 1 man, 12 women) with serum vitamin B- 1 2 concentrations

below the lower reference limit for our institution at the time of

the study (< 200 pmolIL) were recruited. All had vitamin B-12

concentrations < 100 pmol/L, which is the vitamin B-12 value

most frequently associated with metabolic evidence of vitamin

FIGURE 1. Reprinted from reference 17. A: Vertical banded gastro-

plasty with division between the vertical staple lines. A Maloney bougie

no. 28 is in place and the polypropylene mesh band is 45-47 mm in

external circumference. B: Gastric bypass made with a 10- to 15-mL

gastric pouch placed in the dependent position. which encourages prompt

emptying. The Roux limb was 40 cm long and was placed in the retrocolic,

retrogastric position.

B- 1 2 deficiency ( 18). Of the 1 3 patients, 1 1 had had gastric

bypass and 2 had had vertical banded gastroplasty.

Experiment 2

Of the 13 patients identified in experiment 1, 8 women with

a low serum vitamin B-12 concentration volunteered to partic-

ipate in the second part of the evaluation of vitamin B-l2 status

using protein-bound vitamin B-12 absorption tests ‘�2 y after

the start of experiment 1. Three female hospital employees

volunteered to serve as control subjects. Measurements of the

following biochemical and hematologic indexes were made in

all subjects: electrolytes, urea, creatinine, glucose, calcium,

total protein, albumin, bilirubin, cholesterol, serum folate, vi-

tamin B-12, ferritin, homocysteine, and gastrin; liver-function

tests and a complete blood cell count were also performed. A

Schilling test was repeated in these eight patients before pro-

tein-bound vitamin B-l2 absorption tests were performed. The

integrity of the gastric pouch was verified by gastroscopy in all

patients.

Four weeks after the repeat Schilling test, a protein-bound

vitamin B-l2 absorption test using chicken serum was carried

out in the eight patients (see below). One month after the latter

test these patients were alternatively assigned to undergo one of

two vitamin B-l2 absorption tests. In the first test, patients

ingested pancrelipase preparation (Cotazym; Organon Canada

Ltd, Scarborough, Ontario) paste, which was washed down

with the chicken serum mixture. The paste was made with the

contents of three pancrelipase preparation capsules mixed with

dry coffee granules (see below). In the second test, patients

consumed a mixture of chicken serum and pancrelipase prep-

aration preincubated together before ingestion. The three con-

trol subjects underwent the protein-bound vitamin B-12 ab-

sorption tests in this order: chicken serum alone, chicken serum

followed by pancrelipase preparation paste, and chicken serum

preincubated with pancrelipase preparation. These absorption

tests were separated by 1-mo intervals.

The guidelines of the Royal Victoria Hospital Surgical Eth-

ics Committee were followed.

Vitamin B-12 absorption studies

Schilling test

Absorption of crystalline vitamin B-12 was measured with a

stage 1 Schilling test (19) and two sequential 24-h urine col-

lections, each preceded by an intramuscular injection of 1000

!_Lg unlabeled cyanocobalamin (Sabex Inc. Boucherville, Que-

bec), in patients after they had fasted overnight (20). A I .0-�tg

oral dose of [57Co]cyanocobalamin (37 GBq/g vitamin B-12)

was given as the free vitamin (Merck Frosst Canada mc,

Kirkland, Quebec). Radioactivity in urine was measured in a y

scintillation counter for 5 mm or 10 000 counts, whichever

came first. Results were expressed as the percentage of the

radioactive dose administered (reference range: 10-30%). The

total vitamin B-12 binding capacity and antibody blocking of

the intrinsic factor were measured in serum by the albumin-

charcoal method of Gottlieb et al (21).

Protein-bound vitamin B-12 absorption tests

Chicken serum [57Co]vitamin B-12

Blood from the jugular vein of one electrocuted chicken was

collected into a 750-mt glass jar at a poultry plant. Serum was

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VITAMIN B-12 DEFICIENCY AFTER OBESITY SURGERY 105

pipetted in 2-mL aliquots into glass vials and promptly frozen

at -20 #{176}C.On the day of the test, the oral dose was prepared

by mixing 1.0 �g [57Co]cyanocobalamin (37 GBqig vitamin

B-12) and 2 mL chicken serum. The mixture was incubated at

room temperature for 30 mm and diluted with tap water to a

final volume of 100 mL. The chicken serum had a vitamin

B-12 binding capacity of 0.75 mgIL. The fasting subjects were

first given the chicken serum mixture to drink and the remain-

der of the procedure was the same as that for the Schilling test.

Chicken serum pancre/ipase preparation paste

The contents of three pancrelipase preparation capsules were

mixed with 7.5 mL ( 1 .5 tsp) dry instant coffee and diluted with

sufficient tap water to form a paste. The paste was ingested and

washed down with the chicken serum solution described above.

Chicken serum pancre/ipase preparation incubation

Two milliliters of chicken serum was incubated with 1 .0 �g

[57Co]cyanocobalamin (37 GBq/g vitamin B-l2) in a lOO-mL

volumetric flask for 30 mm at room temperature. Three pan-

crelipase preparation capsules were opened and added to the

volumetric flask. Warm tap water was added and the solution

diluted to a final volume of 100 mL. This mixture was incu-

bated in a water bath (37 #{176}C)for 45 mm, with frequent agita-

tion. The incubated mixture was then ingested by the fasting

subjects.

Experiment 3

The response of serum vitamin B- 1 2 and serum total homo-

cysteine concentrations to oral ingestion of crystalline vitamin

B- 1 2 was assessed in an independent group of patients who had

had a gastric bypass. Ten patients (one man, nine women) with

low serum vitamin B-12 concentrations at a clinic visit were

recruited because of their ability to comply with the experi-

mental protocol. They were asked to refrain from donating or

having blood drawn at other centers during this time. The first

part of this experiment consisted of the patients ingesting 4 jtg

oral crystalline vitamin B-l2id for 3 mo. It was administered as

two drops on a sugar cube twice a day, in the morning and

evening. This preparation was made by diluting parenteral

vitamin B- 1 2 ( 1 g cyanocobalaminlL; Sabex Inc) in sterile

water (1 :50) to yield a concentration of 1 pg/drop. The solution

was dispensed with plastic droppers from 20-mL brown glass

bottles. The stability of the cyanocobalamin solution was mon-

itored bimonthly over the 3-mo period by the laboratory using

a radiodilution assay.

Before the start of the experiment, patients were shown how

to add the crystalline vitamin B-l2 drops to the sugar cube.

They were instructed to consume the crystalline vitamin B- 12

after fasting. No ascorbic acid-containing foods were allowed

within 2 h of the ingestion of these drops. Special attention was

paid to chewing the sugar cube and mixing it with saliva in the

mouth for several minutes before swallowing. This was fol-

lowed by ingesting � 240 mL tap water each time.

In the second part of the experiment, 10 patients ingested

350 �tg crystalline vitamin B- 1 2id for 3 mo in the form of

vitamin B-l2 tablets (CE Jamieson & Company Limited,

Windsor, Ontario). Instructions for taking the crystalline vita-

mm B- 12 were the same as described previously.

Laboratory techniques and other items

Biochemical indexes were analyzed on a Technicon SMAC

II analyzer (Miles Inc. Diagnostic Division, Tarrytown, NY)

using reagents supplied by the manufacturer. Blood counts

were done with a Technicon H 1 (Miles Inc. Diagnostic Divi-

sion). Serum vitamin B-12 and folate concentrations were

assayed by using the Quantaphase radioassay technique

(Bio-Rad Laboratories Ltd. Mississauga, Ontario). Serum fer-

ritin was determined with the Fer-Iron MT kit (Ramco Labo-

ratories Inc, Houston). Serum total homocysteine was mea-

sured by the method of Chadefaux et al (22). To evaluate the

functional status of the gastric mucosa, serum gastrin was

measured with a commercially available radioimmunoassay kit

(Becton Dickinson and Co, Orangeburg, NY). Each capsule of

the pancrelipase preparation contained 8000 USP units of

lipase activity, 30 000 USP units of amylase activity, and

30 000 USP units of protease activity.

Statistical analysis

Statistical procedures performed included Spearman’s rank

correlation, paired and unpaired Student’s t tests and chi-square

and nonparametric analyses. Data are reported as means ±

SDs. INSTAT for Macintosh (version 2.03; Graph Pad Soft-

ware, San Diego) was used for the statistical analyses.

RESULTS

Experiment 1: absorption of crystalline vitamin B-12

Schilling test results of 47 patients with serum vitamin B-12

concentrations < or � 100 pmolIL 26.5 ± 20.4 mo after

vertical banded gastroplasty or gastric bypass are illustrated in

Figure 2. These two groups had significantly different serum

vitamin B-l2 concentrations (244 ± I 55 compared with I 66 ±

161 pmolIL; P = 0.0143) and ages (43.1 ± 9.4 compared with

36.3 ± 8.1 y; P = 0.0176), respectively. Schilling test results

were not significantly different between groups (28.8 ± 5.9%

compared with 24.9 ± 8.7%; P = 0.0593); all patients had

values within or above the reference range (10-30%). All

patients who excreted radioactive vitamin B- I 2 concentrations

greater than the reference range had normal serum vitamin

B- 1 2 concentrations, whereas 41 % of all patients whose excre-

tion values were within the reference range had low values

(P = 0.020). There was no detectable relation between per-

centage urinary excretion, current BMI, percentage weight

<100 �100 <100 �100

Vitamin B.12 (pmoIJL)

FIGURE 2. Percentage l57Colvitamin B-12 excreted per 48 h as a

function of serum vitamin B- I 2 concentration. Vertical banded gastro-

plasty (0): n = 2 < 100 pmolIL and ii = 17 � l()0 pmol/L. Gastric bypass

(LI):n = I 1 < 100 pmol/L and a = 17 � 100 pmol/L.

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I 06 RHODE ET AL

loss, follow-up time, and type of surgery (r < 0.40). Schilling

test results correlated with serum vitamin B-I2 concentrations

(r 0.49; P = 0.0009) and age, with older patients excreting

the most radioactive vitamin B-12 concentrations (r = 0.45,

P = 0.0013). Of 13 patients with low serum vitamin B-l2

status, 5 were taking multivitamins containing � 2 p.g crystal-

line vitamin B-12.

Experiment 2: effect of various ingested agents onurinary excretion of radioactive vitamin B-12

Clinical data on the eight patients with a low serum vitamin

B- I 2 concentration and three control subjects who underwent

the standard Schilling and protein-bound vitamin B-12 absorp-

tion tests are shown in Table 1. Only one patient was obese at

the time of study (BMI > 35). Protein-bound absorption stud-

ies were done 30.4 ± 1 1 .8 mo (range: 8-49 mo) after surgery.

Seven patients had had a gastric bypass (Figure lb) and one

had had a gastroplasty (Figure la). The control subjects were

free of gastrointestinal complaints and had had no abdominal

operations. Two patients were not taking any vitamin supple-

ments during the study. Four were taking a standard multivi-

tamin and ferrous sulfate supplement of 300 mg twice daily.

Two took only the multivitamin. Six of eight patients were

taking a brand of multivitamins containing S ig vitamin B-12i

tablet.

All patients had one or more abnormalities of serum folate,

ferritin, or vitamin B-l2 concentrations. Anemia was seen in

five patients and in one control subject. Serum ferritin concen-

trations were depressed in these anemic patients and in the one

control subject, indicating depleted iron stores. Low serum

folate values were seen in two patients. Two other patients had

just completed a 3-mo supplementation period with folic acid,

S mg three times daily. Although serum vitamin B-12 concen-

trations rose during the 2-y period before the protein-bound

absorption tests in all but one patient, they remained below the

reference range (67 ± 15 compared with 100 ± 27 pmol/L;

P = 0.008). One patient had been receiving parenteral vitamin

B- 12 for I y but the patient stopped supplementation when the

study began. Dietary intake of vitamin B-l2-containing foods

had not changed substantially over this 2-y period. Intrinsic

factor antibodies were not detected in any study subject. Serum

TABLE 1Clinical data in subjects undergoing vitamin B-l2 absorption tests’

Reference

Range

Control.

subjects� = 3)

.Patients

�“ 8)

Age (y) 37.3 ± 5.3 36.0 ± 6.7

BMI (kg/m2) - 22 ± 4 30 ± �2

Time postoperative (mo) - - 30.4 ± 11.8

Hemoglobin (gIL) 120-160 131 ± 12 112 ± 122

MCV (IL) 81-99 88.1 ± 3.4 81.2 ± 8.6

Serum femtin (fLg/L) 20-200 17 ± 9 3 ± l�

Serum folate (nmollL) 9-45 19.1 ± 6.3 16.9 ± 11.5

Serum vitamin B-l2 (pmol/L) 200-740 370 ± 165 100 ± 27�

Serum homocysteine (�molIL) < 24.0 9.1 ± 1.6 11.8 ± 2.4

Serum gastrin (ngIL) 0-1(X) 40.5 ± I 1.2 48.2 ± 20.0Ij� � SD. MCV, mean corpuscular volume.

2-4 Significantly different from control subjects (unpaired two-tailed t

test): 2P = 0.04, ‘P = 0.001, ‘P = 0.0008.

homocysteine concentrations and serum gastrin values were all

within the reference range.

Table 2 shows the results of protein-bound vitamin B-l2absorption in patients and control subjects. Absorption of crys-

talline vitamin B-12 from the Schilling test was significantly

higher than that of the protein-bound vitamin from chicken

serum in the eight patients (P < 0.0001). Patients had a

significantly lower mean vitamin B-12 absorption rate from

chicken serum when compared with control subjects (P <

0.001). Values for absorption of vitamin B-12 from chicken

serum for the control subjects were similar to those reported

previously (10, 23, 24). When enzyme paste was ingested with

the chicken serum, the patients again had a significantly lower

absorption rate when compared with control subjects (P =

0.028). In contrast, there was no statistical difference in ab-

sorption of vitamin B- 1 2 between patients and control subjects

when the chicken serum was incubated in vitro with the en-

zyme mixture before ingestion (P = 0.106).

[57Co]Vitamin B-12 excretion was not significantly different

between patients who ingested chicken serum with and without

enzyme paste (P = 0.54). The change in control subjects was

significantly higher than the change induced in patients (3.87

± 3.51% compared with -0.09 ± 0.25%; P = 0.034). With

preincubation of chicken serum and pancrelipase preparation

before ingestion, absorption as indicated by an increased

[57Co]vitamin B-12 excretion increased for both patients and

control subjects (1.55 ± 1.32% compared with 3.13 ± 2.92%;

P = 0.48).

Experiment 3: response to orally administered crystallinevitamin B-12

Ten patients (one man, nine women) aged 40 ± 10 y with a

low serum vitamin B- 12 concentration and a BMI of 27 ± 4

were studied 19.4 ± 6.5 mo after gastric bypass. Only one

patient was obese. One woman was being treated for micro-

cytic anemia with 300 mg ferrous sulfate three times daily. All

patients were taking standard multivitamins.

Three months of a daily dose of 4 jtg crystalline vitamin

B- 12 did not increase mean serum vitamin B- 1 2 concentrations

to the reference range (> 200 pmol/L; P = 0.086) (Table 3).

The 350-p.g dose raised mean serum values into the reference

range (P < 0.01), but still failed to correct the serum vitamin

B-12 concentration in S of 10 patients. Serum homocysteine

TABLE 2Percent urinary excretion of radioactive vitamin B-12 in control subjects

and patients’

Absorption tests Control subjects Patients

Schilling - 19.8 ± 6.0 [8]

Chicken serum 2.4 ± 0.7 [3] 0.4 ± 0.4 [8]24

Enzyme paste 6.3 ± 4.1 [3] 0.2 ± 0.2 [4]3

Incubation 5.5 ± 3.2 [3] 2.0 ± 1.5 [4]5

‘ i ± SD; pi in brackets. Vitamin B- 12 absorption tests were separated

by � I-mo intervals.

2.3 Significantly different from control subjects (unpaired t test): 2 p <

0.001, 3P = 0.028.

4 Significantly different from control subjects, P = 0.0121 (Mann-

Whitney test).

5 Not significantly different from control subjects, P = 0.106 (unpaired

I test).

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VITAMIN B-12 DEFICIENCY AFTER OBESITY SURGERY 107

TABLE 3Response of vitamin B- 12 and serum total homocysteine concentrations

to oral ingestion of 4 and 350 �.tg crystalline vitamin B-12 for 3-mo

periods’

Vitamin B-12 status Before ingestion 4 �g 350 �g

Serum vitamin B- I 2

(pmol/L) 87 ± 252 124 ± 43’ 214 ± 88�

Serum homocysteine

(�mol/L) 18.2 ± 5.0 12.5 ± 2.0� 13.4 ± 3.5�‘3�±SD;n= 10.

2.3 Significantly different from 350-pg value (Tukey Kramer posttest):

2P<0.00l,3P<0.Ol.

4 Overall P < 0.001 for comparison among serum vitamin B-12 con-

centrations by paired ANOVA.

5 Significantly different from before-ingestion value, P = 0.0064

(Welch test).

On = 5.

decreased in 9 of 10 patients with the 4-�tg dose of crystalline

vitamin B-12 (P = 0.0064). The increased dose of 350 p.g

vitamin B-l2 did not lead to further lowering of serum total

homocysteine (P = 0.5026).

DISCUSSION

Vitamin B-12 deficiency as measured by a low serum con-

centration has been described in 26-70% of patients within 2 y

after gastric bypass for obesity (4-9). Of 193 patients followed

for 1-2 y in our clinic, the serum vitamin B- 1 2 concentration

was below the lower limit of the reference range in 57 patients

(30%).

This study supports the findings of Yale et al (10) and Smith

et al (1 1), who showed malabsorption of protein-bound vitamin

B-12 but normal absorption of crystalline vitamin B-l2 as

measured by the Schilling test. Behrns et al (12) found that

crystalline vitamin B- I 2 absorption was decreased after gastric

bypass surgery, albeit remaining within the reference range,

suggesting that less intrinsic factor was available for binding of

vitamin B- 1 2 after surgery than before. Various authors have

suggested various causes for these observations, including poor

mixing of the vitamin with intrinsic factor beyond the jejunoje-

junal junction, insufficient secretion of intrinsic factor, or pro-

teolytic destruction of intrinsic factor before it had a chance to

bind with vitamin B-12. In our study, the simultaneous inges-

tion of protein-bound vitamin B-12 with an enzyme paste did

not improve absorption of the vitamin. This suggests that the

upper gastrointestinal tract after gastric bypass does not favor

enzymatic activity to free protein-bound vitamin B-l2, likely

because of both rapid transit and achlorhydria.

This absorption defect was partially corrected when protein-

bound vitamin B- 12 was incubated with an enzyme mixture

before ingestion. Sufficient vitamin B-l2 was made available

in the chicken serum to produce increased absorption in two of

three control subjects and in all four patients. The change in

absorption from chicken serum alone was greater in control

subjects than in patients, indicating that the vitamin B-12 that

had been released by the incubation process was not as easily

utilized by patients as it was by control subjects.

These data suggest that vitamin B-l2 may not be sufficiently

available to meet the vitamin requirements of these patients.

Consumption of enzymes with foods to effect release from

proteins, or incubation of foods before ingestion, are not fea-

sible alternatives for providing the vitamin. Therefore, supple-

mentation is required, an issue that we addressed in the latter

part of our study.

Despite that normal phase- 1 Schilling tests indicated absorp-

tion of crystalline vitamin B-12 in these patients, treatment

with multivitamin preparations containing the RDA did not

prevent or ameliorate existing low vitamin B- I 2 concentra-

tions. This confirms the findings of Provenzale et al (14). The

use of twice the RDA for vitamin B- 1 2 for 3 mo was also

ineffective in correcting low serum vitamin B-l2 concentra-

tions. It is unclear why serum vitamin B- 12 did not increase

significantly or at all in patients taking 4 p�g oral crystalline

vitamin B-l2id, but serum homocysteine did decrease in these

patients, suggesting that vitamin B-l2 was being utilized. Cor-

rection of low concentrations of vitamin B- 1 2 by oral admin-

istration of physiologic amounts (1-10 p�g) of vitamin B-l2

requires the mediation of intrinsic factor.

The use of 350 p.g cyanocobalamin produced a serum vita-

mm B-12 concentration greater than the lower reference limit

in one-half of our patients, but the other one-half still had low

concentrations after 3 mo. Other studies from this clinic sug-

gest that all patients can be treated successfully with oral

vitamin B-12 if doses are increased to 600 .tgid ( 16), doses that

far exceed the capacity of the vitamin B- I 2 intrinsic factor

absorption mechanism (25).

Is this lowered serum concentration of vitamin B- 1 2 clini-

cally significant? Many studies support the idea that low serum

concentrations and a normal result from a Schilling test are

frequently encountered and can be accompanied by significant

neuropsychiatric complications without the development of

megaloblastic anemia, which was absent in our patients (26).

Serum homocysteine concentrations can be used as a mea-

sure of the tissue concentrations or functional abundance of

vitamin B-12. This may differ from the abundance indicated by

the serum concentrations of the vitamin because homocysteine

catabolism is a function of the activity of both vitamin B- 12-

dependent methionine synthase and pyridoxal phosphate-

dependent cystathione J3-synthase. Consequently. during vita-

mm B-12 depletion homocysteine accumulation may occur

only at a later stage in the process (27). One can only speculate

that patients in this study, despite having low serum vitamin

B- 12 concentrations, were not fully depleted of tissue vitamin

B- I 2 concentrations as evidenced by serum homocysteine con-

centrations below the upper reference limit (Table 3). That they

did respond to vitamin B-l2 with a reduction in homocysteine

concentrations suggests that they were not fully replete.

This study does not explain why our patients had a normal

result from a Schilling test, indicating normal absorption of

crystalline vitamin B- I 2, but at the same time, a low serum

concentration despite the administration of two times the RDA

or even 350 �g vitamin B-l2id for 3 mo.

There are examples in the literature of discrepancies between

results of the Schilling test and serum vitamin B- I 2 concen-

trations. Pancreatic insufficiency does interfere with the normal

process of absorption of vitamin B- 1 2 as reflected by abnormal

Schilling test results in nearly all patients with cystic fibrosis.

Despite the frequency of abnormal Schilling test results, vita-

mm B- 12 deficiency is very rare in cases of exocrine pancreatic

dysfunction (28). Partial or subtotal gastrectomy can lead to

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108 RHODE ET AL

vitamin B- 12 deficiency over time and this is frequently asso-

ciated with normal absorption of crystalline vitamin B-l2 (29,

30). Likewise, atrophic gastritis successively decreases produc-

tion of gastric acid, pepsin, and intrinsic factor. These patients

absorb crystalline vitamin B-12 but develop a serum vitamin

B- I 2 deficiency in 14-22% of cases (3 1 ). All patients in this

study had normal serum gastrin concentrations, indicating a

normal intrinsic factor production (32).

Schilling (33) stated that testing a patient’s ability to absorb

the vitamin will not establish the diagnosis of deficiency per se.

There can be a substantial decrease in the binding of intrinsic

factor to vitamin B- 12 after gastric bypass concomitant with a

normal Schilling test result because it takes only 10% of

normal intrinsic factor secretion for the absorption of 0.5-1.5

,.Lg vitamin B-l2-the amount used for the crystalline vitamin

B- 1 2 absorption test (34).

Vitamin B-l2 deficiency is less likely after vertical banded

gastroplasty because there is no diminution of acid production

and the food passes via the usual route. In this study, only 2 of

19 patients with gastroplasty had low serum vitamin B-12

concentrations (Figure 2). These patients had normal Schilling

test results. Further experience in this clinic indicated a low

serum vitamin B- I 2 concentration in S of 63 gastroplasty

patients (8%) followed-up for 67.6 ± 12.4 mo. Why these

patients had a deficiency of vitamin B-I2 cannot be explained

by the arguments used above to explain the deficiency in

patients after gastric bypass. One gastroplasty patient in this

series showed impaired absorption of protein-bound vitamin

B- 1 2. Yale et al (10) also found decreased protein-bound

vitamin B- 12 absorption after gastroplasty, but this defect was

less severe than after gastric bypass. It was corrected by boiling

the chicken serum before ingestion, which was not so after

gastric bypass. Many patients do not consume foods rich in

vitamin B-12, especially meat, after vertical banded gastro-

plasty. We also know that vegetarians are at high risk for

vitamin B-l2 deficiency over long periods of time.

Patients frequently and rapidly develop a serum vitamin

B-l2 deficiency after gastric bypass. This is due to a failure to

absorb protein-bound vitamin B- 12. Despite a normal result

from the Schilling test, not all the deficient patients corrected

their serum concentrations with doses of oral crystalline vita-

mm B- 12 that were equal to the RDA (2 jtg ingested twice

daily or 350 �gid, each taken for 3 mo). A dose > 350 p.g/d

was necessary to increase serum vitamin B-12 concentrations

to values greater than the lower reference limit in every patient.

The therapeutic dose of vitamin B-12 required far exceeds that

explainable by the vitamin B-12 intrinsic factor mechanism. Oral

treatment of vitamin B-l2 deficiency after gastric bypass is effec-

tive, but at doses much larger than stipulated by the current

nutritional guidelines. A vitamin B-12 deficiency after gastro-

plasty is much less common. The mechanism is not as yet clear

but dietary insufficiency is a distinct possibility. El

We are indebted to Saul Katz, Division of Gastroenterology. Royal

Victoria Hospital, for assistance with the study design; Helena Lue Shing

and David Rosenblatt, Division of Medical Genetics, for serum total

homocysteine analysis: Erica Jonas and Valerie Feherdy for blood folate

and vitamin B- I 2 analyses; Christiane Jacques and Lucie Desautels, Phar-

macy. for preparation of the low-dose oral cyanocobalamin solution; Gisele

Pouliot for the Schilling tests; and Paul C Lague. Department of Animal

Science, McGill University, for advice on processing the chicken blood.

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