PEDIATRICS Vol. 122 No. 1 July 2008, pp. 83-91 (doi:10.1542/peds.2007-2716)
ARTICLE |
Common Metabolic Profile in Infants Indicating Impaired Cobalamin Status Responds to Cobalamin Supplementation
a Departments of Clinical Biochemistry
b Pediatrics, Haukeland University Hospital, Bergen, Norway
c Section for Pharmacology, Institute of Medicine, University of Bergen, Bergen, Norway
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ABSTRACT |
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OBJECTIVE. A metabolic profile consistent with impaired cobalamin status is prevalent in breastfed infants. We investigated whether this profile reflects immature organ systems or impaired cobalamin status.
METHODS. In a single-center, randomized, placebo-controlled trial, we studied 107 six-week-old infants. The infants were randomly assigned to receive either an intramuscular injection of 400 µg of cobalamin or no intervention. Concentrations of cobalamin and folate in serum and total homocysteine, methylmalonic acid, and cystathionine in plasma were determined at enrollment and at the age of 4 months.
RESULTS. There were no significant differences between the intervention group (n = 54) and the control group (n = 53) in the concentrations of any vitamin marker at baseline (6 weeks). At 4 months, the supplement-treated infants had a 75% higher median serum cobalamin level and remarkable reductions in median plasma total homocysteine (from 7.46 to 4.57 µmol/L) and methylmalonic acid (from 0.58 to 0.20 µmol/L) levels, whereas levels of both metabolites were essentially unchanged during the follow-up period in the control group.
CONCLUSIONS. Cobalamin supplementation changed all markers of impaired cobalamin status (low cobalamin, high total homocysteine, and high methylmalonic acid levels) toward a profile observed in cobalamin-replete older children and adults. Therefore, the high total homocysteine and methylmalonic acid levels reported for a large fraction of infants reflect not immature metabolism but rather insufficient cobalamin levels to fully sustain cobalamin-dependent reactions fully.
Key Words: infant • breastfeeding • cobalamin deficiency • cobalamin supplementation
Abbreviations: tHcy—total homocysteine • MMA—methylmalonic acid
There has been increasing awareness of cobalamin deficiency in breastfed infants.1–3 In exclusively breastfed infants, the cobalamin content in the milk, and therefore the maternal cobalamin status during lactation, has a profound impact on the infant cobalamin status.4 Infant cobalamin deficiency is considered secondary to maternal deficiency, which may be attributable to vegetarianism, malabsorption, or unrecognized early pernicious anemia.5
High rates of cobalamin deficiency in pregnant and breastfeeding women and their infants have repeatedly been demonstrated in developing countries.1,6–9 In developed countries, exclusive breastfeeding for the first 6 months is encouraged,10 and this places great nutritional demands on the mother.11
During fetal life and infancy, adequate cobalamin status is important for normal growth and central nervous system development.2 In infants, cobalamin deficiency may present as failure to thrive, developmental delays or regression, progressive or persistent neurologic disorders, or hematologic changes. The symptoms may be evident as early as 3 weeks of age but often are subtle and difficult to detect, partly because of the large variation in normal development in this age group.12–16 Long-term neurologic consequences depend on the severity and duration of cobalamin deficiency, but deficiency during infancy, even when treated successfully, may result in permanent developmental disabilities.14,17–19
Cobalamin is a coenzyme in a folate-dependent methyl transfer reaction that converts homocysteine to methionine and in a separate reaction that converts L-methylmalonyl-CoA to succinyl-CoA. Consequently, elevated levels of total homocysteine (tHcy) and/or methylmalonic acid (MMA) in the blood are measures of impaired cobalamin status.20 Homocysteine also can be condensed with serine to form cystathionine,21 and elevated levels of cystathionine are found in the serum of most patients with cobalamin and folate deficiencies.22
There have been reports of low cobalamin concentrations combined with elevated concentrations of the metabolic markers tHcy and MMA in apparently healthy, breastfed infants born to mothers on a westernized diet.23–27 This metabolic profile may be an innocuous phenomenon caused by immaturity of liver or kidney function28,29 or may reflect common occurrence of impaired cobalamin function in infants.2,30,31
We conducted a randomized, controlled, cobalamin intervention trial with infants 6 weeks of age. The purpose of the study was to determine whether cobalamin supplementation influenced the metabolic profile related to cobalamin status in infants.
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METHODS |
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Study Population and Design
Healthy term infants and their mothers were recruited by a local public health nurse during well-infant visits at 5 different health services. Between December 2004 and April 2006, 107 healthy infants, including 3 pairs of twins, and their 104 mothers were enrolled. The infants were 6 ± 2 weeks of age at entry. They were invited back for a second investigation at 4 months of age. At baseline and 4 months, blood samples were obtained from infants and mothers through antecubital venipuncture. A questionnaire on infant and maternal nutrition, vitamin supplementation, growth parameters, parity, and maternal use of tobacco was completed.
Infants were assigned, through block randomization, to receive either cobalamin (n = 54) or no treatment (n = 53; control group). Four infants were lost to follow-up monitoring, 2 from each group. After blood sampling at the first visit, the infants in the intervention group received an intramuscular injection of 400 µg of hydroxycobalamin (vitamin B12 depot; Nycomed Pharma, Zürich, Switzerland). Treatment with 400 µg of hydroxycobalamin has been associated with increased hemoglobin levels32 and reduced tHcy and MMA levels in premature infants (A-L.B-M., T.M., H. Reigstad, P.M.U., unpublished data, 2003).
Because of ethical concerns, no placebo injection was given to the control subjects. The laboratory personnel responsible for blood sampling and analyses but not the rest of the study staff members or the mothers were blinded with respect to group assignment. Ethical approval of the protocol was granted by the local committee on medical research ethics, and the mothers gave written informed consent.
Blood Sample Collection and Biochemical Analyses
Serum was obtained by collecting blood into Vacutainer tubes (Becton Dickinson, Franklin Lakes, NJ) with no additive. Blood was allowed to clot at room temperature for 30 minutes before the serum fraction was transferred to an empty glass vial. The blood samples used for preparation of EDTA-treated plasma were collected into Vacutainer tubes (Becton Dickinson, Franklin Lakes, NJ) and placed in ice water, and plasma was separated within 4 hours. The samples were stored at –80°C until analysis.
Serum cobalamin levels were determined with a Lactobacillus leichmannii microbiologic assay33 and serum folate levels with a Lactobacillus casei microbiologic assay.34 Plasma levels of tHcy, MMA, and cystathionine were determined by using a gas chromatography-mass spectrometry method based on methylchloroformate derivatization.35
Statistical Analyses
The calculation of the sample size was based on data from our previous studies23,26 on cobalamin status in infants, with the assumption that cobalamin supplementation would result in tHcy levels located in the lower quartile (<6.14 µmol/L) for infants at 4 months. A calculated sample size of 65 (ie, 33 in each group) would give the study a statistical power of >90% to detect a 25% relative reduction in tHcy levels. However, on the basis of our experience from earlier studies, a dropout rate of 
40% was expected, and a total of 100 infants were recruited.
Results are presented as median and interquartile range and mean ± SD. Medians were compared with the Wilcoxon signed-ranks test and Mann-Whitney U test, and means were compared with Student's t test. Differences in categorical variables were tested with the 
2 test. Multivariate linear regression models were used to assess the relationships of intervention, infant nutrition, and maternal vitamin status to infant serum cobalamin, serum folate, plasma tHcy, MMA, and cystathionine levels at 6 weeks and 4 months. Because the additional solid food (cereals) used at 4 months did not contain cobalamin, infant nutrition was defined as breastfed, combined breastfed and formula-fed, or formula-fed.
We also used quantile regression analysis,36 which examines the simultaneous influence of the covariates on the entire distribution of metabolic responses of the infants, to determine changes in infant cobalamin, folate, tHcy, or MMA levels as a function of pretreatment concentrations of these variables at 6 weeks, intervention, infant nutrition at 4 months, maternal cobalamin concentrations at 4 months, and, for changes in infant folate and tHcy levels, maternal folate levels at 4 months. For each covariate, the point estimate is the impact of a 1-unit change in the covariate on infant vitamin or metabolite concentrations at 4 months, with the other covariates held fixed. Because the respective infant indices at 6 weeks were included as independent variables, the outcome measure was the change in infant indices from 6 weeks to 4 months.
Two-sided P values of <.05 were considered statistically significant. SPSS 11 (SPSS, Chicago, IL) was used for all statistical analyses except for quantile regression analysis, for which R37 was used.
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RESULTS |
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Demographic Features and Nutrition
The total group included healthy term infants with birth weight (mean ± SD) of 3560 ± 513 g, birth length of 50.5 ± 2.0 cm, and head circumference at birth of 35.1 ± 1.5 cm. More infants were exclusively breastfed in the intervention group than in the control group (P = .052). Apart from this, there were no significant differences (P = .29-.99) between the infant groups with respect to baseline characteristics (Table 1).
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At 6 weeks (Table 1), all infants were exclusively milk fed, 86 of 107 were exclusively breastfed, none received additional solid food, and daily multivitamin supplements (not including cobalamin) were given to only 1 infant. The 2 different kinds of milk formula used were both enriched with cobalamin, at 0.13 µg per 100 mL of prepared milk formula (Collet; Axellus, Norway) or 0.2 µg per 100 mL of prepared milk formula (Nan; Nestlé, Norway).
At 4 months (Table 2), 72 of the 103 infants (39 from the intervention group and 33 from the control group) were exclusively breastfed. The remaining 31 infants (13 from the intervention group and 18 from the control group) received formula either additionally or exclusively and/or cereal. None of the cereals used was enriched with cobalamin. Only 1 infant (control group) received dinner, and daily multivitamin supplements were given to 2 infants (1 from each group); none of these supplements contained cobalamin.
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Maternal age, BMI, parity, vitamin supplement use, and smoking habits at 6 weeks were not significantly different between the intervention group and the control group (Table 1). Two of the mothers were vegetarians, and the others claimed to have an omnivorous diet, although 9 mothers reported that they rarely or never ate meat (n = 6) or fish (n = 3).
Infant Blood Indices and Effects of Intervention
There were no gender differences in serum cobalamin or folate levels or the metabolic markers plasma tHcy, MMA, and cystathionine levels (all P > 0.1; data not shown), and the data for both genders were analyzed together. Before intervention, the concentrations of the B vitamins and metabolites were not significantly different between the intervention group and the control group (Table 3).
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During the follow-up period (between 6 weeks and 4 months), median serum cobalamin levels increased markedly (from 172 to 421 pmol/L) in the infants given cobalamin and moderately (from 170 to 240 pmol/L) in the control infants. Serum folate levels increased in both groups during this period but less so in the intervention group (from 21.7 to 35.2 nmol/L), compared with the control group (from 23.7 to 47.9 nmol/L). At 4 months, the median serum folate level was significantly lower in the intervention group (Table 3 and Fig 1).
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The most notable effects of cobalamin intervention were considerable reductions in plasma tHcy, MMA, and cystathionine levels during the follow-up period (Table 3 and Fig 1). In the intervention group, the median plasma tHcy level was reduced from 7.46 to 4.57 µmol/L (39%), plasma MMA level from 0.58 to 0.20 µmol/L (66%), and plasma cystathionine level from 0.46 to 0.16 µmol/L (65%). In the control group, plasma tHcy and MMA levels remained stable and the plasma cystathionine level decreased from 0.46 to 0.24 µmol/L (48%) (Table 3 and Fig 1).
We observed that, at 4 months, 35 of 51 control infants had plasma tHcy levels above the 97.5th percentile (6.50 µmol/L) of the tHcy levels in the supplement-treated infants. Approximately the same proportion, 73 of 107 infants, had tHcy levels of >6.50 µmol/L at baseline. Therefore, more than two thirds of young infants had a metabolic profile consistent with impaired cobalamin status that could be corrected with cobalamin supplementation. No adverse effects of the cobalamin injections were reported.
Determinants of Infant B Vitamin Status Before and After Intervention
In the multivariate linear regression analyses (Table 4), maternal cobalamin level was a strong predictor of infant serum cobalamin and plasma tHcy levels before intervention (6 weeks). At 4 months, cobalamin intervention was by far the strongest predictor of infant cobalamin status, as determined by cobalamin, tHcy, and MMA levels. Intervention also predicted serum folate and plasma cystathionine concentrations (Table 4).
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In the control group at 4 months, maternal cobalamin level and infant nutrition were strong predictors of infant serum cobalamin (P < .001 and P < .001, respectively) and plasma tHcy (P < .001 and P = .008, respectively) levels. Maternal cobalamin level was also a predictor of cystathionine levels (P = .001) (data not shown).
Determinants of Infant Metabolic Responses
Changes in infant cobalamin, folate, tHcy, and MMA levels from 6 weeks to 4 months according to intervention, concentrations of these indices at 6 weeks, infant nutrition at 4 months, and maternal cobalamin and folate levels at 4 months were determined through quantile regression (Fig 2). Separate analyses were conducted for each infant blood index.
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Intervention was the strongest predictor of changes for all blood indices. The largest increase in cobalamin levels and the largest decreases in tHcy and MMA levels were observed in the upper quantiles of these variables, whereas the folate responses (reduction) were similar throughout the folate level distribution. Cobalamin, folate, tHcy, and MMA levels at 6 weeks showed a weak positive relationship with changes in these indices from 6 weeks to 4 months; the strongest associations were observed at the highest quantiles of folate, tHcy, and MMA levels. Infant nutrition had a moderate positive association with changes in cobalamin levels and a minor effect on the other indices. Maternal cobalamin and folate levels showed no or only weak associations with changes in infant indices (Fig 2).
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DISCUSSION |
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Overall Findings
Apart from case reports on cobalamin-deficient infants,38–40 no cobalamin intervention study with infants or younger children has been published previously. In the present study of predominantly breastfed, healthy, term infants, an intramuscular injection of 400 µg of cobalamin at 6 weeks of age resulted in higher serum cobalamin levels and markedly lower plasma tHcy and MMA concentrations at 4 months of age, compared with control values. Folate and cystathionine levels were lower at 4 months among those who received cobalamin. Our results show that cobalamin supplementation can normalize a metabolic profile consistent with impaired cobalamin status in young infants.
Study Design and Limitations
It is a formal weakness of the study design that the control group did not receive placebo medication and the investigators and the mothers were not blinded to the cobalamin injection. These decisions were attributable to ethical constraints.
From a theoretical perspective, it would have been desirable to study whether cobalamin supplementation had an effect on psychomotor development. Neurodevelopmental assessment was not attempted, however, because even detailed examinations are not sufficiently accurate to detect mild or moderate developmental delays in young infants.41
Vitamin and Metabolite Concentrations at Baseline
The metabolic profile at 6 weeks of age (ie, low cobalamin and high folate, tHcy, and MMA levels) (Table 3) was consistent with previous reports for infants.23–25 During the first months of life of term infants, serum cobalamin levels decrease,23,42,43 whereas serum folate levels tend to increase.26,44,45 Compared with data for children 1 to 10 years of age,26 the median serum level of cobalamin at 6 weeks was low (170 vs 551 pmol/L), whereas the median folate level was high (22.2 vs 14.9 nmol/L). The plasma concentrations of tHcy at 6 weeks were in the range of 6 to 9 µmol/L, as observed previously for young infants,23,25,26,46,47 and were much higher than the concentrations of 3 to 8 µmol/L found for 1- to 10-year-old children.26,48–51 In the present study and in previous studies,23,26 the median plasma level of MMA in infants was 2 times higher than the upper reference limit of 0.28 µmol/L established for adults52 and was considerably higher than MMA levels reported for 1- to 10-year-old children (median: 0.13 µmol/L; range: 0.11–0.17 µmol/L).26 High urinary MMA excretion and plasma MMA levels have been reported consistently for breastfed infants up to the age of 6 to 12 months23,26,53 and infants of mothers on a vegetarian diet.54 Data on plasma cystathionine levels in infants are scarce, but the observed median plasma cystathionine levels at 6 weeks (0.46 µmol/L) were comparable to reported concentrations in cord serum at birth.55
Effects of Intervention on B Vitamin Status
Whereas the metabolic markers of cobalamin status were unchanged in the control subjects between 6 weeks and 4 months, the reductions in tHcy (39%) and MMA (66%) concentrations in the cobalamin supplement-treated infants were remarkable (Table 3 and Fig 1). These findings are in accordance with reports of lower tHcy and MMA levels in infants given cobalamin supplements or formula, which usually contains higher cobalamin concentrations than human milk.24,25,53,56
The infants given cobalamin had lower folate levels, compared with the control subjects, at 4 months (Table 3). High serum folate levels have been observed in early cobalamin deficiency in adults57 and have been attributed to so-called methylfolate trapping. This is explained by increased 5-methyltetrahydrofolate levels in serum/plasma because of inhibition of the cobalamin-dependent enzyme methionine synthase.58
We observed a larger reduction in cystathionine levels in the cobalamin supplement-treated infants (65%), compared with the control subjects (48%) (Table 3). Cystathionine levels were reported to be elevated in 87% of adults with cobalamin deficiency and 95% of adults with folate deficiency and were found to decrease in response to cobalamin or folate treatment in some22 but not all59 studies. Increased urinary cystathionine levels were reported for an infant with dietary cobalamin deficiency60 and a child with a cobalamin absorption defect.61
Possible Mechanisms
The metabolic profile commonly observed in infants has been attributed to nutritional, developmental, and physiologic factors. The higher MMA levels in breastfed infants in particular may be related to enhanced production of MMA or its precursors by intestinal microorganisms62,63 and formation of MMA from odd-chain fatty acids,64 which are known to be abundant in human milk.65 In addition, low clearance of MMA attributable to immaturity of enzyme or organ systems may predispose infants to high MMA levels.
However, the observation that the period with elevated MMA levels coincides with low serum cobalamin levels, high tHcy levels, and high folate levels, with the latter suggesting a folate-trapping mechanism, supports the possibility of impaired cobalamin status.2 This explanation agrees with our previous observation that markers of cobalamin status in infants are related to infant nutrition and maternal cobalamin status,23 as confirmed for the control group in the present study.
The magnitudes of the observed reductions in tHcy, MMA, and cystathionine levels in response to 1 dose of cobalamin exceed the effects observed in most published intervention studies in adults.66 A meta-analysis of 12 randomized trials of vitamin supplementation to decrease homocysteine levels in adults showed that folic acid reduced homocysteine levels by 25% and cobalamin by an additional 7%.66
Because the enzyme methylmalonyl-CoA mutase is not fully saturated with its cofactor adenosylcobalamin under physiologic conditions, it should be possible to decrease MMA formation through cobalamin supplementation even in the absence of cobalamin deficiency.67 Therefore, a reduction in plasma MMA levels with cobalamin supplementation does not necessarily reflect restoration of cobalamin status. In contrast, methionine synthase, which catalyzes the conversion of homocysteine to methionine, is fully saturated with its cobalamin cofactor under normal conditions and is not stimulated by exogenous cobalamin.68,69 Consequently, a concurrent reduction in tHcy levels with cobalamin supplementation, as seen for the supplement-treated infants, strongly suggests the presence of impaired cobalamin status. This interpretation is supported by the significantly lower serum folate levels in the intervention group, which indicate reversal of the methylfolate trap.
Implications
Our results demonstrate that two thirds of young infants have biochemical evidence of impaired cobalamin status, which responds to cobalamin supplementation. This observation supports the idea that cobalamin deficiency may be common among apparently healthy infants in developed countries2,23 and may not be confined to sporadic cases related to exclusive breastfeeding combined with poor maternal cobalamin status13,15 or to breastfed infants in developing countries.1,4 In our study population, exclusive breastfeeding was common (80% at 6 weeks and 70% at 4 months), which may predispose infants to a negative cobalamin balance. The cobalamin content of milk is reflected by the maternal cobalamin concentration in blood27 and, without exception, reported cases of symptomatic cobalamin deficiency have involved exclusively breastfed infants.12,13,15,70,71
No detailed assessment of developmental status was conducted in the present study, and we observed no relationships between gross growth parameters and infant cobalamin indices. However, the reports on delayed neurodevelopment and long-term neurologic effects related to cobalamin deficiency in young infants demonstrate the importance of adequate cobalamin status during the first months of life.12–19
To optimize compliance, cobalamin was given as an intramuscular injection. One would expect the biochemical response to oral supplements to be equal to the response to parenteral cobalamin administration in this age group, because better cobalamin status was reported for infants fed formula, which provides a greater oral cobalamin supply than breast milk.24,25,53 Our data should strongly encourage advice on cobalamin intake for mothers in the preconceptional, prenatal, and postpartum periods.30,31,71
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CONCLUSIONS |
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Cobalamin supplementation for infants changed all markers of impaired cobalamin status (low cobalamin levels, high tHcy levels, and high MMA levels) toward a profile observed in cobalamin-replete older children and adults. Therefore, high tHcy and MMA levels reported for a large proportion of infants do not reflect organ immaturity but indicate insufficient cobalamin to fully sustain cobalamin-dependent reactions. Clinicians and researchers should address the possible developmental and clinical consequences of this prevalent metabolic evidence of cobalamin deficiency in infants.
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ACKNOWLEDGMENTS |
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The study was supported by grants from the Norwegian Women's Public Health Association, the Norwegian Foundation for Health and Rehabilitation, and the Foundation to Promote Research into Functional Vitamin B12 Deficiency. The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, report writing, or the decision to submit the article for publication.
We thank the staff members at Oasen, Sotra, Olsvik, Varden, and Bønes Helsestasjon, the laboratory staff members of the Department of Pediatrics, Haukeland University Hospital, and all of the mothers and infants who participated in the study.
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FOOTNOTES |
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Address correspondence to Anne-Lise Bjørke-Monsen, MD, PhD, Department of Clinical Biochemistry, Haukeland University Hospital, N-5021 Bergen, Norway. E-mail: almo{at}helse-bergen.no
Financial Disclosure: Dr Ueland reports having received consulting fees from Nycomed and is a member of the steering board of the nonprofit Foundation to Promote Research into Functional Vitamin B12 Deficiency.
This trial has been registered at www.clinicaltrials.gov (identifier NCT00479479).
| What's Known on This Subject Studies suggest that cobalamin deficiency, particularly in breastfed infants, may be prevalent. The prevailing opinion is that the metabolic profile encountered in these infants reflects immature organ systems, rather than impaired cobalamin status.
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| What This Study Adds This intervention trial shows that cobalamin supplementation in 6-week-old infants changes all markers toward the profile observed in cobalamin-replete older children and adults, contradicting the assumption that low cobalamin status in infants is attributable to organ immaturity.
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REFERENCES |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
|---|
1. Allen LH. Vitamin B12 metabolism and status during pregnancy, lactation and infancy. Adv Exp Med Biol.1994; 352 :173 –186[Medline]
2. Rosenblatt DS, Whitehead VM. Cobalamin and folate deficiency: acquired and hereditary disorders in children. Semin Hematol.1999; 36 :19 –34[Web of Science][Medline]
3. Ueland PM, Bjørke-Monsen AL. Total homocysteine is making its way into pediatric laboratory diagnostics. Eur J Clin Invest.2001; 31 (11):928 –930[CrossRef][Web of Science][Medline]
4. Allen LH. Impact of vitamin B-12 deficiency during lactation on maternal and infant health. Adv Exp Med Biol.2002; 503 :57 –67[Web of Science][Medline]
5. Rasmussen SA, Fernhoff PM, Scanlon KS. Vitamin B12 deficiency in children and adolescents. J Pediatr.2001; 138 (1):10 –17[CrossRef][Web of Science][Medline]
6. Jadhav M, Webb JKG, Vaishnava S, Baker SJ. Vitamin B12 deficiency in Indian infants: a clinical syndrome. Lancet.1962; 2 (7262):903 –907[Web of Science][Medline]
7. Allen LH, Rosado JL, Casterline JE, et al. Vitamin B-12 deficiency and malabsorption are highly prevalent in rural Mexican communities.
Am J Clin Nutr.1995; 62
(5):1013
–1019
8. Diez-Ewald M, Torres-Guerra E, Layrisse M, Leets I, Vizcaino G, Arteaga-Vizcaino M. Prevalence of anemia, iron, folic acid and vitamin B12 deficiency in two Bari Indian communities from western Venezuela. Invest Clin.1997; 38 (4):191 –201[Medline]
9. Garewal G, Narang A, Das KC. Infantile tremor syndrome: a vitamin B12 deficiency syndrome in infants.
J Trop Pediatr.1988; 34
(4):174
–178
10. Habicht JP. Expert consultation on the optimal duration of exclusive breastfeeding: the process, recommendations, and challenges for the future. Adv Exp Med Biol.2004; 554 :79 –87[Web of Science][Medline]
11. Kontic-Vucinic O, Sulovic N, Radunovic N. Micronutrients in women's reproductive health, part I: vitamins. Int J Fertil Womens Med.2006; 51 (3):106 –115[Web of Science][Medline]
12. Casella EB, Valente M, de Navarro JM, Kok F. Vitamin B12 deficiency in infancy as a cause of developmental regression. Brain Dev.2005; 27 (8):592 –594[CrossRef][Web of Science][Medline]
13. Cetinkaya F, Yildirmak Y, Kutluk G, Erdem E. Nutritional vitamin B12 deficiency in hospitalized young children. Pediatr Hematol Oncol.2007; 24 (1):15 –21[CrossRef][Web of Science][Medline]
14. Grattan-Smith PJ, Wilcken B, Procopis PG, Wise GA. The neurological syndrome of infantile cobalamin deficiency: developmental regression and involuntary movements. Mov Disord.1997; 12 (1):39 –46[CrossRef][Web of Science][Medline]
15. Kanra G, Cetin M, Unal S, et al. Answer to hypotonia: a simple hemogram.
J Child Neurol.2005; 20
(11):930
–931
16. Wulffraat NM, De Schryver J, Bruin M, Pinxteren-Nagler E, van Dijken PJ. Failure to thrive is an early symptom of the Imerslund-Gräsbeck syndrome. Am J Pediatr Hematol Oncol.1994; 16 (2):177 –180[Web of Science][Medline]
17. Graham SM, Arvela OM, Wise GA. Long-term neurologic consequences of nutritional vitamin B12 deficiency in infants. J Pediatr.1992; 121 (5):710 –714[CrossRef][Web of Science][Medline]
18. von Schenck U, Bender-Gotze C, Koletzko B. Persistence of neurological damage induced by dietary vitamin B-12 deficiency in infancy.
Arch Dis Child.1997; 77
(2):137
–139
19. Louwman MW, van Dusseldorp M, van de Vijver FJ, et al. Signs of impaired cognitive function in adolescents with marginal cobalamin status.
Am J Clin Nutr.2000; 72
(3):762
–769
20. Savage DG, Lindenbaum J, Stabler SP, Allen RH. Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies. Am J Med.1994; 96 (3):239 –246[CrossRef][Web of Science][Medline]
21. Finkelstein JD. Pathways and regulation of homocysteine metabolism in mammals. Semin Thromb Hemost.2000; 26 (3):219 –225[CrossRef][Web of Science][Medline]
22. Stabler SP, Lindenbaum J, Savage DG, Allen RH. Elevation of serum cystathionine levels in patients with cobalamin and folate deficiency.
Blood.1993; 81
(12):3404
–3413
23. Bjørke Monsen AL, Ueland PM, Vollset SE, et al. Determinants of cobalamin status in newborns.
Pediatrics.2001; 108
(3):624
–630
24. Fokkema MR, Woltil HA, van Beusekom CM, Schaafsma A, Dijck-Brouwer DA, Muskiet FA. Plasma total homocysteine increases from day 20 to 40 in breastfed but not formula-fed low-birthweight infants. Acta Paediatr.2002; 91 (5):507 –511[CrossRef][Web of Science][Medline]
25. Minet JC, Bisse E, Aebischer CP, Beil A, Wieland H, Lutschg J. Assessment of vitamin B-12, folate, and vitamin B-6 status and relation to sulfur amino acid metabolism in neonates.
Am J Clin Nutr.2000; 72
(3):751
–757
26. Monsen AL, Refsum H, Markestad T, Ueland PM. Cobalamin status and its biochemical markers methylmalonic acid and homocysteine in different age groups from 4 days to 19 years.
Clin Chem.2003; 49
(12):2067
–2075
27. Specker BL, Black A, Allen L, Morrow F. Vitamin B-12: low milk concentrations are related to low serum concentrations in vegetarian women and to methylmalonic aciduria in their infants.
Am J Clin Nutr.1990; 52
(6):1073
–1076
28. Leonard JV. Stable isotope studies in propionic and methylmalonic acidaemia. Eur J Pediatr.1997; 156 (suppl 1):S67 –S69[CrossRef][Web of Science][Medline]
29. Sniderman LC, Lambert M, Giguere R, et al. Outcome of individuals with low-moderate methylmalonic aciduria detected through a neonatal screening program. J Pediatr.1999; 134 (6):675 –680[CrossRef][Web of Science][Medline]
30. Allen LH. B vitamins: proposed fortification levels for complementary foods for young children.
J Nutr.2003; 133
(9):3000S
–3007S
31. Stabler SP, Allen RH. Vitamin B12 deficiency as a worldwide problem. Annu Rev Nutr.2004; 24 :299 –326[CrossRef][Web of Science][Medline]
32. Worthington-White DA, Behnke M, Gross S. Premature infants require additional folate and vitamin B-12 to reduce the severity of the anemia of prematurity.
Am J Clin Nutr.1994; 60
(6):930
–935
33. Kelleher BP, Broin SD. Microbiological assay for vitamin B12 performed in 96-well microtitre plates.
J Clin Pathol.1991; 44
(7):592
–595
34. O'Broin S, Kelleher B. Microbiological assay on microtitre plates of folate in serum and red cells.
J Clin Pathol.1992; 45
(4):344
–347
35. Windelberg A, Arseth O, Kvalheim G, Ueland PM. Automated assay for the determination of methylmalonic acid, total homocysteine, and related amino acids in human serum or plasma by means of methylchloroformate derivatization and gas chromatography-mass spectrometry.
Clin Chem.2005; 51
(11):2103
–2109
36. Koenker R, Hallock KF. Quantile regression. J Econ Perspect.2001; 15 (4):143 –156[Web of Science]
37. R Development Core Team. R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing;2006
38. Doyle JJ, Langevin AM, Zipursky A. Nutritional vitamin B12 deficiency in infancy: three case reports and a review of the literature. Pediatr Hematol Oncol.1989; 6 (2):161 –172[Web of Science][Medline]
39. Roschitz B, Plecko B, Huemer M, Biebl A, Foerster H, Sperl W. Nutritional infantile vitamin B12 deficiency: pathobiochemical considerations in seven patients.
Arch Dis Child Fetal Neonatal Ed.2005; 90
(3):F281
–F282
40. Weiss R, Fogelman Y, Bennett M. Severe vitamin B12 deficiency in an infant associated with a maternal deficiency and a strict vegetarian diet. J Pediatr Hematol Oncol.2004; 26 (4):270 –271[CrossRef][Web of Science][Medline]
41. American Academy of Pediatrics, Committee on Children With Disabilities. Developmental surveillance and screening of infants and young children.
Pediatrics.2001; 108
(1):192
–196
42. Fréry N, Huel G, Leroy M, et al. Vitamin B12 among parturients and their newborns and its relationship with birthweight. Eur J Obstet Gynecol Reprod Biol.1992; 45 (3):155 –163[CrossRef][Web of Science][Medline]
43. Giugliani ER, Jorge SM, Goncalves AL. Serum vitamin B12 levels in parturients, in the intervillous space of the placenta and in full-term newborns and their interrelationships with folate levels.
Am J Clin Nutr.1985; 41
(2):330
–335
44. Salmenperä L, Perheentupa J, Siimes MA. Folate nutrition is optimal in exclusively breast-fed infants but inadequate in some of their mothers and in formula-fed infants. J Pediatr Gastroenterol Nutr.1986; 5 (2):283 –289[Web of Science][Medline]
45. Smith AM, Picciano MF, Deering RH. Folate intake and blood concentrations of term infants.
Am J Clin Nutr.1985; 41
(3):590
–598
46. Guerra-Shinohara EM, Paiva AA, Rondo PH, Yamasaki K, Terzi CA, D'Almeida V. Relationship between total homocysteine and folate levels in pregnant women and their newborn babies according to maternal serum levels of vitamin B12. BJOG.2002; 109 (7):784 –791[CrossRef][Web of Science][Medline]
47. Molloy AM, Mills JL, McPartlin J, Kirke PN, Scott JM, Daly S. Maternal and fetal plasma homocysteine concentrations at birth: the influence of folate, vitamin B12, and the 5,10-methylenetetrahydrofolate reductase 677C
T variant.
Am J Obstet Gynecol.2002; 186
(3):499
–503[CrossRef][Web of Science][Medline]
48. Bates CJ, Mansoor MA, Gregory J, Pentiev K, Prentice A. Correlates of plasma homocysteine, cysteine and cysteinyl-glycine in respondents in the British National Diet and Nutrition Survey of young people aged 4–18 years, and a comparison with the survey of people aged 65 years and over. Br J Nutr.2002; 87 (1):71 –79[CrossRef][Web of Science][Medline]
49. De Laet C, Wautrecht JC, Brasseur D, et al. Plasma homocysteine concentration in a Belgian school-age population.
Am J Clin Nutr.1999; 69
(5):968
–972
50. Delvin EE, Rozen R, Merouani A, Genest J Jr, Lambert M. Influence of methylenetetrahydrofolate reductase genotype, age, vitamin B-12, and folate status on plasma homocysteine in children.
Am J Clin Nutr.2000; 72
(6):1469
–1473
51. Vilaseca MA, Moyano D, Ferrer I, Artuch R. Total homocysteine in pediatric patients.
Clin Chem.1997; 43
(4):690
–692
52. Bolann BJ, Solli JD, Schneede J, et al. Evaluation of indicators of cobalamin deficiency defined as cobalamin-induced reduction in increased serum methylmalonic acid.
Clin Chem.2000; 46
(11):1744
–1750
53. Specker BL, Brazerol W, Ho ML, Norman EJ. Urinary methylmalonic acid excretion in infants fed formula or human milk.
Am J Clin Nutr.1990; 51
(2):209
–211
54. Specker BL, Miller D, Norman EJ, Greene H, Hayes KC. Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and an identification of an acceptable source of vitamin B12.
Am J Clin Nutr.1988; 47
(1):89
–92
55. Obeid R, Munz W, Jager M, Schmidt W, Herrmann W. Biochemical indexes of the B vitamins in cord serum are predicted by maternal B vitamin status.
Am J Clin Nutr.2005; 82
(1):133
–139
56. Ford C, Rendle M, Tracy M, Richardson V. Vitamin B-12 levels in human milk during the first nine months of lactation. Int J Vitam Nutr Res.1996; 66 (4):329 –331[Web of Science][Medline]
57. Allen RH, Stabler SP, Savage DG, Lindenbaum J. Metabolic abnormalities in cobalamin (vitamin B12) and folate deficiency. FASEB J.1993; 7 (14):1344 –1353[Abstract]
58. Das KC, Herbert V. Vitamin B12-folate interrelations. Clin Haematol.1976; 5 (3):697 –745[Web of Science][Medline]
59. Bleie O, Refsum H, Ueland PM, et al. Changes in basal and postmethionine load concentrations of total homocysteine and cystathionine after B vitamin intervention.
Am J Clin Nutr.2004; 80
(3):641
–648
60. Higginbottom MC, Sweetman L, Nyhan WL. A syndrome of methylmalonic aciduria, homocystinuria, megaloblastic anemia and neurological abnormalities in a vitamin B12-deficient breastfed infant of a strict vegetarian. N Engl J Med.1978; 299 (7):317 –323[Abstract]
61. Hollowell JG Jr, Hall WK, Coryell ME, McPherson J Jr, Hahn DA. Homocystinuria and organic aciduria in a patient with vitamin-B12 deficiency. Lancet.1969; 2 (7635):1428[Medline]
62. Bain MD, Jones M, Borriello SP, et al. Contribution of gut bacterial metabolism to human metabolic disease. Lancet.1988; 1 (8594):1078 –1079[Web of Science][Medline]
63. Thompson GN, Chalmers RA, Walter JH, et al. The use of metronidazole in management of methylmalonic and propionic acidaemias. Eur J Pediatr.1990; 149 (11):792 –796[CrossRef][Web of Science][Medline]
64. Thompson GN, Walter JH, Bresson JL, et al. Sources of propionate in inborn errors of propionate metabolism. Metabolism.1990; 39 (11):1133 –1137[CrossRef][Web of Science][Medline]
65. Koletzko B, Mrotzek M, Bremer HJ. Fatty acid composition of mature human milk in Germany.
Am J Clin Nutr.1988; 47
(6):954
–959
66. Clarke R, Armitage J. Vitamin supplements and cardiovascular risk: review of the randomized trials of homocysteine-lowering vitamin supplements. Semin Thromb Hemost.2000; 26 (3):341 –348[CrossRef][Web of Science][Medline]
67. Willard HF, Rosenberg LE. Inborn errors of cobalamin metabolism: effect of cobalamin supplementation in culture on methylmalonyl CoA mutase activity in normal and mutant human fibroblasts. Biochem Genet.1979; 17 (1–2):57 –75[CrossRef][Web of Science][Medline]
68. Chen Z, Chakraborty S, Banerjee R. Demonstration that mammalian methionine synthases are predominantly cobalamin-loaded.
J Biol Chem.1995; 270
(33):19246
–19249
69. Taylor RT, Hanna ML, Hutton JJ. 5-Methyltetrahydrofolate homocysteine cobalamin methyltransferase in human bone marrow and its relationship to pernicious anemia. Arch Biochem Biophys.1974; 165 (2):787 –795[CrossRef][Web of Science][Medline]
70. Baatenburg de Jong R, Bekhof J, Roorda R, Zwart P. Severe nutritional vitamin deficiency in a breast-fed infant of a vegan mother. Eur J Pediatr.2005; 164 (4):259 –260[CrossRef][Web of Science][Medline]
71. Katar S, Nuri Ozbek M, Yaramis A, Ecer S. Nutritional megaloblastic anemia in young Turkish children is associated with vitamin B-12 deficiency and psychomotor retardation. J Pediatr Hematol Oncol.2006; 28 (9):559 –562[CrossRef][Web of Science][Medline]
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