Abstract
Background: Vitamin B12 deficiency is associated with increased plasma methylmalonic acid (MMA) and/or homocysteine. The principal cause of vitamin B12 deficiency in infants is impaired maternal vitamin B12 status. Recent studies suggest increased plasma MMA and homocysteine during infancy is common although the cause and significance are unclear.
Aims: To determine the normal range of plasma MMA in infants during the first months of life and to correlate this with other biochemical and dietary markers of vitamin B12 status. We also aimed to determine if breast-fed infants had higher plasma MMA than formula-fed infants.
Methods: A prospective cohort study was conducted to measure biochemical markers of vitamin B12 status in normal infants and their mothers. One hundred and one infant-mother pairs had blood samples taken when the infants were 4 and 10 weeks of age for measurement of plasma vitamin B12, red cell folate, plasma MMA and homocysteine. Maternal dietary intake of vitamin B12 was calculated using a validated food frequency questionnaire. Statistical analyses were conducted using SPSS statistical software.
Results: The range of plasma MMA for all infants was 0.09–18.43 μmol/L (median 0.40, interquartile range 0.23–0.89 μmol/L). At 10 weeks of age, 46% of breast-fed and 21% of formula-fed infants had plasma MMA greater than 0.50 μmol/L (p=0.016). Breast-fed infants had lower plasma vitamin B12 (p<0.01) and red cell folate (p<0.01), and higher plasma homocysteine (p=0.02) than formula-fed infants. In breast-fed infants, plasma MMA and vitamin B12 strongly correlated with maternal plasma MMA and vitamin B12. This correlation was not seen in formula-fed infants. Breast-fed infants also showed a strong relationship between plasma homocysteine and vitamin B12 and MMA. The relationship between infant vitamin B12 status and maternal dietary intake will be presented.
Conclusion: The normal range for plasma MMA in young infants is considerably higher than for older children and adults. Breast-fed infants have higher plasma MMA and homocysteine, and lower vitamin B12 and red cell folate than formula-fed infants. Due to the strong correlation between infant and maternal vitamin B12 status in breast-fed infants, these findings may indicate sub-optimal vitamin B12 status in breastfeeding mothers. Further analysis of dietary data will help to elucidate the cause of these findings. The clinical significance remains to be established in future studies.
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Simmer, K., Colvin, J., Lewis, B. et al. 240 Determinants of Vitamin B12 Status in Infants. Pediatr Res 56, 504 (2004). https://doi.org/10.1203/00006450-200409000-00263
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DOI: https://doi.org/10.1203/00006450-200409000-00263