Discussion
nonbreastfed
FOLATE DEFICIENCY, VITAMIN B12 DEFICIENCY
In this study of healthy pregnant females and their infants from Norway, we found that a considerable number of infants had low vitamin B12 status at 3 and 6 mo of age, but sufficient folate status. The pregnant females had sufficient vitamin B12 status during pregnancy, but a high proportion had folate deficiency at the end of pregnancy. We also found an association between maternal vitamin B12 status during pregnancy and infant vitamin B12 status at 3 and 6 mo of age. Additionally, the study indicated that breastfed infants had lower vitamin B12 status compared with nonbreastfed infants, and B-vitamin supplement use during pregnancy was associated with better vitamin B12 status among infants during the first 6 mo of life.In the current study, more than half of the infants had elevated plasma t-Hcy concentrations at 3 and 6 mo. t-Hcy is the preferred marker of vitamin B12 status in the first 2 y of life, but it increases with both vitamin B12 and folate deficiency [Similar to the high prevalence of subclinical vitamin B12 deficiency, defined as t-Hcy concentrations >6.5 μmol/L in our study, our results suggest the infants also had low vitamin B12 status according to the combined indicator of vitamin B12 status, cB12, where a total of 47% of infants had a low vitamin B12 status at 3 mo, which further increased to 60% at 6 mo. Despite the utility of cB12, taking more than one biomarker of vitamin B12 into account when assessing vitamin B12 status, it is important to note that the use of cB12 as a marker of vitamin B12 status has not yet been validated for use in infancy. Therefore, further studies evaluating the use of the combined indicator in infant populations are necessary. Nonetheless, taking our infant vitamin B12 status observations together with the findings of previous studies suggests that a high proportion of Norwegian infants have biochemical signs of subclinical vitamin B12 deficiency.Few of the mothers had poor vitamin B12 status during pregnancy, but maternal vitamin B12 status at GW 18 and 36 were moderately associated with infants’ vitamin B12 status at 3 and 6 mo of age. These results are in line with previous studies showing that maternal vitamin B12 status during pregnancy is associated with infant vitamin B12 status from birth until 2 y of age [Maternal folate status during pregnancy was not associated with infants’ folate status at 3 and 6 mo of age. Similarly, Hay et al. [We found that the t-Hcy in breastfed infants was 44% (4%–100%) higher compared with that of the nonbreastfed infants at age 3 mo, increasing to 55% (30%–85%) higher at age 6 mo. Previous studies among Norwegian and Danish infants also concluded that breastfed infants had lower vitamin B12 status compared with nonbreastfed infants at 6 mo to 2 y of age [Overall, maternal B-vitamin supplement use during pregnancy was not clearly associated with vitamin B12 status in infancy. Exceptions were maternal supplement use at GW 18, which was associated with a 33% (9%–63%) increase in infant cobalamin concentrations at 3 mo of age and an 15% (1%–27%) decrease in t-Hcy concentrations at 6 mo of age. Further, supplement use in GW 36 was associated with an 20% (1%–44%) increase in infant cobalamin concentrations at 6 mo of age. Previous studies have shown conflicting results regarding maternal supplement use [A strength of our study is the use of both direct and functional biomarkers when assessing vitamin B12 status, as is recommended [A major limitation of our study is the cutoff used to define low vitamin B12 status in our participants. There is a lack of consensus regarding the reference values to define deficiency and subclinical deficiency for vitamin B12 and folate, and most of the indicators do not have age-specific cutoffs or cutoffs for pregnant females. Some randomized controlled trials have investigated if supplementing infants with vitamin B12 improves cognitive development [In conclusion, we found a high prevalence of subclinical vitamin B12 deficiency in the infants in our study but adequate folate status. Infant’s vitamin B12 status was associated with mother’s status during pregnancy and breastfeeding. Further studies are needed to investigate if this observed subclinical vitamin B12 deficiency has clinical implications for the infants, or if this reflects the need to develop specific cutoffs used to define overt and subclinical vitamin B12 deficiency during infancy.