Vitamin B-12 Deficiency Among Breastfed Infants
by Anne Eglash MD, IBCLC, FABM
Parental and infant vitamin B-12 deficiency during lactation has been well documented. When should we suspect this?
Authors for this week's article shared data that 10% of infants in Norway have been found to be vitamin B12 deficient. The authors were interested in identifying risk factors for vitamin B12 deficiency in exclusively breastfed infants and describing presenting symptoms.
They reviewed 2 hospital medical record databases in Norway and identified 85 dyads with infants born in 2011-2018 who were under 1 year of age and treated for B-12 deficiency. They compared data to a control group of 252 healthy dyads aged 3-7 months, who were born in 2018-2019.
80% of the infants with vitamin B-12 deficiency demonstrated symptoms within the first 2 months of life. The most common neurologic symptoms were 'spells', which included apnea, absences or motor seizures. Other less common symptoms were hypotonia, excessive sleepiness, failure to thrive, and neutropenia (low white cell count).
- The most common reason for low vitamin B12 in the subject population was a maternal vegetarian or vegan diet.
- Mothers who took a vitamin supplement with B12 during pregnancy were less likely to have an infant with B-12 deficiency.
- Nitrous oxide given to mothers during labor was a risk factor for early infant vitamin B12 deficiency.
- Among the mothers with infants who had low B12 levels, all had low B-12 levels themselves.
- Among the mothers with infants who had low B12 levels, 7% were diagnosed with celiac disease.
See the Answer
In Norway, 5-10% of neonates and infants have biomarkers suggesting vitamin B12 deficiency from newborn screening tests and unselected clinical screening, respectively.
The aims were to identify risk factors and describe presenting symptoms and biochemical profiles in infants diagnosed with vitamin B12 deficiency.
In this case-control study, we searched hospital medical records for infants younger than one year born in 2011-2018, diagnosed with vitamin B12 deficiency. We compared 85 cases with a control group of 252 infants aged 3-7 months. Parents completed questionnaires.
Of the 85 cases with vitamin B12 deficiency, 80% presented with spells (37%) of apneas, motor seizures, or absences within the first two months of life. Tremor (29%) and irritability (18%) were the most common findings at the first examination. Serum total homocysteine ≥10 μmol/L was found in 77% of cases compared to 28% of controls (P < 0.001). None of the mothers were vegetarians, but 25% reported a previous history of vitamin B12 deficiency and 7% had celiac disease. The dose of nitrous oxide given during labor was significantly associated with infant serum total homocysteine level at diagnosis (r = 0.37, 95% confidence interval = 0.16-0.55, P < 0.001) for cases, but not for controls.
Spells, tremor, and irritability are common findings in early infant vitamin B12 deficiency. Nitrous oxide given during labor is proposed as a contributing risk factor to the development of early infant vitamin B12 deficiency.
None of the mothers in this population whose infants had vitamin B-12 deficiency were vegans or vegetarians.
The authors stated that total homocysteine is a preferred biochemical marker of infant B-12 status, with a level <6.5µmol/L considered normal at 4 months of age. An elevated total homocysteine is associated with vitamin B12 deficiency.
The dose of nitrous oxide administration during labor correlated with infant serum total homocysteine, and there is evidence that nitrous oxide interferes with vitamin B12 metabolism.
The authors made the point that in studies among other populations, vegan or vegetarian diets were responsible for vitamin B12 deficiency. However, in Norway, where vegan and vegetarian diets are less common, infant vitamin B-12 deficiency should still be suspected among infants who present with early neurologic symptoms, failure to thrive, or excessive sleepiness.