Vitamin B‐12 content of human milk: predictors and relationship to infant and maternal indicators of B‐12 status

Although adequate B‐12 status is critical for normal infant development, in populations with low animal product intake maternal B‐12 depletion is common and there are few data on adequacy of breast milk B‐12. In peri‐urban Guatemala City, we reported a 36% prevalence of B‐12 depletion/deficiency (serum B12 <221 pmol/mL) in lactating women, and 30% in their infants, at 12 months post‐partum. Breast milk from 183 mothers was frozen and analyzed for vitamin B‐12 at UC Davis using modified papain digestion. Median B‐12 content was 394 (98–1408) pmol/mL. Maternal and infant serum B‐12 were correlated (r=0.26, P<0.001), and breast milk B‐12 was correlated with B‐12 in maternal (r=0.22, P<0.004) and infant (r=0.24, P<0.001) serum. Maternal serum (r=0.15, P<0.02) and milk (r=0.21, P<0.002) B‐12 were correlated with B‐12 intake from maternal diet. Infant B‐12 intake from complementary foods was a positive predictor, and from breast milk a negative predictor, of infant serum B‐12; by 12 mo of age complementary feeding predicts infant B‐12 status more strongly than breast milk. To test the amount of supplemental B‐12 needed to increase levels in breast milk and improve infant status, 18 mothers with serum B‐12 74–221 pmol/mL at 2 mo postpartum were provided 3, 100, 250, 500 or 1000 μg/d orally for 2 mo. 500 μg/d for 2 mo (20 times the RDA) was needed to increase maternal serum B‐12 by 145 pmol/mL, milk B‐12 by 203 pmol/mL and infant serum B‐12 by 138 pmol/mL to adequate levels.