Vitamin B-12 deficiency is very prevalent in lactating Guatemalan women and their infants at three months postpartum.

Vitamin B-12 status was evaluated in 113 Guatemalan women and their infants at 3 mo of lactation. Plasma vitamin B-12 was deficient or low in 46.7% of the mothers, and holotranscobalamin II (holo TC II) concentrations were low in 32.3%, which may indicate vitamin B-12 malabsorption. Only 9% had deficient or low plasma folate. Breast milk vitamin B-12 was low in 31%, and negatively correlated with infant urinary methylmalonic acid (UMMA, r = -0.22, P < 0.05, n = 88); UMMA was elevated in 12.2% of the infants, indicating vitamin B-12 deficiency. Mothers of the infants with elevated UMMA had significantly lower concentrations of vitamin B-12 in their breast milk compared with mothers of infants with normal UMMA concentrations (410.7 +/- 247.7 vs. 705.3 +/- 487.5 pmol/L, P = 0.05, n = 87). Mean maternal dietary intake of vitamin B-12 was significantly correlated with plasma vitamin B-12 (r = 0.20, P = 0. 05, n = 94) and was the main determinant of plasma vitamin B-12 in a linear regression model. Determinants of maternal holo TC II concentrations included dietary intake of vitamin B-12 and Giardia lamblia infection. There were no statistically significant determinants of infant UMMA concentrations. We conclude that vitamin B-12 deficiency is highly prevalent in these lactating women and is associated with depletion of the vitamin in their infants. The cause of the maternal deficiency is unknown, but malabsorption exacerbated by low dietary intake of the vitamin is a possibility.