Are breast-fed infants vitamin K deficient?

Abstract

Hemorrhagic disease of the newborn is a disease of breast-fed infants. We have followed 119 exclusively breast-fed infants for up to 6 months of age, who received 1 mg of vitamin K1 intramuscularly at birth. As vitamin K is undetectable in cord blood, the only other source in breast-fed infants is human milk. We found persistently low vitamin K1 plasma concentrations in these infants by 4 weeks, and vitamin K concentrations at 2, 4, 6, 8, 12, and 26 weeks averaged 1.18 ± 0.99, 0.50 ± 0.70, 0.16 ± 0.07, 0.20 ± 0.20, 0.25 ± 0.34, and 0.24 ± 0.23 ng/mL, respectively (lower limit of adult normal = 0.5 ng/mL). Vitamin K1 in breast milk at 2, 6, 12, and 26 weeks was also very low, averaging 1.17 ± 0.70, 0.95 ± 0.50, 1.15 ± 0.62, and 0.87 ± 0.50 mg/mL, respectively. This may be secondary to low maternal vitamin K1 intakes or inability of vitamin K1 to penetrate human milk. We had previously reported a relatively high mean vitamin K intake of 316 ± 548 μg in 20 lactating women during the first 6 months of lactation (mean of 60, 3-day dietary recalls) which greatly exceeded the recommended daily allowance of 1 μg/kg/day. The vitamin K content of foods was recently revised downward utilizing newer analytical methods (Booth et al. 1995). Recalculating maternal vitamin K intakes in this original cohort resulted in a dramatic decrease in intake to 74 ± 57 μg/day, an amount closely approximating 1 μg/kg/day. We have completed 69 new dietary recalls in 23 lactating women and, combining these data with the previous study, determined a maternal vitamin K1 mean intake of 65 ± 48 μg/day (0.8-1.3 μg/kg/day). Other than plasma vitamin K1 concentrations, PIVKA (undercarboxylated prothrombin produced in the absence of vitamin K) is a marker of vitamin K deficiency. We measured PIVKA in 156 cord bloods of full-term infants. Seventy-five (48%) had a significantly elevated PIVKA (>0.1 absorption units per milliliter). Seventy-seven of these infants who were exclusively breast-fed subsequently had no detectable PIVKA at 4 weeks, but by 8 weeks, 3 were again positive for PIVKA (prothrombin times were normal). Breast-fed infants may benefit from increased maternal vitamin K intakes (>1 μg/kg/day) during pregnancy and lactation. A supplement of 5 mg of vitamin K to lactating mothers will increase the concentration in human milk to 80.0 ± 37.7 ng/mL and significantly increase infant plasma vitamin K (Greer et al. 1997).