Plasma total homocysteine increases from day 20 to 40 in breastfed but not formula-fed low-birthweight infants.

Homocysteine is an intermediate in the folate cycle and methionine metabolism. This study investigated whether formula-fed infants have different plasma total homocysteine to their breastfed counterparts, and during what period any difference developed. Plasma total homocysteine was determined in 53 formula-fed and 15 breastfed healthy low-birthweight babies (< or = 2500 g) around days 10, 20 and 40. Total homocysteine was also measured in human milk. Mean +/- SD plasma total homocysteine levels (micromol l(-1)) at days 10, 20 and 40 were 6.4 +/- 2.6, 6.7 +/- 2.4 and 9.1 +/- 2.4 (breastfed), and 7.5 +/- 3.2, 7.3 +/- 2.1 and 7.4 +/- 1.6 (formula-fed). Homocysteine of breastfed babies at day 40 was higher than that of breastfed babies at day 20 (p < 0.0001), and that of formula-fed counterparts at day 40 (p = 0.002). Homocysteine correlated negatively with formula (day 10) and breast milk (day 40) volume intakes. Median (range) homocysteine in 12 mature human milk samples was 0.30 (not detectable to 0.7) micromol l(-1).Increasing plasma total homocysteine in breastfed babies to higher levels compared with formula-fed babies may be caused by a gradually developing suboptimal B-vitamin status in lactating women.