Concentrations of Nε-carboxymethyllysine in human breast milk, infant formulas, and urine of infants

Maillard products, such as N-carboxymethyllysine (CML), are readily formed during the manufacturing of infant formulas. Little has been known, however, about the presence of CML in human breast milk and about the uptake of CML by infants. In this study, CML was measured in the serum and breast milk of 32 healthy mothers by ELISA. CML concentrations in breast milk (137 +/- 82.7 ng/mL) were significantly lower than in the serum (399 +/- 67.8 ng/ mL, p < 0.001) and on average 35-fold lower than in infant formulas (4754 +/- 4299.5 ng/ mL). CML was also measured in the urine of 21 infants, which were fed with breast milk or formulas. Although there was a tendency toward higher urinary CML excretion in infants fed with hypoallergenic formulas compared to breast-fed ones, the differences were not significant. Neonates that were delivered by vaginal birth had significantly higher concentrations of CML compared to those delivered by caesarean section (1306 +/- 653 vs 601 +/- 220 ng/ mL, p = 0.012). It is conclued that CML passes from the serum into the breast milk, but the levels are by far lower than in infant formulas. In very young neonates (<= 3 days), the mode of delivery has a greater influence on urinary CML excretion than the nutrition.