SummaryThe concentration of total carnitine in human breast milk remained at a constant mean level near 62.9 range: 56.0-69.8/ nmoles/ml during the first 21 days postpartum. The carnitine level fell significantly to 35.2 + 1.26 nmoles/ml until the 40-50th day.The carnitine concentrations did not depend on the secreted volume of milk. In comparison, fresh and commercial pasteurized cow's milk contained 206.2 (range: 192-269) nmoles/ml and 160.0 (range: 158-200) nmoles/ml carnitine, respectively. In the sera of nursing mothers, the concentration of total carnitine was lower on the first day after delivery (27.2 + 1.19 nmoles/ml) but returned to normal by the 21st day postpartum (38.8 & 2.97 nmoles/ml). SpeculationRecently it has been reported that human and animal newborns need exogenous carnitine (lo), which probably plays an important role in neonatal ketogenesis. The natural carnitine source for newborns is the mother's milk. Determining the relationship between days postpartum and carnitine concentration in breast milk makes possible an estimate of when the mother's milk is the optimal carnitine source.In mammals the primary fuel for the fetus is maternal glucose. Immediately after birth, newborns must switch over to combustion 3f fat released from the adipose tissue (9) or derived from the mother's milk (4). As a consequence, the level of nonesterified fatty acids and ketone bodies rise rapidly in the newborn serum (8,12,13). Ketone bodies produced by the liver serve as important fuel for extrahepatic tissues and as precursors for brain lipid synthesis (14). Carnitine, y-trimethylamino-P-hydroxybutyrate, and carnitine palrnitoyltransferase enzyme (CPT) EC 2.3.1.21 play a key role in fatty acid oxidation (3). They transport the activated fatty acids from the cytoplasm across the inner mitochondria1 membrane barrier to the site of combustion. The hepatic carnitine level in rats (6) and both the carnitine level and CPT activity in developing rats (2, 12) correlate well with the ketogenic capacity of the liver. However, newborn rats (12) and\human neonates (10) need exogenous carnitine supplement. Mother's milk is the most common carnitine source for babies. In rats, carnitine is shown to be transferred from the maternal liver to the neonatal tissues via milk of the mother animal (12). Human breast milk also contains carnitine in the range of 39-63 nmoles/ml (10). In rats, milk carnitine levels after birth sharply decrease within 10 days. This decrease is accompanied by a-decline in hepatic carnitine and serum ketone body concentration in the baby rats (12). The question arises whether or not the carnitine level in human breast milk decreases just as quickly.The present study follows carnitine levels in human breast milk during the period after delivery. MATERIALS AND METHODSTwenty-seven mothers delivering at term without any complication were involved in the investigations. The phrase, the 1st day refers to the day immediately after delivery. Milk samples of about 2 ml were collected directly from the mothers by...

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