Dietary carnitine effects on carnitine concentrations in urine and milk in lactating women

The effect of dietary carnitine on urinary excretion of free and total carnitine and on breast-milk secretion of the carnitine fractions in 15 control and 16 lactating women aged 21-40 y was measured. Free and total carnitine excretions, obtained from 24-h urine collections, correlated with carnitine consumed on the collection day (P less than 0.03, P less than 0.01, respectively) but not with the mean intake calculated from 3-d diet records. The immediate responses of the control and lactating groups were not significantly different. Urinary excretion of carnitine (n = 31) was 82 +/- 13 mumol/d for free excretion and 226 +/- 22 mumol/d for total excretion. Milk free, acid-soluble acyl-, acid-insoluble acyl-, or total carnitine did not correlate with dietary carnitine or with the duration of lactation (1-10 mo). Milk total carnitine was 45 +/- 3 mumol/L. With the carnitine content of breast milk remaining stable for greater than or equal to 10 mo, the importance of exogenous carnitine throughout infancy is suggested.