Hj. Kalkwarf et M. Kalis, URINARY LACTOSE - CHANGES POSTPARTUM AND RELATION WITH BREAST-MILK PRODUCTION, The American journal of clinical nutrition, 65(3), 1997, pp. 744-749
Measurement of milk intake by breast-fed infants is difficult and a si
mple measure would be helpful for research and clinical practice. Mate
rnal urinary lactose excretion has been proposed as a simple measure o
f lactation performance. The objectives of this study were to describe
the pattern of urinary lactose excretion postpartum, and to determine
whether lactose excretion could predict breast milk output. Lactose e
xcretion was determined in 50 lactating and 49 nonlactating women at 0
.5, 3, and 6 mo postpartum, and in 29 weaning women and 30 nonlactatin
g women at 5, 8, and 11 mo postpartum. Lactose excretion was 4- to 17-
fold higher in lactating than in nonlactating women, depending on the
time point studied, and was highest in both groups 0.5 mo postpartum.
Lactose excretion decreased after weaning but remained higher than in
nonlactating women 1.3 mo after weaning was completed. Sixty-two addit
ional women between 1.5 and 12 mo postpartum were studied to determine
the ability of urinary lactose to predict milk output. There was a po
sitive association between milk output and urinary lactose excretion,
with correlation coefficients ranging from 0.17 to 0.30 depending on t
he measurement interval for lactose excretion. Lactose excretion could
explain 2-9% of the variance in milk output, and could correctly clas
sify 29-40% of individuals into tertiles of milk output. Although urin
ary lactose excretion reflects changes in biological activity of the m
ammary gland and gross changes in milk production, it is not a precise
predictor of milk output.