Zinc concentration of breast milk and its diurnal variation in Bangladeshi mothers.

Deficient dietary zinc intake has been associated with diminished growth velocity. Until the age of 4-6 months milk is the only dietary source of zinc for most infants. This study investigated the zinc content of mature breast milk of low-income Bangladeshi mothers. Enrolled were 34 exclusively breast-feeding mothers of low socioeconomic status in the 6th-36th week of lactation who submitted 3 samples of breast milk at different times (5-7 a.m. 2-3 p.m. and 10 p.m.) within a single day. Two-thirds of these mothers had a body mass index less than 20. Only 20.5% of the 102 total milk samples contained at least 3 mcg/ml of zinc the recommended daily intake. The range was 0.17-4.38 mcg/ml. The average zinc content was 2.10 mcg/ml in the early morning 1.74 mcg/ml at mid-afternoon and 1.84 mcg/ml at late evening. There were significant differences between the morning and mid-afternoon samples. Breast milks zinc content was not associated with maternal age parity maternal body mass index or age of the child. The low zinc content of breast milk identified in this study raises serious concerns about the growth and development of the children of low-income women in Bangladesh and other developing countries.