Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2005
Publication Date: 9/21/2005
Citation: Hunt, C., Butte, N.F., Johnson, L.K. 2005. Boron concentrations in milk from mothers of exclusively breast-fed healthy full-term infants are stable during the first four months of lactation. Journal of Nutrition. 135:2383-86. Interpretive Summary: Boron is a natural bioactive element that has many of the characteristics of an element required by the human body. Therefore, it is important to establish whether boron is present in human breast milk and whether the body controls the amount of boron in milk. Lactating mothers of healthy full-term infants living in Houston, TX, agreed to collect breast milk samples once a month for 4 months. We analyzed the samples for boron and other trace elements known to be essential (calcium, magnesium, and zinc). We found that boron concentrations were stable in full term milk during the first 4 months of lactation. As expected, there was a reduction in the concentrations of calcium and zinc and an increase in magnesium over time. The stable concentration of boron in milk over time suggests that the element is under control and in a manner similar to that established earlier for calcium. In this respect, boron metabolism in milk differs from that of copper or magnesium, elements whose concentrations decrease or increase respectively over time. Further research is needed to find out how the human body maintains the amount of boron in breast milk.
Technical Abstract: Because boron is a bioactive element that satisfies several of the criteria for essentiality in humans, the aim of the present work was to determine the profile of boron metabolism in human milk during the first 4 mo of lactation. The concentration of boron and other minerals was determined in archived milk collected (1980-84) once a month for 4 months from lactating mothers of full-term, exclusively breast-fed, infants living in Houston, TX. A linear model (treating month as a continuous variable) indicated that B concentrations were stable between month 1 and 4 (42 to 35 ug/L milk, x ± SEM, p = 0.14). Mg concentrations increased slightly over time (28.6 to 33.0 mg/L, p < 0.0001) while Ca concentrations decreased slightly (280 to 269 ug/g milk, p < 0.02) and Zn decreased substantially (2.6 to 1.3 ug/g milk, p < 0.0001). Similarities in findings reported here and earlier (from samples collected in St. John's, Newfoundland) provides further evidence that boron is metabolically regulated. Because dietary boron is variable and highly bioavailable, future investigations of boron regulatory mechanisms should focus on metabolism of bone (major storage site of B) and kidney excretion (major excretory route for B).