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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #75418
Title: ABSORPTION OF CALCIUM, ZINC AND IRON FROM BREAST MILK BY 5- AND 7-MONTH- OLD INFANTS

Author
item Abrams, Steven
item WEN, JIANPING - BAYLOR COLL OF MEDICINE
item STUFF, JANICE - BAYLOR COLL OF MEDICINE

Submitted to: Pediatric Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Doctors generally recommend that for optimal nutrition and immune protection, babies should be breast-fed throughout the first year of life, with solid foods introduced between 4 to 6 months of age. However, no one has known whether the addition of solid food interferes with the babies' ability to absorb important minerals from breast milk. We set up a study to determine this. We used an innovative multiple-tracer method to measure iron, calcium and zinc absorption in 5- to 7-month-old infants, most of whom had started eating solid food. This method has never been used before to measure calcium and zinc absorption in healthy, full-term infants. We found that minerals are well absorbed from human milk in older infants after they are started on solid food. We also demonstrated that this special technique works well with this age group. These results provide extremely useful, new information about human nutrition.

Technical Abstract: Data are scarce regarding mineral bioavailability from human milk in older infants who may also be receiving solid foods (beikost). We measured the absorption of Ca, Zn and Fe in 14 healthy, non-anemic 5- to 7-month-old breast-fed infants whose mothers' milk was extrinsically labeled with stable isotopes (44Ca, 70Zn, 58Fe)of these minerals. In addition, Ca and Zn stable isotopes (46Ca and 67Zn) were administered intravenously and a second isotope of Fe (57Fe) was given orally without food as a reference dose. Subjects were not receiving any artificial infant formula or cow milk, but most (10/14) were receiving beikost. Ca and Zn absorption was calculated using the urinary excretion of the isotopes during the 24-h after dosing (Ca) or their urinary ratio 72-h after dosing (Zn). Fe absorption was calculated using the RBC incorporation at 14 d. Fe absorption averaged 20.7 +/- 14.8% from the 58Fe given with human milk (geometric mean, 14.8%) and 17.7 +/- 15.1% (geometric mean, 11.0%) from th 57Fe reference dose. Ca absorption averaged 61.3 +/- 22.7% and Zinc absorption (n=10) averaged 49.5 +/- 18.5%. Absorption of Fe (natural logarithm) from the reference Fe dose (57Fe) but not from the human milk (58Fe) was significantly negatively correlated to serum ferritin (r= -0.70, p=0.007 vs. r= -0.35, p=0.24). Total daily Fe, Ca and Zn intakes from beikost was significantly negatively correlated to absorption of Fe from the reference dose (r= -0.61, p=0.021). We conclude that minerals are well absorbed from human milk in older infants after the introduction of beikost to the diet.