Nutrition Maternelle et Pédiatrique
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Breast Milk Iron Concentrations may be Lower than Previously Reported: Implications for Exclusively Breastfed Infants

Cai C, Harding SV, Friel JK

Objective: Atomic Absorption Spectrophotometry (AAS) is the most common technique for detecting iron in human milk. Quantifying the iron in human milk is essential for determining the amount of dietary iron available to the exclusively breastfed infant. To determine whether more sensitive procedures for iron analyses would yield different values than those obtained using the AAS, flame atomic absorption, we investigated and compared three different analytical techniques using AAS. Methods: The present experiment was conducted as part of a larger study on the iron supplementation of 77 exclusively breast-fed infants. Breastmilk samples were collected from 10 mothers of full-term infants at one and 3½ months of age. Each sample was analyzed with a Perkin-Elmer 2380 Atomic Absorption Spectrophotometer by the following analytical methods: flame atomic absorption spectrophotometry (FAAS), direct sample analysis with graphite furnace atomic absorption spectrophotometry (GFAAS) and the method-of-standard-additions with GFAAS. Results: While all values were within reported ranges, there was significant inter-method variability. The decrease in iron concentration between 1-month and 3.5-month milk samples found in the present study is in agreement with a previous report. GFAAS methods produced consistently lower values than did FAAS: 1 month: direct GFAAS, 0.50 (0.33-0.86) μg/ml; method-of-addition GFAAS, 0.45 (0.31-0.66) μg/ml; FAAS 0.76 (0.25-1.60 μg/ml), mean (range): 3.5-month: direct GFAAS, 0.29 (0.13-0.46 μg/ml; method-of-addition GFAAS, 0.29 (0.11-0.44 μg/ml); FAAS method 0.78 (0.19-1.64) μg/ml. There was no difference between the two GFAAS methods at either time point. Conclusion: The findings obtained from this study suggest that much of the variability seen in the reported values of human milk iron concentrations could be due to the use of different analytical procedures. GFAAS results are consistently lower than those determined by FAAS suggesting that the exclusively breastfed infant consumes less iron than previously thought.