Lactoferrin binds iron ions and the presence of a lactoferrin receptor in the small intestine suggests iron bound to lactoferrin may be one mechanism for the absorption of iron. Considering iron concentrations are low in human milk, the relatively high abundance of lactoferrin in breast milk may facilitate iron absorption in infants or it may protect against intestinal pathogens by sequestering iron. The existing literature contains conflicting observations on the impact of lactoferrin containing iron (holo-lactoferrin) or that is iron free (apo-lactoferrin) on iron absorption by infants. A study by Mikulic and colleagues reported in the December 2020 issue of The Journal of Nutrition addresses this issue.
A maize-based porridge was provided to 4 month old Kenyan infants in a crossover study design. The test meals contained 1.5 mg iron as 54FeSO4, 1.42 mg iron as 58FeSO4 with 1.41 g apo-lactoferrin that contained 0.08 mg iron, or 1.41 g holo-lactoferrin containing 1.5 mg iron as 57Fe. Fractional iron absorption was determined by measuring isotope incorporation in erythrocytes.
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Iron absorption was higher when the test meal contained apo-lactoferrin plus FeSO4 than with FeSO4 alone, or when the meal contained holo-lactoferrin. There were no differences in iron absorption produced by meals containing holo-lactoferrin or FeSO4 alone. The authors concluded that inclusion of apo-lactoferrin in a meal containing FeSO4 led to better iron absorption in young infants. Furthermore, they suggest that inclusion of apo-lactoferrin may protect against the adverse intestinal issues and diarrhea that occurs when diets contain unbound iron.
In a commentary on this article, Griffin discusses the important element of this study being the inclusion of a treatment arm that includes apo-lactoferrin. Although the results add to the literature, Griffin suggests the outcomes do not indicate whether lactoferrin in human milk improves iron absorption. Griffin does suggest inclusion of lactoferrin in infant diets in developing countries as a promising option to improve iron status without promoting infections.
References
Griffin IJ. The effects of different forms of lactoferrin on iron absorption. The Journal of Nutrition, Volume 150, Issue 12, December 2020, Pages 3053–3054, https://doi.org/10.1093/jn/nxaa314.
Mikulic N, Uyoga MA, Mwasi E, Stoffel NU, Zeder C, Karanja S, Zimmermann MB. Iron absorption is greater from apo-lactoferrin and is similar between holo-lactoferrin and ferrous sulfate: Stable iron isotope studies in Kenyan infants. The Journal of Nutrition, Volume 150, Issue 12, December 2020, Pages 3200–3207, https://doi.org/10.1093/jn/nxaa226.
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