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correspondence

Indian Pediatr 2012;49: 592

Zinc and Copper Concentrations in Breastmilk


José G Dórea

Department of Nutrition, University of Brasília, 70919-970 Brasília, DF, Brazil,

Email: [email protected]


The concentration of essential trace elements in breast-milk is an important topic in infant nutrition. The interesting paper by Örun, et al. [1] needs to be put in context in the light of previous research on the topic. Comprehensive reviews of breastmilk zinc [2,3] and copper [4] concentrations have addressed the maternal (constitutional and environmental) factors modulating the secretion of these essential nutrients. I was surprised that the brief discussion by Örun, et al. [1] overlooked these sources. Also, compared to international data, they showed a surprisingly low mean milk-zinc concentration.

I take the opportunity to remind readers that in the case of zinc, the stage of lactation is the only variable associated with important changes in milk concentrations. In the first days postpartum, the zinc concentrations in breast-milk fall steeply, and after the first weeks, gradually decrease throughout the following 6 weeks; reaching relatively stable levels by the third month. In spite of increasing volumes of milk consumed by nursing infants, the total zinc intake falls as a function of the rate of decrease in the milk metal concentration. For postpartum days 1, 7, 15, 30, 60, 90, 120, and 180, the reported median zinc concentrations (mg/L) are 8.12, 4.56, 3.36, 2.65, 1.66, 1.35, 1.2, 0.98 and 0.93; respectively [2]. Experiments with maternal zinc supplementation aimed at enriching breast-milk have not been effective. However, maternal zinc therapy has been reported to correct abnormalities of zinc metabolism during gestation and lactation [2].

The variability of breast-milk zinc concentrations is wide; it does not depend on maternal zinc intake but it can vary within and between mothers as a function of parity, stage of lactation, and type (fore or hind milk) of feeding [2]. Therefore, to test a hypothesis that a significant association exists between this variable and anthropometry (changing in the opposite direction) requires a more appropriate study design. However, it is possible that repeated measurements of both milk zinc and anthropometry in exclusively breastfed infants, as in follow-up studies, has been useful in generating the hypothesis that the decrease in zinc concentrations can be associated with weight and linear growth [5].

References

1. Örun E, Yalçin SS, Aykut O, Orhan G, Morgil GK. Zinc and copper concentrations in breastmilk at the second month of lactation. Indian Pediatr. 2012;49:133-5.

2. Dórea JG. Is zinc a first limiting nutrient in human milk? Nutr Res. 1993;13:659-66.

3. Dórea JG. Zinc in human milk. Nutr Res. 2000;20:1645-87.

4. Dórea JG. Iron and copper in human milk. Nutrition. 2000;16:209-20.

5. Dórea JG. Zinc deficiency in nursing infants. J Am Coll Nutr. 2002;21:84-7.

 

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