1. Morin, Karen H. DSN, RN

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I heard recently from Michelle Searly, RN, BScN, BHSc, a Public Health Nurse in Ontario, who asked about the use of water that has undergone a softening process. She wondered whether using softened water to mix powdered formula might place an infant at risk of some adverse health outcomes. I have wondered about bottled water, and thus these two topics are the focus of this column.

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What Do We Know About Water Softeners and Their Impact on Infants?

Empirical evidence addressing this question is difficult to find. Water hardness is determined by the concentration of calcium and magnesium. Higher concentrations of these two minerals result in "harder" water and can make soaps and detergents less effective, leading to excessive build-up in plumping pipes. Consequently, some individuals choose to use water-softening systems, which replace the calcium and magnesium ions with sodium or potassium ions. But if your water is "softened" and you use it to mix formula, are those increased sodium ions a good thing? Although an extensive search for this column found that there are no clear guidelines for sodium intake in infants (, it would not be unusual if parents asked you about neonatal hypertension in this circumstance. According to Pomeranz, Dolfin, Korzets, Eliakim, and Wolach (2002), the typical sodium concentration in drinking water in industrialized countries is less than 20 mg/L. Pomeranz et al. (2002) found that neonates in Israel who were fed a formula diluted with high-sodium tap water (concentrations of 196 mg/L, which are typical for the coastal plain area of Israel) had higher systolic and diastolic blood pressures at 6 and 8 weeks than those who were fed a formula diluted with low-sodium mineral water or those who were breastfed. This study, at least, did find that infants fed with water having higher sodium content than that found in North American tap water had higher blood pressures. Based on this study, it seems that if parents wish to install a water-softening system, nurses should advise them to consult the manufacturer about the amount of sodium produced by their system. Parents may also wish to install a good water filtration system to remove additional sodium ions. Lastly, they may wish to use the softening system installed on the hot water lines only, thereby bypassing the cold water lines. Doing so should obviate any concerns about excessive sodium in diluted powdered formula.


What About Bottled Water?

Similar concerns are present when considering bottled water. Azoulay, Garzon, and Eisenberg (2001) compared the mineral content in North American tap water, North American bottled waters, and European bottled waters. Sodium content in North American tap water measured 35 (+41) mg/L, that in North American bottled mineral water measured 371 (+335) mg/L, and in European highly mineralized bottled water it measured 1,151 (+152) mg/L. In this study, North American tap water had the lowest sodium content. Interestingly, findings indicated that mineral content in tap water may vary with geographic location and, in some instances, with city location. This study did not examine the effect of using the water in infant feeding but rather solely the sodium content.


Two other concerns warrant discussion in relation to bottled water: the issue of sterility and the absence of fluoride. Parents should be instructed that bottled water should not be considered sterile unless clearly indicated on the label. If bottled water is used to prepare formula for infants younger than 4 months, parents should be instructed to boil it (Law, 2004).


Although fluoride is present in natural sources of water, most bottled waters do not contain fluoride. Because fluoride is essential for an infant's developing teeth, using bottled water that is not fluoridated can have serious health outcomes. Bottled water, therefore, should not be used when preparing infant formula unless the water contains fluoride.




Azoulay, A., Garzon, P., & Eisenberg, M. J. (2001). Comparison of the mineral content of tap water and bottled waters. Journal of General Internal Medicine, 16, 168-175. [Context Link] Retrieved June 9, 2006, from[Context Link]


Law, M. (2004). Bottle feeding with lots of cuddling. Parents Canada. Retrieved 9th February 2006, from[Context Link]


Pomeranz, A., Dolfin, T., Korzets, A., Eliakim, A., & Wolach, B. (2002). Increased sodium concentrations in drinking water increase blood pressure in neonates. Journal of Hypertension, 20, 203-207. [Context Link]