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Child Health Research Institute
Women's Youth and Children's Health Service
Department of Pediatrics
University of Adelaide
72 King William Road
North Adelaide SA 5006
Australia
E-mail: makridesm{at}mail.wch.sa.gov.au
Dear Sir:
The purpose of our systematic review was to evaluate the effect of supplementing infant formula with long-chain polyunsaturated fatty acids (LCPUFAs) on the growth of term infants (1). Growth was the primary focus because it is often used by health workers and public health authorities to assess the nutritional health and well-being in preverbal children. Our review included data from 14 randomized controlled trials of formula feeding with 1846 infants and showed no significant effect of LCPUFA supplementation on infant weight, length, or head circumference at any assessment age, regardless of the type [only n–3 LCPUFA or n–3 LCPUFA plus arachidonic acid (AA)] or the source (phospholipid or triacylglycerol) of supplementation (1). The original impetus to add AA to infant formulas was based on the results of early small-scale trials that used formulas containing only n–3 LCPUFAs, which suggested that preterm infants fed formulas supplemented with n–3 LCPUFAs alone had lower plasma AA concentrations and weighed less and were shorter than preterm infants fed standard unsupplemented formulas (2–4). Although term infants fed n–3 LCPUFAs alone also had a lower AA status, our data clearly show that their growth is not compromised (1).
Kuratko et al from Martek Biosciences, who market AA and docosahexaenoic acid (DHA) supplements for infant formula, do not dispute our findings, but they are concerned that readers may interpret these findings to indicate that AA supplementation of infant formulas is unnecessary and suggest that AA may be required for neurologic and immune development. This issue was not an objective of our review and, therefore, was not extensively discussed. However, few trials have been specifically designed to assess the health effects of AA supplementation. Only 3 trials involving term infants compared DHA plus AA supplementation with n–3 LCPUFA supplementation alone and a control (5–7). Two of the 3 trials involving >200 infants found no differences in either visual or neurologic outcomes through 2 y of age (5, 7). Only one study involving 68 infants reported a benefit of DHA plus AA supplementation at a single assessment age (6). We are aware of no published trials that assessed the addition of only AA to infant formula. Definitive statements regarding the specific health effects of AA can only be made after a sufficient body of evidence is aggregated from appropriately designed randomized controlled trials with sufficient power to detect effects if they are there.
The issue of environmental contaminants in LCPUFA supplements for infant formulas and their influence on growth was not specifically addressed in our review. No published data regarding concentrations of lipophilic pollutants or heavy metals in infant formulas are available. However, our discussions with the infant formula manufacturers that provided data for our systematic review indicated that, although highly purified oils are used in the manufacture of infant products, levels of pesticides and heavy metals in infant formulas are at a minimum. It is therefore unlikely that infant formulas are contaminated with concentrations of pollutants, such as polychlorinated biphenyls, that are likely to cause adverse consequences.
In conclusion, the data from any systematic review and meta-analysis is only as robust as the data from the trials reviewed. We were fortunate to have completed a collaborative review with data from high-quality trials conducted both by industry and by academia. We found no evidence that LCPUFA supplementation of infant formula influences the growth of term infants in either a positive or a negative way (1). The challenge now is to assemble new and existing data in robust systematic reviews of other health effects of LCPUFA supplementation in formula-fed infants.
ACKNOWLEDGMENTS
The authors had no conflict of interest.
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