The biggest hazards for babies are prematurity and necrotizing enterocolitis (NEC). Babies that leave the uterus before they induce labor tend to be born with immature guts. Immaturity of the gut leads to a spectrum of complications that is further aggravated by early weaning and use of infant formula.
Several studies show that allergy risks, for example, are reduced by introducing solids while breastfeeding continues for the first year. Progress in the study of these risks to infants has been slowed by lack of adequate animal model systems to study the hazards of infant formula to premature infants.
Breast Milk Protects and Supports Maturation of Infant Intestines
Birth of infants before they are mature enough to stimulate labor results in immature, low birth weight infants that require additional support. Their lungs and guts (stomach and small intestines) frequently require special care. Breastfeeding enhances maturation and protection of immature organs, because breast milk contains hormones (prostaglandins, cytokines, growth factors), antibodies, anti-microbial components (lactoferrin, fatty acids, oligosaccharides) and maternal lymphocytes. Mother’s milk also contains prebiotic oligosaccharides that prevent the establishment of inflammatory adult bacteria and stimulate probiotic, anti-inflammatory gut flora. Formula attempts to approximate mother's milk, but the deficiencies delay gut maturation, promote inflammation and increase the risk of numerous infectious and autoimmune diseases.
Maturation of Infant Guts is Difficult to Study
Maturation of infant stomachs and intestines is complex. Unfortunately few mothers can be expected make even a minimal sacrifice of their baby’s health and comfort for a scientific study. Most of the procedures required for study of intestinal maturation are too intrusive to be performed on premature newborns.
Leaky Immature Gut and Inflammation are Major Threats
Formula feeding to premature infants causes a decrease in weight gain, production of inflammatory cytokines and slow emptying of the stomach. The use of formula also increases the risk of intestinal infections and allergies. An animal model was sought to duplicate these outcomes, so that potential improvements to formula could be developed to more closely approximate the use of mother’s milk when it cannot be used.
Rat Model Duplicates Formula Risks to Infants
A rat model was developed by Tooley, et al. at Women's and Children's Health Research Institute, North Adelaide, South Australia to duplicate the symptoms of formula-based inflammation. Four-day old rats were fed by intra-gastric cannula for 20 minutes per hour. These rats were fed with a formula equivalent to infant formula, but adapted for the nutritional requirements of rats.
Analysis of the breath, blood and intestines showed that these rats duplicate all of the symptoms of delayed intestinal maturation, inflammation and altered stomach emptying observed in formula-fed premature infants. The researchers were also able to observe a decrease in brain development and an increase in intestinal weight due to heightened recruitment of inflammatory lymphocytes and macrophages.
Many of the formula-induced changes of the gut mimicked premature weaning. Thus, the rat model appears to be suitable for testing supplements to reduce the health risks of feeding formula to infants.
Reference:
Tooley KL, Howarth GS, Butler RN, Lymn KA, Penttila IA. 2008. "The Effects of Formula Feeding on Physiological and Immunological Parameters in the Gut of Neonatal Rats." Dig Dis Sci. Oct 31. [Epub ahead of print]
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