Digesting formula can be toxic to cells that line the gastrointestinal tract.
PROBLEM: An often fatal intestinal disease, necrotizing enterocolitis (NEC) disproportionally targets premature infants -- particularly those that are given formula instead of being breastfed. While the correlation between formula and NEC has long been known, the causation remains elusive.
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METHODOLOGY: No infants were harmed in the testing of this theory. Instead, UC San Diego bioengineers mixed intestinal fluids in petri dishes with fresh human breast milk and nine different infant formulas. After each type of milk had been "digested," they tested for levels of free fatty acids, which have been shown in adult stomachs to damage cell membranes. To see whether this was applicable to NEC, they also tested whether the free fatty acids were capable of killing three types of cells implicated in the disease.
RESULTS: Cells that line the intestine and blood vessels, along with white blood cells that control inflammation caused by trauma, were virtually eliminated during the process of digesting formula. At the extreme end of this, 99 percent of cells would die in under five minutes. The digestion of breast milk was responsible for only minimal cell death.
CONCLUSION: Breast milk is able to significantly reduce cell death, while formula may lead to the development of NEC in infants.
IMPLICATION: Premature infants are often fed formula for their duration of time in the NICU. These findings underscore the importance of putting in the extra effort necessary for getting breast milk to them instead.
Full-term and otherwise healthy infants, too, are encouraged to be fed breast milk, especially if they are at risk for disorders like autism, which is associated with gastrointestinal problems.
The full study, "Digested formula but not digested fresh human milk causes death of intestinal cells in vitro: implications for necrotizing enterocolitis," is published in the journal Pediatric Research.