Background. Many infants are switched between multiple formula preparations early in life because of perceived abnormalities in stooling pattern as well as gastrointestinal symptoms.

Objective. To investigate the relationship between the type of formula consumed and the stooling characteristics and gastrointestinal symptoms of young infants.

Methods. Healthy 1-month-old infants were fed one of four commercial formula preparations (Enfamil, Enfamil with Iron, ProSobee, and Nutramigen) for 12 to 14 days in a prospective double-blinded (parent/physician) fashion. Parents completed a daily diary of stool characteristics as well as severity of spitting, gas, and crying for the last 7 days of the study period. A breast-fed infant group was studied as well.

Results. Two hundred eighty five infants were enrolled and 238 completed the study. Infants receiving breast milk or Nutramigen had twice as many stools as other formula groups (P < .001). Infants receiving ProSobee had hard/firm stools more often than breast-fed or other formula-fed groups (P < .00001). Watery stools were more common in infants fed Nutramigen than other formula groups (P < .04). Green stools were more common in 12 mg/L iron preparations (Enfamil with iron, ProSobee, Nutramigen) than in those with 1 mg/L (Enfamil, breast milk) (P < .00001). Spitting, gassiness, and crying were of equal severity in all formula groups.

Conclusions. The interpretation of stool frequency, color, and consistency must take into account the infant's formula type as significant variations in normal infants occur. Parental education on the range of infant stooling characteristics as well as the common occurrence of spitting, gas, and crying may alleviate concern for formula intolerance and underlying gastrointestinal disease.

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