Cow's milk and intestinal blood loss in late infancy

Objectives: Young infants commonly show occult intestinal blood loss when fed cow's milk, but in older infants blood loss may be less common. This study examined intestinal blood loss in response to cow's milk feeding in normal 71/2-month-old and 12-month-old infants. Study design: Infants (n = 62) were fed formula for 1 month and then pasteurized cow's milk for 2 months. Stools were collected for quantitative determination of hemoglobin. Iron nutritional status was assessed. Results: Infants fed cow's milk from 71/2 months of age showed a significant increase in guaiac-positive stools and in stool hemoglobin concentration. These effects were largely limited to those infants who had been breast fed early in life. Infants fed cow's milk from 12 months of age at baseline had greater stool haemoglobin concentrations than 71/2-month-old infants, but cow's milk produced no significant increase. In neither age group did cow's milk affect iron nutritional status. Conclusion: The response to cow's milk is attenuated in infants aged 71/2 months compared with younger infants. By 12 months of age, the response has disappeared entirely. We conclude that the gastrointestinal tract of healthy infants gradually loses its responsiveness to cow's milk.