Are breast-fed infants more resilient? Feeding method and cortisol in infants.

The effect of feeding method on stress hormone levels in infants is unknown. We studied infants from birth to 1 year and found salivary cortisol 40% higher in breast-fed infants compared with formula-fed infants. The higher cortisol levels among breast-fed children may be involved in the analgesic effect of breastfeeding.