Overview

• Melatonin in breast milk peaks around midnight, while cortisol is highest in the early morning, indicating circadian variation.
• The Rutgers-led study analyzed 236 expressed milk samples collected at 6 a.m., noon, 6 p.m., and midnight on one or two days.
• Oxytocin, immunoglobulin A (IgA), and lactoferrin were largely stable across the day, though cortisol, IgA, and lactoferrin were higher for infants under one month.
• The authors recommend labeling pumped milk by time of day and feeding it at corresponding times to preserve circadian signals.
• Researchers note limits including sample size and demographics and call for larger cohorts and trials that track infants’ physiological and behavioral responses.