Neuro endocrinology lettersDec 29, 2005

Daily changes in breast milk tryptophan relate to newborns' melatonin levels and sleep patterns

Circadian Biology Weekly Brief ↗PubMed ↗

Updated Mar 27, 2026

Abstract

Breast-fed infants showed significantly increased sleep duration and efficiency compared to bottle-fed infants.

Tryptophan in breast milk exhibited a circadian rhythm, peaking around 03:00.
The circadian rhythm of 6-sulfatoxymelatonin in breast-fed infants peaked at 06:00.
Breast-fed infants had increased assumed sleep, actual sleep, and sleep efficiency compared to formula-fed infants.
The timing of tryptophan in breast milk may influence the sleep patterns of breast-fed infants.

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