Introduction: Melatonin is an antioxidant, a circadian pacemaker, and an immune system stimulator. Studies have demonstrated beneficial effects of melatonin on various conditions in neonates. Melatonin is secreted in breast milk in circadian rhythm, but its half-life and stability in this medium and in real-life conditions of freezing and defrosting is unknown. The objective of this feasibility study was to evaluate stability of melatonin in breast milk after freezing and defrosting. Methods and Results: Breast milk samples of nocturnal milk and daytime milk were collected from 13 healthy breastfeeding mothers and were immediately frozen. Samples were defrosted in room temperature and were sampled for melatonin immediately and every hour for 4 hours and at 24 hours after defrosting. Melatonin levels were measured with Melatonin direct Saliva ELISA kit (IBL International).There was no statistically significant difference between levels at the different time points (p = 0.696). Melatonin levels in daytime milk were significantly lower than night-time levels (p = 0.028). Conclusion: Melatonin is stable in human milk for at least 4 hours after defrosting and even up to 24 hours. Further research of the therapeutic potential of night breast milk high in melatonin is needed.
Keywords: ELISA; breast milk; lactation; melatonin; neonate.