Melatonin has been shown to have a significant decrease in inflammation, oxidative stress and cell death, especially when given to pre-term infants. Furthermore, the sleep hormone has been found to improve the clinical outcomes of pre-term infants with neonatal sepsis within 24-72 hours of being administered.

Donor breast milk banks are used when mothers cannot supply their own breast milk and can be especially helpful for sick or premature babies.

In Australia, donor banks use high-temperature pasteurisation to ensure bacteria and viruses are destroyed in the breast milk before consumption. However, the consequence of this on melatonin has been put under the microscope by experts investigating the impacts of pasteurisation on melatonin in breast milk.

Research led by Dr Lauren Booker, at La Trobe’s School of Psychology and Public Health, revealed the high-temperature pasteurisation significantly reduced melatonin levels in breast milk.

“Melatonin is considered a potential new tool for neuroprotection in pre-term newborns, however our project showed melatonin in breast milk declined significantly, on average by 23.6 per cent, following pasteurisation,” Dr Booker said.

“Even though breast milk melatonin decreased significantly after pasteurisation, it was still detectable at levels that could impact an infant’s circadian timing if consumed at the wrong time of day.”

Breast milk contains hormones that exhibit a 24-hour circadian rhythm, with melatonin detected at night but barely detectable during the day, providing sleep or wake signals to the infant. Past research has found altered hormonal timings could affect the establishment of a healthy sleep cycle in infants and potentially cause long-term health impacts.

“There are no current policies at Australian donor breast milk banks to consider the timing of breast milk expression from donor mothers and the presence of circadian timed hormones, such as melatonin,” Dr Booker said.

Dr Booker suggested donated breast milk should be time-stamped to reflect when it was expressed, and the pasteurisation could be undertaken in batches based on the time of day the milk was expressed.

“As growing evidence of research reveals potential consequences in giving infants mixed or mistimed hormones in breast milk, it is important to consider the amount of melatonin in donor breast milk and its effect on pasteurisation,” Dr Booker said.