Preliminary Exploration into the Impact of Mistimed Expressed Breast Milk Feeding on Infant Sleep Outcomes, Compared to Other Feeding Patterns

Maternal Circadian Disruption from Shift Work and the Impact on the Concentration of Melatonin in Breast Milk

Background and Objective: Melatonin in breast milk exhibits a 24-hour circadian rhythm, present in nighttime breast milk but nearly undetectable in daytime breast milk. Shift work can disrupt the circadian timing of individuals, evident in changes in melatonin in saliva and urine samples. However, it is unknown whether these changes are also reflected in breast milk from a shift working mother. The aim of this study was to investigate whether maternal circadian rhythm disturbance from shift work impacts the melatonin concentration in breast milk. Materials and Methods: Breast milk and saliva samples were collected from 11 shift working mothers at four timepoints across five consecutive days. This included during their day shift or nonworkdays to act as a control, night shift, subsequent night shifts and postnight shift. Where possible, pre- and postfeed collections were also undertaken. Samples were grouped into four-time intervals: 12-6:30 am, 7-11:30 am, 12-6:30 pm, 7-11:30 pm, and melatonin levels (picogram per milliliter) in the breast milk and saliva samples were analyzed. Results: There was a significant decrease in breast milk melatonin (p = 0.026) at the 12-6:30 am time interval on subsequent night shifts, compared with control days. However, there was no overall time and shift type interaction effect (p = 0.70). In addition, no observed difference in melatonin levels was found in saliva samples, or when comparing pre- and postfeed breast milk. Breast milk melatonin however was found to be significantly higher compared with saliva (p > 0.001), at all but one time interval. Conclusion: The findings suggest that there is a potential effect of maternal circadian rhythm disruption from shift work on breast milk melatonin levels. This is an important step in exploring the role of maternal circadian timing and the effect on breast milk composition. Expansion of this research and exploration of other circadian rhythm misalignment sleep disorders on breast milk is highly recommended.

Rapid Versus Slow Cooling Pasteurization of Donor Breast Milk: Does the Cooling Rate Effect Melatonin Reduction?

Background and Objective: There is a question as to whether melatonin levels in breast milk are impacted by the cooling rate postpasteurization. Past research that has used in the Australian donor bank's breast milk Holder Pasteurization technique has reported varying findings regarding melatonin levels postpasteurization. Where breast milk was cooled slowly, a significant reduction in breast milk melatonin levels was observed. Conversely, where a rapid cooling method was used, there was no significant reduction in melatonin levels. The aim of this study was to investigate whether the cooling process between the different pasteurization techniques impact on melatonin levels in breast milk postpasteurization. Materials and Methods: Twenty-seven nighttime breast milk samples were collected, with each sample divided into three; one remained unpasteurized, one was pasteurized and rapidly cooled to 4°C, and the other was pasteurized and cooled slowly to 4°C. Results: Melatonin levels were significantly reduced in both the rapidly cooled and slow cooled breast milk samples when compared to their unpasteurized counterpart (p < 0.001). There was no significant difference in melatonin levels between the two cooling methods (p = 0.91). Conclusion: This study showed that both the rapid and cooling pasteurization processes had a similar reduction in melatonin levels in breast milk. However, even after pasteurization melatonin was still present. Therefore, it is recommended that donor banks still take into consideration circadian timing hormones such as melatonin and the time of day breast milk is expressed.

Effects of the neonatal intensive care environment on circadian health and development of preterm infants

The circadian system in mammals ensures adaptation to the light-dark cycle on Earth and imposes 24-h rhythmicity on metabolic, physiological and behavioral processes. The central circadian pacemaker is located in the brain and is entrained by environmental signals called Zeitgebers. From here, neural, humoral and systemic signals drive rhythms in peripheral clocks in nearly every mammalian tissue. During pregnancy, disruption of the complex interplay between the mother's rhythmic signals and the fetal developing circadian system can lead to long-term health consequences in the offspring. When an infant is born very preterm, it loses the temporal signals received from the mother prematurely and becomes totally dependent on 24/7 care in the Neonatal Intensive Care Unit (NICU), where day/night rhythmicity is usually blurred. In this literature review, we provide an overview of the fetal and neonatal development of the circadian system, and short-term consequences of disruption of this process as occurs in the NICU environment. Moreover, we provide a theoretical and molecular framework of how this disruption could lead to later-life disease. Finally, we discuss studies that aim to improve health outcomes after preterm birth by studying the effects of enhancing rhythmicity in light and noise exposure.

High-Temperature Pasteurization Used at Donor Breast Milk Banks Reduces Melatonin Levels in Breast Milk

Background and Objective: Donor human milk banks are used when breast milk directly from mothers is unavailable or insufficient. Breast milk contains melatonin, which exhibits a 24-hour pattern. Melatonin promotes sleep onset and is barely detected in daytime milk but rises in the evening and peaks early in the morning. Melatonin supports the development of an infant's own circadian rhythm and is important for neurodevelopment. Currently, donor banks pasteurize breast milk using a Holder Pasteurization (HoP) technique where breast milk is treated at a high temperature (+62°) for 30 minutes before cooling to eliminate any pathogens before it is given to infants. It is not known how the pasteurization process affects the melatonin levels in breast milk. The aim of this study was to investigate whether the pasteurization process reduces melatonin levels in breast milk. Materials and Methods: Ten night-time breast milk samples were collected and each divided into two groups; one group remained unpasteurized and the other group was pasteurized using the HoP technique. Results: Melatonin levels between the unpasteurized and pasteurized groups were compared. Results showed that there was a significant reduction after pasteurization (mean ± standard deviation = 51.92 pg/mL ± 19.54 versus 39.66 pg/mL ± 13.05, p = 0.01). Conclusions: It is important to understand that pasteurization can reduce melatonin levels in breast milk because this hormone is considered important to support the neurodevelopment of infants, especially those born preterm. Further focus on the effect of pasteurization techniques on melatonin in donor breast milk is warranted.