There are optimal times of day to feed your baby pumped breast milk that correlate with their circadian rhythm, researchers said Friday, with potential benefits for their health and sleeping patterns.
A mother’s breast milk is unique, due to factors including nutrition, fitness, and genetics.
But levels of melatonin, for example, the hormone that regulates the body’s sleep cycle, peak at around midnight in breast milk, the researchers found. Cortisol, which manages stress, was at its highest level early in the morning.
Levels of the love hormone oxytocin, the milk protein lactoferrin, and the antibody protein immunoglobulin A were mostly stable throughout the day.
“We all have circadian rhythms in our blood, and in lactating mothers, these are often reflected in breast milk,” Dr. Melissa Woortman, from Rutgers University in New Jersey, explained in a statement.
“Hormones like melatonin and cortisol follow these rhythms and enter milk from maternal circulation,” she said.
Feeding babies expressed breast milk at a corresponding time to when it was pumped appeared to be incredibly beneficial for the infants’ health. That was particularly the case for the youngest infants, who are still developing a sleep pattern.
“We noted differences in the concentrations of bioactive components in breast milk based on time of day, reinforcing that breast milk is a dynamic food,” Woortman said. “Consideration should be given to the time it is fed to the infant when expressed breast milk is used.”
The study involved 21 participants who were recruited by Rutgers, and the University of Puerto Rico. The mothers had just given birth at New Brunswick’s Robert Wood Johnson Medical Center and were over the age of 21.
Participants gave 10-milliliter breast milk samples over the course of two days, about a month apart. The new moms provided samples of expressed breast milk at 6 a.m., noon, 6 p.m., and midnight.
Samples were also collected from 17 additional participants at the same times, but only for one day. A total of 236 samples were analyzed.
Labeling stored milk with the time of day it has been pumped could be a way to ensure babies receive important signals thought to influence their sleep-wake cycles. That may especially be beneficial for busy mothers who don’t have the opportunity to directly breastfeed multiple times during the day and night.
“Labeling expressed milk as ‘morning,’ ‘afternoon,’ or ‘evening’ and feeding it correspondingly could help align expressing and feeding times and preserve the natural hormonal and microbial composition of the milk, as well as circadian signals,” Professor Maria Gloria Dominguez-Bello, a researcher at Rutgers University, pointed out.
