Researchers in Spain analyzed the content of breast milk samples. They found a “circadian rhythm” for some nucleotides in the milk. The levels of some nucleotides rose at night; others rose during the day.
"This made us realize that milk induces sleep in babies," lead author Cristina Sánchez told The Telegraph.
She said the finding is important for mothers who pump and store milk for later. Milk pumped during the day shouldn’t be given to a baby at night.
"It is a mistake for the mother to express the milk at a certain time and then store it and feed it to the baby at a different time," she said.
Another study suggests that a mother’s laughter may be good medicine for a sleepless baby. It found that mothers who watched a funny movie had increased levels of melatonin in their breast milk. Melatonin is a hormone that helps regulate your sleep-wake cycle.
Other studies show that breastfeeding may provide additional sleep benefits.
One study involved 196 habitually snoring children. Results show that the severity of sleep-disordered breathing was much lower in children who had been fed breast milk for at least two months.
In 2006 a study suggested that breastfeeding may protect against bedwetting; infants who were breastfed for longer than three months were less likely to suffer from bedwetting during childhood.
Another study found that breastfeeding also may help parents sleep. Parents of breastfeeding infants slept about 40 to 45 minutes longer than parents of infants who were given formula. They also reported less sleep disturbance.
The U.S. Surgeon General recommends that babies be fed only breast milk for the first six months of life.