As every parent knows, waking at night to feed a baby—whether by breast or bottle—can be incredibly hard. High on the list of tricks to eek out more precious minutes of sleep is the advice to feed the baby extra milk, to “top off” or “fill the tank” before bed. A bigger meal, or even the addition of formula or rice cereal, will make her sleep longer.
So the reasoning goes.
This turns out to be a widespread myth. Newborn babies eat frequently and sleep in short stretches because their nervous and digestive systems are developing. They take in small amounts of milk very often through the night and day; adding big bottles doesn’t mimic their bodies’ natural feeding patterns. And whether we feed them on demand or “tank them up” before bed, it doesn’t really impact their sleep. In fact, studies find that whether moms breastfeed exclusively, formula feed, or a mix of the two, they report similar sleep patterns in the first months of life. One study in which mothers wore devices to objectively measure sleep found the number of night wakings they experienced and their overall sleep time (about 7 hours of fragmented sleep) was the same regardless of breast or bottle. Another study actually found breastfeeding moms got 40 minutes more sleep per night.
Babies do tend to cluster feed in the evenings (frequent or nonstop feeding for a few hours before bed), which is thought to be a way of regulating the nervous system, taking in more calories, and preparing for sleep. But there’s no evidence that adding in an extra large bottle on top of this natural on-demand system will help. In fact, imagine yourself going to bed after drinking an extra large milkshake. Would it help you sleep better, or make you more likely to wake up?
So if it’s not food that makes baby sleep, what is it? After the first 5-6 months, the difference between babies who sleep long stretches and those who wake frequently is in the way they fall asleep, not the fullness of their tummies. Babies who go into their sleeping places awake and are able to self-soothe at bedtime are less likely to need help in the night. As the first year progresses, if we focus on good sleep habits like a regular bedtime and the unfolding ability to self-soothe, this (not over-the-top calories) will be the best predictor of good sleep for our little ones.