The Science of the Food-Sleep Connection

156732403When my partner and I work with new parents, we’re often asked if feeding a baby more will help her sleep longer at night. You’ve heard the idea before — that “filling the tank” begets better sleep, and that a big bottle of breast milk, or even formula or rice cereal, will conk your baby out for long stretches.

It sounds logical — big, satisfying meal: better sleep. But as tempting as it is to think this way, it’s an idea that, as our babies grow, doesn’t necessarily hold true. In fact, eventually it becomes a mentality that works against their sleep. Learning to tell the difference is one of the keys to helping babies and children get the healthiest sleep possible.

The research on feeding and sleep makes it clear there’s a loose connection between the two. Studies don’t support the idea of feeding a baby rice cereal or formula before bed to fill up her belly. In fact, research shows feeding methods don’t make much of a difference in sleep quality overall. A study in the journal Pediatrics monitored sleep patterns of women and babies between two and 12 weeks postpartum and showed that the number of night wakings, sleep quality, and total sleep time did not differ between the exclusively breastfeeding or formula feeding mom-baby pairs. Having large bottles did not lead babies to sleep better through the night. Another study found that exclusively breastfeeding moms actually slept 40 minutes longer than mixed or formula-feeding moms.

Thinking that a baby needs a big bottle to sleep well can have its downsides — like the risk of causing a breastfeeding mom’s decrease in milk supply. This tends to happen in the evenings, when young babies naturally become fussier and “cluster feed.” We meet moms all the time who worry this means they don’t have enough milk. They give the baby a bottle in the evening to fill them up (without pumping at the same time), only to realize a few weeks later that now they actually do have a drop in breast milk. Evening fussiness and frequent breastfeeding is in fact very natural for babies — a way of helping them regulate their nervous systems and feed just enough for their bodies — which is why the American Academy of Pediatrics says, “The infant who is fussy at night or constantly feeding for several hours is not an indication of the need for supplementing.”

Not surprisingly, feeding and sleeping behaviors change as babies mature — one of the best ways to encourage sleep is to watch for signs of that change rather than repeating patterns automatically. In the first months of life, babies do wake up a lot, and responding to them with feeding is important. They have small tummies and small energy reserves, and frequent nursing is key to the breast milk supply. As bodies grow, though, waking up at night doesn’t always equal hunger. In fact, babies wake for all kinds of reason — noise, temperature, habit, the desire for soothing, and more. They have sleep cycles that repeat every 60 minutes and plenty of opportunities for rustling awake from a light sleep at least that often. The circadian system — a biological timekeeper that eventually tells our babies to sleep when it’s night and be awake during the day — matures over the first six months of life. Before it does, babies can simply wake up because their nervous systems tell them to. The impulse to immediately feed them is strong (it was the ticket in the early months), but not always needed. We nudge moms and dads to expand their “repertoire” of ways to soothe, figuring out if a baby is truly signaling hunger rather than assuming so. The more parents create that small space, the more chances babies have to naturally drop their feedings over time.

In fact, as babies grow, especially towards the end of the first year, they actually become more like us when it comes to eating and sleeping. If you eat a big, heavy meal right before bed, it activates and even upsets your digestive system, and you might sleep more fitfully and wake up to pee. As babies mature, along with their ability to sleep longer stretches, the same is true for them: more stimulation for their bodies and plenty of wet diapers.

It’s a shift in thinking, from the food-equals-sleep mentality of the newborn months, to the curiosity that allows babies to stretch out sleep as the months go on. The more we’re aware of that shift, the better the family will sleep.


Heather Turgeon, MFT is the co-author of the new book The Happy Sleeper: The Science-Backed Guide to Helping Your Baby Get a Good Night’s Sleep (Penguin Random House). She writes the long-running “Science of Kids” column for Babble.

Image: Thinkstock.

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