Does Formula Really Help Babies Sleep Better?
What a new study tells us about breastfeeding, infant sleep, and the pressure we place on mothers.
It’s advice almost every breastfeeding mother has heard at some point: “Just give the baby formula. They’ll sleep better.”
Usually, it comes from a well-meaning place. A friend or family member sees an exhausted mother, hears about another sleepless night, and offers what sounds like a simple solution.
But what if the relationship between feeding and sleep isn’t quite what we’ve been led to believe?
A new study published in the European Journal of Clinical Nutrition is giving us another reason to rethink that familiar advice.
What the research found.
Researchers analyzed data from nearly 83,000 mother-infant pairs in Japan, examining feeding patterns during the first six months of life and sleep duration at one year.
Their findings? Babies exclusively breastfed for six months had 23% lower odds of short sleep duration at age one compared with babies exclusively formula-fed.
Interestingly, the association wasn’t limited to exclusive breastfeeding. Babies who received a combination of breast milk and formula also had lower odds of short sleep duration, with stronger associations seen across groups with longer breastfeeding duration.
For context, researchers defined short sleep as fewer than 11 hours of total sleep within a 24-hour period, including naps.
This distinction matters. The study wasn’t measuring how often babies woke overnight or whether they slept through the night. And because it was observational, it cannot establish that breastfeeding directly caused longer sleep.
The findings are still worth exploring.
There’s more to breast milk than calories.
One of the most interesting aspects of this research is why breastfeeding might be associated with sleep development.
Breast milk contains melatonin, a hormone involved in regulating our circadian rhythm, or internal sleep-wake clock. Its composition also changes throughout the day, including fluctuations in tryptophan, an amino acid involved in melatonin production.
Researchers also highlighted the relationship between breastfeeding, the developing infant gut microbiome, and the gut-brain axis.
These are potential explanations, not mechanisms directly tested or confirmed by this study. But they remind us that infant feeding is complex, and sleep regulation involves much more than simply having a full stomach.
The conversation mothers actually need.
Here’s where I think this research becomes especially meaningful.
We can fully support formula feeding, combination feeding, and exclusive breastfeeding while also questioning the advice mothers receive.
Telling a breastfeeding mother that formula will solve her baby’s sleep struggles can plant a seed of unnecessary doubt.
Is my milk enough? Is breastfeeding keeping my baby awake? Am I making things harder than they need to be?
Those questions can feel particularly heavy when you’re already navigating the exhaustion of early motherhood
Formula is a valuable feeding option, and choosing it for any number of personal reasons is valid. But presenting it as a guaranteed solution for better sleep isn’t supported by this study.
Likewise, breastfeeding isn’t a promise of uninterrupted nights.
Babies wake for many reasons. Their sleep develops at different rates, and feeding method is only one small part of a much bigger picture.
A little reassurance.
If you’re breastfeeding and feeling pressure to switch solely because your baby wakes frequently, I hope this offers some perspective.
Your milk isn’t automatically the problem. And you don’t have to abandon a feeding relationship that’s working for your family based on the promise of better sleep.
If you need or want to make a change, that decision deserves support, too.
Ultimately, mothers deserve thoughtful, individualized guidance that considers both their babies’ needs and their own well-being.
Feeding decisions should be rooted in evidence and support, not exhaustion, comparison, or pressure.
The most helpful thing to offer a tired mother is reassurance, practical support, and an opportunity to rest instead of risking planting that seed of doubt by recommending other ways to feed her baby.
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Research referenced: Nakagawa et al. (2026), cohort, European Journal of Clinical Nutrition.