Why is Sleep and Nutrition Such a Big Deal for Babies? | The Breast Milk and Infant Sleep Study The Study's Findings | Why This Study Matters? | What's the Takeaway?
Overview
If you have a newborn, you probably already researched online how to get your baby to sleep - at least once, if not a hundred times.
One of the hardest things about being a new parent is getting enough sleep (by getting your baby to sleep, of course). But here's an interesting twist: science suggests that breast milk might play a role in how well your little one sleeps.
A recent study examined the potential relationship between infant sleep duration and polyunsaturated fatty acids (PUFAs), a type of fat found in breast milk.
The findings are intriguing and may offer a completely different understanding of the relationship between sleep and nutrition during those critical early months.
Let us take a closer look at this fascinating research together!
Why is Sleep and Nutrition Such a Big Deal for Babies?
Before we delve into the study, it is essential to understand why sleep and what we feed our little ones during infancy are crucial.
Infant sleep is a complex developmental process intricately linked to body weight, cognition, and metabolism. Infants spend most of their first months of life asleep—around 70% of the day.[2]
Studies show that babies who sleep longer and more regularly in their early years may have better weight outcomes, stronger language and motor skills, and healthier long-term paths.[3]
On the other hand, not getting enough sleep or having sleep problems has been linked to developmental delays, behavioural issues, and even a higher risk of becoming obese in the future.
Concerning nutrition, experts advise that infants be fed only human milk or breast milk for the first 6 months.[4]
Human milk (HM) has a significant amount of fat, with PUFAs accounting for one-fifth of the total fat content. PUFAs are essential for crucial developmental processes such as central nervous system (CNS) maturation, retinal and brain function, and they may also influence sleep regulation.[5]
However, there is very little information on how human breast milk PUFA content affects sleep in exclusively HM-fed newborns.
The Breast Milk and Infant Sleep Study
In a fantastic new study published in The Journal of Nutrition, researchers investigated the relationship between polyunsaturated fatty acids (PUFAs) in human milk (HM) and newborn sleep patterns.[1]
This research was a secondary, cross-sectional analysis of data from a randomised controlled trial that initially focused on lactation cookies. For this study, the researchers recruited 131 mothers and their 2-month-old infants from 30 states in the United States.
Participants were eligible if their infant was healthy and born at term after a healthy pregnancy and uncomplicated birth. Sociodemographic information was collected, as well as maternal pre-pregnancy height and weight, and newborn birth weight and length.
The researchers collected data on the infants' sleep using the Parent-Reported Brief Infant Sleep Questionnaire. The main goal of the study was to determine the total time a baby spent sleeping over the course of 24 hours, including both nighttime and diurnal sleep. Secondary outcomes included sleep latency and nighttime awakenings.
Participants were requested to provide fasting milk samples for analysis.
Fatty acid methyl esters were isolated from the samples and analysed by gas chromatography-flame ionisation.
Multivariate linear regression models were utilised, with infants' total 24-hour sleep time as the primary outcome and night wakings and sleep delay as exploratory variables.
The models were adjusted for pre-pregnancy body mass index (BMI), number of feedings, infant gender, and two-month weight-for-length z-scores.
The Study's Findings
The newborns in this study slept for an average of 14.7 hours each day, with approximately 6.2 hours during the day and 8.4 hours at night.
Milk samples revealed that PUFAs accounted for roughly 21% of total milk fatty acids.
On average, omega-3s accounted for 1.8%, whereas omega-6s accounted for 19.2% of the total. Linoleic acid (LA) made up 17.7% of total HM fatty acids. Eicosapentaenoic acid, docosahexaenoic acid (mean 0.20%), arachidonic acid, and alpha-linolenic acid (ALA) accounted for 0.06%, 0.20%, 0.45%, and 1.37%, respectively.[1]
After reviewing all the analyzed data, the researchers noted some remarkable findings. Some of them are:
Total Sleep Duration
- Higher proportions of omega-3 fatty acids were associated with longer sleep.
- Higher proportions of omega-6 fatty acids were also associated with longer sleep.
- Specifically, omega-3 (ALA) and omega-6 (LA) were the strongest predictors of longer sleep duration.
Daytime vs. Nighttime Sleep
- The associations were specific to daytime (diurnal) sleep.
- More omega-3 and omega-6, especially ALA and LA, were significantly linked to more daytime sleep.
- No significant associations were found with nighttime sleep.
Sleep Latency and Nighttime Awakenings
- There were no clear links between the fatty acid composition and how quickly babies fell asleep or how often they woke up at night.
These results indicate that PUFAs, particularly ALA and LA, may impact infant sleep, albeit in an unexpected manner: by affecting daytime sleep rather than nighttime sleep.
The relative scale of change is another important detail. A 1% rise in omega-3 caused a much bigger biological change (about two standard deviations) than a 1% rise in omega-6 (about a quarter of a standard deviation).
This finding suggests that the omega-3 effects may be more significant in real-life applications, even though both were statistically significant.
Why This Study Matters?
This study is the first to demonstrate a direct link between the amount of PUFA in human milk and the quality of sleep in babies within a substantial, geographically diverse U.S. cohort.
The findings provide new insights into the relationship between nutrition and sleep during early development.
Crucially, the findings indicate that the fatty acid profile of human milk, which is influenced by maternal diet and biology, may affect infant sleep, especially diurnally.
Better sleep for babies is essential for their brain development and metabolic health, as well as for the health of the whole family. It reduces stress for parents and improves life for everyone.
For parents, the key takeaway is not to micromanage their children's diet, but to understand how sleep and nutrition are connected. These essential fats are naturally found in breast milk and may help support brain development and promote healthy sleep patterns.
Everyone benefits from a baby sleeping well: the baby grows and develops well, and the parents get a much-needed break.
What's the Takeaway?
In summary, this study demonstrated that elevated levels of omega-3 and omega-6 fatty acids in human milk - particularly alpha-linolenic acid (ALA) and linoleic acid (LA) - were associated with extended total and diurnal sleep in exclusively breastfed two-month-old infants.
These findings underscore a previously underexamined correlation between maternal milk composition and infant sleep, highlighting the necessity for ongoing research in this domain.
Learning how early nutrition affects sleep could help babies grow and develop more effectively, potentially reducing the likelihood of health problems later in life.
References:
- Palacios, A. M., Lemas, D. J., Young, B. E., Parker, E., Dickinson, S., Marshall, N., Sullivan, K. L., Wilt, H., Cardel, M. I., & Allison, D. B. (2025). Associations among human milk polyunsaturated fatty acids and infant sleep patterns: A cross-sectional study. The Journal of Nutrition. https://doi.org/10.1016/j.tjnut.2025.07.021
- KLEITMAN, N., & ENGELMANN, T. G. (1953). Sleep characteristics of infants. Journal of applied physiology, 6(5), 269–282. https://doi.org/10.1152/jappl.1953.6.5.269
- Tham, E. K., Schneider, N., & Broekman, B. F. (2017). Infant sleep and its relation with cognition and growth: a narrative review. Nature and science of sleep, 9, 135–149. https://doi.org/10.2147/NSS.S125992
- Kramer, M. S., & Kakuma, R. (2012). Optimal duration of exclusive breastfeeding. The Cochrane database of systematic reviews, 2012(8), CD003517. https://doi.org/10.1002/14651858.CD003517.pub2
- Madore, C., Leyrolle, Q., Morel, L., Rossitto, M., Greenhalgh, A. D., Delpech, J. C., Martinat, M., Bosch-Bouju, C., Bourel, J., Rani, B., Lacabanne, C., Thomazeau, A., Hopperton, K. E., Beccari, S., Sere, A., Aubert, A., De Smedt-Peyrusse, V., Lecours, C., Bisht, K., Fourgeaud, L., … Layé, S. (2020). Essential omega-3 fatty acids tune microglial phagocytosis of synaptic elements in the mouse developing brain. Nature communications, 11(1), 6133. https://doi.org/10.1038/s41467-020-19861-z
