A landmark study of 99 seven-year-olds born very preterm shows that more protein in the first two weeks of life leads to more mature brain development—but the story is surprisingly complex.
Every year, about 10% of babies worldwide are born preterm. For those born very preterm—before 30 weeks or weighing less than 1500 grams (about 3.3 pounds)—the first days of life are a race. Their tiny bodies are not ready for the outside world. Their brains are still developing at a furious pace, but now without the protected environment of the womb.
Doctors face a critical question: What is the ideal nutrition to feed these vulnerable infants? Too little, and the brain may not grow properly. Too much, and there may be unforeseen consequences.
A landmark new study published in JAMA Network Open followed 99 children born very preterm from birth to age 7. The researchers compared two groups: those born just before a hospital changed its nutrition protocol (lower protein) and those born just after (higher protein). The results are both encouraging and nuanced.
The Experiment That Nature Provided
In 2007, the neonatal intensive care unit (NICU) at National Women’s Hospital in Auckland, New Zealand, updated its nutrition guidelines. The goal was simple: increase early protein intake and decrease fluid intake.
This created a natural experiment. Babies born between July 2005 and December 2006 received the “old protocol” (lower protein). Babies born between January 2007 and October 2008 received the “new protocol” (higher protein).
At age 7, the children underwent advanced brain scans (MRI) to measure:
- Brain volumes (how much space the brain occupies)
- Cortical thickness (the outer layer of the brain, responsible for complex thinking)
- White matter microstructure (the “wiring” that connects different brain regions)
The results tell a fascinating story about how early nutrition programs the brain for years to come.
The Numbers: What Did the Two Groups Receive?
The difference in protein intake was clear and significant:
| Nutrition Period | Old Protocol (Lower Protein) | New Protocol (Higher Protein) | Difference |
|---|---|---|---|
| Days 1-7 | 17 g/kg | 21 g/kg | +4 g/kg (24% more) |
| Days 1-14 | 41 g/kg | 45 g/kg | +4 g/kg (10% more) |
Both groups had similar intakes of fat, energy, and breast milk.
In plain English: the new protocol group received about one extra gram of protein per kilogram of body weight per day in the first week. For a 1 kg baby, that is like adding an extra egg white worth of protein daily.
Finding #1: Thinner Cortex, More Mature Brain
The most striking finding involves cortical thickness. The new protocol group (higher protein) had significantly thinner lateral occipital and lateral parietal cortices than the old protocol group.
At first glance, “thinner” sounds bad. But in brain development, thinning is a sign of maturation.
Think of the brain like a garden. In early development, the brain overproduces connections (like overgrown weeds). As a child grows, the brain prunes away unnecessary connections, leaving only the strongest, most efficient pathways. This pruning appears on MRI scans as cortical thinning.
Key Cortical Thinning Differences (New Protocol vs. Old Protocol)
| Brain Region | Thickness Difference | Statistical Significance | What It Means |
|---|---|---|---|
| Lateral Occipital (Left) | -0.16 mm | p < 0.001 | Highly significant thinning |
| Lateral Occipital (Right) | -0.17 mm | p < 0.001 | Highly significant thinning |
| Lateral Parietal (Right) | -0.25 mm | p < 0.001 | Significant thinning |
| Lateral Parietal (Left) | -0.21 mm | p = 0.01 | Thinning (trend) |
The lateral occipital cortex handles visual processing. The lateral parietal cortex integrates sensory information.
The researchers interpret this thinning as advanced brain maturation. The higher-protein group’s brains were pruning more efficiently, reaching a more adult-like state earlier.
This interpretation is supported by earlier findings from the same cohort: higher protein intake was associated with stronger functional connectivity between brain networks (published separately) and better motion perception (a measure of visual processing efficiency).
Finding #2: More Extracerebral Space, Same Brain Size
The new protocol group had a smaller brain volume as a percentage of intracranial volume (80% vs. 86%). But here is the surprise: absolute brain volumes were the same between groups.
This means the new protocol group had larger skulls (intracranial volume) but the same-sized brains. The mechanism for this is unclear, but it is consistent with previous research showing that breastfeeding is associated with larger intracranial volume without larger brain volume.
In practical terms: the higher-protein babies grew bigger heads, but their brains filled proportionally less of that space. This is not necessarily good or bad—it is simply a difference that requires further study.
Finding #3: Better White Matter “Wiring”
When the researchers combined data from both groups (looking at individual protein intake rather than group assignment), a clear pattern emerged:
Children with greater protein, fat, energy, and breast milk intake had more mature white matter microstructure.
White matter is the brain’s “internet cable.” It consists of axons (the wires) covered in myelin (the insulation). More mature white matter has:
- Higher fractional anisotropy (FA): More directional, organized wiring
- Lower mean diffusivity (MD): Less random water movement, indicating tighter insulation
This pattern was observed across almost every major white matter tract studied—including those responsible for language, attention, and sensory processing.
White Matter Maturation (All Children Combined)
| Nutrient | Effect on White Matter | Interpretation |
|---|---|---|
| Higher Protein | More mature microstructure (higher FA, lower MD) | Better brain “wiring” |
| Higher Fat | More mature microstructure | Better brain “wiring” |
| Higher Energy | More mature microstructure | Better brain “wiring” |
| More Breast Milk | More mature microstructure | Better brain “wiring” |
These associations were consistent across multiple brain tracts.
The Complicated Picture: Not All Good News
The researchers are careful to note that higher protein intake is not an unalloyed good. In previous reports from this same cohort:
- Higher protein intake was associated with an increased rate of cerebral palsy (though the absolute numbers were small: 0% in old protocol vs. 11% in new protocol, a difference that approached but did not reach statistical significance).
- Higher protein intake was associated with reduced binocular vision (stereopsis).
A separate randomized trial (the ProVIDe trial) found that additional amino acid supplementation in extremely low birth weight infants was associated with a higher likelihood of moderate or severe disability at 2 years of age.
The message is clear: nutrition is a double-edged sword. More protein promotes brain maturation in some domains (visual processing, functional connectivity, white matter organization) but may increase risk in others (motor development, binocular vision).
Why This Matters for Parents and Doctors
For parents of preterm infants, this research offers both reassurance and guidance.
First, the reassurance: Children born very preterm can and do develop beautifully. The children in this study—now 7 years old—showed no differences in weight, height, head circumference, or overall neurodevelopmental impairment between the two nutrition groups. They are, by all standard measures, healthy children.
Second, the guidance: Early nutrition matters. The first two weeks of life are a critical window for brain development. The differences observed at age 7—thinner cortex, better white matter organization—trace back to those first 14 days of life.
Hospitals should continue to refine their nutrition protocols, balancing protein intake against potential risks. The optimal amount may differ for each infant based on gestational age, birth weight, and other medical factors.
What This Study Could Not Tell Us
No study is perfect. The authors honestly note several limitations:
- Not randomized: The two groups were born at different times. Other changes in hospital care (besides nutrition) could have influenced the results.
- Attrition: Not all eligible children completed the MRI scans. Those who did may not represent the whole population.
- Sample size: With 99 children, the study is large for this type of research but still limited in its ability to detect small effects.
- Single site: All children came from one hospital in New Zealand. Results may differ elsewhere.
The Bigger Picture: Personalizing Preterm Nutrition
The ultimate goal is not to find a single “magic formula” for all preterm infants. It is to understand how genetics, environment, and nutrition interact to shape each unique brain.
Some infants may thrive on higher protein. Others may experience adverse effects. Future research will likely focus on identifying biomarkers that predict which infants will benefit most from aggressive nutrition and which should be treated more conservatively.
The Bottom Line
This study of 99 children born very preterm provides strong evidence that neonatal protein intake influences brain development for years to come.
Children who received more protein in the first two weeks of life had:
- Thinner, more mature visual and parietal cortices
- Better organized white matter “wiring”
- No differences in overall brain size or neurodevelopmental outcomes
But higher protein also carried risks in other studies (cerebral palsy, binocular vision problems), reminding us that there is no free lunch in medicine.
For parents sitting in a NICU right now, watching their tiny baby fight for life, the message is hopeful: the food you give them today will shape their brain for years. And with careful, personalized care, those brains can flourish.
Citation: Poppe, T., et al. (2025). Neonatal Nutrition and Brain Structure at 7 Years in Children Born Very Preterm. JAMA Network Open, 8(1), e2456080.
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