The Fat in the Drip: How a Fish-Oil Nutrition Blend Protects Premature Babies' Livers

What families should know about a large review of SMOFlipid, a modern intravenous feeding fat used in newborn intensive care

When a baby is born very early or too sick to feed by mouth, nutrition is given straight into a vein—a method called parenteral nutrition. A large review that combined 20 separate clinical trials, involving 1,904 newborns, found that one modern fat blend used in that intravenous feeding, called SMOFlipid, lowered the risk of a common liver complication by about a third compared with older fat blends [1]. The review also found a small benefit for the heart in the tiniest babies, but no clear effect on the lungs, eyes, brain, or survival. This article explains what that means, in plain language, for families whose baby is receiving intravenous nutrition.

Why This Question Matters

Premature and surgically ill newborns often cannot digest milk for days or weeks. Their intestines may be too immature, or they may be recovering from an operation. Until they can feed, everything their growing body needs—sugar, protein, vitamins, minerals, and fat—must be delivered through a thin tube into a vein [2]. Fat is a crucial part of that mixture. It is the most concentrated source of energy, and it supplies the special building blocks that a baby's brain, eyes, and cell membranes are made from. Without it, a fragile newborn simply cannot grow.

But the fat in the drip has a hidden cost. For decades, the standard product was made purely from soybean oil. It works, but over weeks of use it can stress and inflame the liver, leading to a problem doctors call cholestasis—a backing-up of bile that shows as jaundice, a yellowing beyond the ordinary newborn kind, and rising liver markers on blood tests [1]. In babies who need many weeks of intravenous feeding, this liver strain became one of the quiet, worrying complications of otherwise life-saving nutrition.

How Families and Doctors Used to Face This

For a long time there was little to do about it except watch and wait. Doctors monitored the baby's liver with regular blood tests and tried to start milk feeds as soon as the intestine could tolerate them, because the fastest way to rest the liver is to stop the intravenous feeding altogether [3]. When cholestasis became severe, the choices were limited and the outlook could be serious. Over time, researchers began to suspect that the type of fat mattered, not just the amount. They noticed something striking in babies with intestinal failure: switching to fat blends containing fish oil could sometimes reverse liver damage that was already underway [4]. That observation sparked a broader question—could a smarter fat blend prevent liver trouble in the first place, across all premature babies on intravenous nutrition [5]?

To understand why the type of fat matters, it helps to picture what the liver has to do. The liver makes bile, a fluid that helps digest fat and carries away waste. When a baby is fed through a vein for a long time, the liver is doing this job without the normal rhythm of milk arriving in the gut, and certain ingredients in older, soybean-only fat blends appear to irritate liver cells and slow the flow of bile. Bile then backs up, which is what cholestasis means. Doctors also came to suspect that some plant-derived compounds in pure soybean oil, together with an imbalance between two families of fats known as omega-6 and omega-3, added to the inflammation and stress on the liver [6]. If that was true, then changing the recipe of the fat—not just how much was given—might spare the liver.

SMOFlipid was designed with that idea in mind. Its name comes from its four ingredients: Soybean oil, Medium-chain triglycerides, Olive oil, and Fish oil. The fish oil supplies omega-3 fats, the kind linked to calming inflammation; the olive oil and the balanced recipe reduce some of the substances in pure soybean oil thought to irritate the liver; and the blend carries more vitamin E, a natural antioxidant [6]. In theory, it should be gentler on a newborn's liver. But theory is not proof, and for years families and doctors had only small studies and blood-test results to go on. This review set out to gather all the reliable evidence in one place.

What the Researchers Did and Found

The researchers combined the results of 20 carefully conducted trials in which newborns were randomly assigned to receive either SMOFlipid or an older fat blend—the fairest way to compare two treatments. The babies came from many countries and ranged from extremely premature to nearly full-term, and they received intravenous nutrition anywhere from about one week to two months [1].

The clearest result was about the liver. Babies given SMOFlipid were significantly less likely to develop cholestasis—a roughly 35% lower risk—and this finding was remarkably consistent from trial to trial [1]. Importantly, the protection was strongest in exactly the babies who need it most: the most premature infants (born before 28 weeks) and those who stayed on intravenous nutrition for two weeks or longer, who face the greatest cumulative strain on the liver. The trial that most directly studied this liver complication in the tiniest babies pointed the same way [7].

There was a second, smaller piece of good news. In babies born before 28 weeks, SMOFlipid was linked to a slightly lower rate of a heart condition called patent ductus arteriosus, in which a blood vessel that should close after birth stays open [8]. This effect was modest and appeared only in the most premature group, so doctors treat it as a promising hint rather than a settled fact.

One detail is worth explaining, because it shows how carefully the researchers worked. They did not simply count up results and stop; they tested how solid each finding was. For the liver benefit, they repeated the analysis after removing each trial one at a time to make sure no single study was driving the result—and the conclusion held steady every time. They also checked for the common problem of studies with disappointing results never getting published, which can make a treatment look better than it really is, and found no sign of it. Those extra checks are part of why the liver finding can be trusted more than a single small study on its own.

Just as important is what the review did not find. SMOFlipid did not clearly change the chances of chronic lung disease, serious bowel infection, bleeding in the brain, eye disease of prematurity, infection in the bloodstream, or survival, and it did not shorten the hospital stay [1]. An earlier hope that fish-oil blends might protect babies' eyes was not borne out here [9]. This is honest, useful information: the blend helps the liver, but it is not a cure-all for the many challenges of being born early.

What This Means for Your Baby

It also helps to know that this liver problem is usually temporary and closely watched. The care team checks your baby's liver with routine blood tests, often once or twice a week, so that any early sign of cholestasis is caught and addressed. In most babies, once the intestine matures and full milk feeds take over, the liver strain eases and the jaundice fades. The fat blend is one tool among several the team uses to keep that strain as small as possible in the meantime.

If your baby is receiving intravenous nutrition, there is a good chance the fat blend is a fish-oil-containing product like SMOFlipid, chosen specifically to lower the risk of the liver complication that long-term intravenous feeding can cause. That is a reassuring, evidence-based choice, especially for the smallest and most premature babies and those expected to need nutrition through a vein for a while. It is fair to ask your care team which fat blend your baby is receiving and why.

At the same time, it helps to keep expectations realistic. This nutrition choice is one of many pieces of your baby's care. It has not been shown to change lung, eye, brain, or survival outcomes—those depend on the whole of neonatal intensive care. Your team will still watch your baby's liver with regular blood tests and will work toward starting milk feeds as soon as it is safe, because getting your baby onto full feeds is the surest way to protect the liver and bring the intravenous nutrition, and its risks, to an end [10].

What Researchers Are Working On Next

The biggest open question is the long term. Because these trials followed babies only through their early hospital course, no one yet knows whether a gentler fat blend leads to better development years later—whether it helps thinking, movement, and learning as children grow. Future studies will need to follow children to age two and beyond, and to compare SMOFlipid head-to-head against specific alternatives rather than a mix of older products [11]. For now, families can take encouragement from a clear, consistent finding: a thoughtfully designed nutrition fat is quietly protecting the livers of the most vulnerable newborns, buying them time and safety while their own bodies catch up.

References

  1. He T, Huang J, Ren D, Yang S. Impact of SMOFlipid on Clinical Outcomes in Neonates Receiving Parenteral Nutrition: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Br J Hosp Med. 2024. doi:10.12968/hmed.2024.0303 ↩
  2. Moltu SJ, Lapillonne A, Iacobelli S. Parenteral Nutrition in Premature Infants. In: Textbook of Pediatric Gastroenterology, Hepatology and Nutrition. Springer; 2021:87–101. doi:10.1007/978-3-030-80068-0_7 ↩
  3. Bell EF, Hintz SR, Hansen NI, et al. Mortality, In-Hospital Morbidity, Care Practices, and 2-Year Outcomes for Extremely Preterm Infants in the US, 2013-2018. JAMA. 2022;327(3):248–263. doi:10.1001/jama.2021.23580 ↩
  4. Diamond IR, Grant RC, Pencharz PB, et al. Preventing the Progression of Intestinal Failure-Associated Liver Disease in Infants Using a Composite Lipid Emulsion: A Pilot Randomized Controlled Trial of SMOFlipid. JPEN J Parenter Enteral Nutr. 2017;41(5):866–877. doi:10.1177/0148607115626921 ↩
  5. Kapoor V, Malviya MN, Soll R. Lipid emulsions for parenterally fed preterm infants. Cochrane Database Syst Rev. 2019;6:CD013163. doi:10.1002/14651858.CD013163.pub2 ↩
  6. Goulet O. An Overview of Parenteral Nutrition from Birth to Adolescence Based on a Composite Fish Oil Containing Lipid Emulsion and a Pediatric Amino Acid Solution. Nutrients. 2024;16(3):440. doi:10.3390/nu16030440 ↩
  7. Repa A, Binder C, Thanhaeuser M, et al. A Mixed Lipid Emulsion for Prevention of Parenteral Nutrition Associated Cholestasis in Extremely Low Birth Weight Infants: A Randomized Clinical Trial. J Pediatr. 2018;194:87–93.e1. doi:10.1016/j.jpeds.2017.11.012 ↩
  8. Hamrick SEG, Sallmon H, Rose AT, et al. Patent Ductus Arteriosus of the Preterm Infant. Pediatrics. 2020;146(5):e20201209. doi:10.1542/peds.2020-1209 ↩
  9. Vayalthrikkovil S, Bashir RA, Rabi Y, et al. Parenteral Fish-Oil Lipid Emulsions in the Prevention of Severe Retinopathy of Prematurity: A Systematic Review and Meta-Analysis. Am J Perinatol. 2017;34(7):705–715. doi:10.1055/s-0036-1597131 ↩
  10. Costa S, Cocca C, Barone G, et al. Growth of Head Circumference and Body Length in Preterm Infants Receiving a Multicomponent vs a Soybean-Based Lipid Emulsion: A Randomized Controlled Trial. JPEN J Parenter Enteral Nutr. 2021;45(1):94–101. doi:10.1002/jpen.1968 ↩
  11. Djuricic I, Calder PC. Beneficial Outcomes of Omega-6 and Omega-3 Polyunsaturated Fatty Acids on Human Health: An Update for 2021. Nutrients. 2021;13(7):2421. doi:10.3390/nu13072421 ↩