By Sara Glanz, MS, RD, LD, CNSC
Intravenous lipid emulsions (ILEs) were first introduced in 1961. Back then, the only option was a 100% soybean oil emulsion. But over the past six decades, ILEs have evolved to include less and less soybean oil. In fact, the latest ILEs don’t include any soybean oil at all. So, what’s the scoop on these new products?
What’s on the market?
Currently in the United States, there are five ILEs approved by the Food and Drug Administration (FDA).
- Intralipid®: 100% soybean oil1
- Nutrilipid®: 100% soybean oil2
- Clinolipid®: 80% olive, 20% soybean oils3
- SMOFlipid®: 30% soybean, 30% medium-chain triglycerides, 25% olive, 15% fish oils4
- Omegaven®: 100% fish oil5
A few words about fatty acids
When it comes to the clinical benefits or drawbacks of ILEs, it all boils down to the types of fatty acids that make up the emulsion. Linoleic acid, an omega-6 fatty acid with proinflammatory properties, makes up approximately 50% of soybean oil.6 In contrast, fish oil predominantly consists of omega-3 and omega-9 fatty acids. These fatty acids have anti-inflammatory characteristics. Approximately 3% or less of fish oil is sourced from linoleic acid.6
What’s wrong with soy-based lipids?
Soybean oil based ILEs have been in use for over sixty years. In fact, many healthcare facilities exclusively use these ILEs for patients who require parenteral nutrition. So, what’s the problem?
Soy-based ILEs have a 7:1 ratio of omega-6 to omega-3 fatty acids.7 This means there seven times more proinflammatory fatty acids compared to anti-inflammatory fatty acids. The end result is an environment conducive to inflammation and immunosuppression. In fact, researchers believe that many of the undesirable clinical complications associated with parenteral nutrition may be due to the proinflammatory profile of soy-based lipids.7
Research for alternative ILEs is in the early stages. Therefore, many studies are small and short in duration. The research that has been done primarily focuses on biomarkers (like, serum levels of specific fatty acids, liver function enzymes, and inflammatory markers) or clinical outcomes.
Generally speaking, patients who receive alternative ILEs compared to soy-based products have increased blood levels of omega-3 fatty acids and reduced levels of liver function enzymes. However, it’s worth noting that some studies could not identify a statistically significant difference between the two ILEs with regard to these and other parameters.8-12
When it comes to clinical outcomes, the research doesn’t distinguish a clear benefit of any ILE.8,12 Although serum biomarkers may be improved with the use of alternative lipids, this doesn’t (yet) translate into any statistical difference in clinical outcomes.
There is certainly a gray area when it comes to choosing the best ILE product. Soy-based emulsions have a bad rap and the biochemistry to prove it. However, newer and more expensive alternative ILEs have yet to prove their superiority. So, what’s a dietitian to do?
Stay tuned. More research is surely coming, and longer-term studies may turn the tides in favor of alternative ILEs. In the meantime, use soy-based lipids judiciously and according to established guidelines. Interested in learning more and hearing the latest research in infants and neonates? Check out our on-demand CPEU webinar, “What’s New with IV Lipids?”.
Sara Glanz, MS, RD, LD, CNSC worked as a traveling dietitian for Dietitians On Demand for two years before joining the team as the corporate dietitian. In this role, she has championed the continuing education program to empower dietitians everywhere to achieve their professional goals.
Dietitians On Demand is a nationwide staffing and recruiting company for registered dietitians, specializing in short-term, temporary and permanent-hire positions in acute care, long term care and food service positions. We’re dedicated to dietitians and helping them enhance their practice and excel in the workplace. Check out our job openings, request your coverage, or visit our store today!
Vanek VW, Seidner DL, Allen P, et al. A.S.P.E.N. position paper: clinical role for alternative intravenous fat emulsions. Nutr in Clin Prac. 2012;27(2):150-192.
Calder PC, Waitzberg DL, Klek S, Martindale RG. JPEN. 2020;44(1):S21-S27.
Abbasoglu O, Hardy G, Manzanares W, Pontes-Arruda A. Fish oil-containing lipid emulsions in adult parenteral nutrition: a review of the evidence. JPEN. 2019;43(4):458-70.
Donoghue V, Schleicher GK, Spruyt MGL, et al. Four-oil intravenous lipid emulsion effect on plasma fatty acid composition, inflammatory markers and clinical outcomes in acutely ill patients: A randomised control trial (Foil fact). Clin Nutr. 2019;38:2583-91.
Klek S, Chambrier C, Singer P, et al. Four-week parenteral nutrition using a third generation lipid emulsion (SMOFlipid) – A double-blind, randomised, multicentre study in adults. Clin Nutr. 2013;32:224-31.
Cai W, Calder PC, Cury-Boaventura MF, et al. Biological and Clinical Aspects of an Olive Oil-Based Lipid Emulsion—A Review. Nutrients. 10, 76; doi:10.3390/nu10060776
Dai YJ, Sun LL, Li MY, et al. Comparison of formulas based on lipid emulsions of olive oil, soybean oil, or several oils for parenteral nutrition: a systematic review and meta-analysis. Adv Nutr. 2016;7:279-86.