ESPEN Conference 2025 Summary: Protein Dosing in the ICU

This is a summary of Dr. Arthur van Zanten’s presentation at ESPEN 2025.

Note, this information is a summary of information presented at the 2025 ESPEN conference in Prague. ESPEN guidelines do sometimes differ from ASPEN guidelines, so keep that in mind.

Critical Illness

• Lipid metabolism in ICU patients is disrupted (free fatty acids metabolism in the mitochondria are hindered, making fat can accumulate in the liver)

• Propofol and high fat from EN and PN can cause steatosis and fat infiltration in the muscles

• ICU patients are very vulnerable to over-feeding because of this

Autophagy is the body’s cleaning system, used to kill off and recycle dead cells

• In critical illness, autophagy can be suppressed

• Over-feeding can down-regulate autophagy, which is bad

The Microbiome

• The gut microbiota is disrupted in critical illness (gut dysbacteriosis)

• More research is needed in this area, to determine how long this lasts, and what to do about it

Carbohydrate Metabolism

• Endogenous production of glucose is not shut off during critical illness and feeding, meaning the liver is still producing glucose even though the body is in a fed (not fasted) state. This leaves ICU patients vulnerable to overfeeding 

• Dr. van Zanten recommends increasing energy by 25% per day of ICU stay, so the patient meets 100% of estimated needs by day 4 (see photo at the bottom of this page)

Protein

• • The target protein trial published in JAMA showed no benefit of increased protein enteral feeding

  • Mitochondrial dysfunction causes low production of ATP, which creates an “energy crisis” of the cells, preventing the metabolism and use of protein

  • Absorption and digestion of protein isn’t the issue for ICU patients; rather, the incorporation of amino acids into muscle proteins is much lower (substrate is available but not used = anabolic resistance) 

  • Optimal protein 0.9-1.6 g/kg per day

  • ASPEN guidelines up to 2.0 g/kg are too high

  • ESPEN recommends 1.3 g/kg as a mid-range target

  • Best outcomes are when protein intake is low day 1-3 of ICU stay, and once the metabolism recovers (days 4+), protein is increased. In other words, progressive protein intake

  • Dr. van Zanten recommends no protein supplements in the first stage of critical illness (day 1-3 ICU stay)

Takeaways

• Critically ill patients can’t metabolize or process carbohydrates, fats, and proteins like other patients

• Individualize nutrition and make feeding phase-specific (future applications include using biomarkers such as urine-to-creatinine ratio to determine the phase of critical illness your patient is in)

• Dr. van Zanten suggests 1.85 g/kg protein per kg of lean body mass (note this is not a formal guideline, more research is needed). It is interesting to think about how we can target protein intake to each patient, once we have better technology to differentiate lean vs. fatty body mass in the ICU

Now, go read these articles:

Personalized nutrition therapy in critical illness and convalescence: moving beyond one-size-fits-all to phenotyping and endotyping

Personalized nutrition therapy in critical care: 10 expert recommendations

Nutrition therapy and critical illness: practical guidance for the ICU, post-ICU, and long-term convalescence phases