HMB Supplement Study: New ICU Inflammation Research

When a critically ill patient is admitted to an intensive care unit, their body enters a state of profound metabolic crisis — muscle proteins break down rapidly, inflammation surges, and the immune system struggles to keep pace. A newly published post-hoc analysis from Clinical Nutrition (Berger et al., 2026) offers intriguing evidence that a naturally occurring compound derived from the amino acid leucine — beta-hydroxy-beta-methylbutyrate, or HMB — may meaningfully alter the inflammatory and protein-synthesis landscape in this vulnerable population. While the findings are preliminary and require confirmation in larger trials, they add an important layer to our understanding of how targeted nutritional supplementation might support critically ill patients.

What This Study Found

This research was a secondary post-hoc analysis of a previously published randomized controlled trial (ClinicalTrials.gov: NCT03628365). Thirty-seven critically ill patients — with an average age of 65 years and high illness-severity scores (SAPS2: 48; APACHE II: 23) — were randomly assigned to receive either 3 grams of HMB per day or a placebo for a minimum of 10 days following ICU admission. Assessments were conducted on days 4 and 15 after admission, and blood samples were analyzed for a broad panel of cytokines, C-reactive protein (CRP), amino acids, urea, and creatinine. Whole-body amino acid production was tracked using stable isotope tracers — a highly precise measurement technique.

Among the study's most notable findings was the behavior of cytokines — the signaling proteins that orchestrate the immune response. Of the 37 cytokines measured, most declined by day 15 in both groups, which is expected as patients recover. However, 12 cytokines differed significantly between the HMB and placebo groups after the intervention period, with levels — including 7 pro-inflammatory cytokines — being notably higher in the HMB group (p < 0.05). At first glance, higher pro-inflammatory markers might seem concerning, but the researchers interpret this pattern as potentially reflecting a more efficient, appropriately regulated immune response rather than unchecked systemic inflammation.

On the amino acid front, whole-body production rates and extracellular pool sizes did not differ significantly between groups by day 15. The more striking differences emerged at the intracellular level. In the HMB group, intracellular concentrations of citrulline, glutamine, HMB itself, KMV (α-keto-β-methylvaleric acid), taurine, and tau-methylhistidine were all significantly elevated compared to placebo. Glutamine production and HMB production increased significantly more in the HMB group than in the placebo group. Additionally, the urea-to-creatinine ratio — a marker of protein catabolism — decreased significantly in the HMB group by day 15 (125 vs. 181; p = 0.002), suggesting a meaningful reduction in muscle protein breakdown.

Clinical Significance

The clinical implications of these findings, if confirmed in larger studies, could be substantial. Critical illness is characterized by an accelerated loss of skeletal muscle mass — a process called ICU-acquired weakness — that is associated with prolonged mechanical ventilation, longer hospital stays, and worse long-term functional outcomes. Any intervention that attenuates protein catabolism while supporting immune function is of considerable clinical interest.

The intracellular glutamine finding deserves particular attention. Glutamine is a conditionally essential amino acid that becomes severely depleted during critical illness. It plays a central role in immune cell proliferation, gut barrier integrity, and antioxidant defense. The study suggests that HMB supplementation may support endogenous glutamine synthesis at the cellular level — a pathway that standard nutritional support does not reliably address. As the authors note, this intracellular effect was observed despite no significant differences in whole-body or extracellular amino acid pools, underscoring how conventional blood measurements may miss important metabolic activity happening within cells.

The cytokine pattern also warrants careful interpretation. Researchers propose that the higher pro-inflammatory cytokine levels seen in the HMB group may reflect a more active, targeted immune response rather than excessive inflammation — a distinction that is clinically meaningful. In critical illness, an inadequate or dysregulated immune response is often more dangerous than a robust one. The study suggests HMB may help calibrate this response, though the mechanisms remain to be fully elucidated.

It is important to note that this was a post-hoc secondary analysis of a relatively small randomized trial (n=37). Post-hoc analyses are hypothesis-generating by nature and are subject to the limitations of multiple comparisons and reduced statistical power. The researchers themselves acknowledge these constraints. Larger, prospectively designed trials are needed before definitive clinical recommendations can be made.

Current Access and Compliance Context

HMB is commercially available as a dietary supplement and is already used in some clinical nutrition protocols, primarily for its well-documented effects on muscle protein synthesis in aging and exercise contexts. The leucine metabolite has a well-established safety profile, and the dose used in this study — 3 grams per day — is consistent with amounts used in prior human research.

In the ICU setting, nutritional supplementation compliance can be challenging due to the complexity of enteral and parenteral feeding regimens, gastrointestinal intolerance, and the rapidly changing clinical status of critically ill patients. In this study, participants received HMB for a minimum of 10 days, and measurements were taken under postabsorptive (fasting) conditions to isolate the metabolic effects of the supplement from acute feeding responses. This methodological rigor strengthens the reliability of the intracellular amino acid findings, though real-world ICU delivery of HMB may face additional logistical hurdles.

For practitioners interested in exploring HMB as part of a critical care nutrition strategy, consultation with an experienced clinical nutritionist or intensivist familiar with the evolving literature is strongly advised. The Peptide Association's physician directory can help connect patients and clinicians with qualified specialists.

What Patients Should Know

If you or a loved one is recovering from a serious illness, surgery, or prolonged hospitalization, the question of how to preserve muscle mass and support immune function during recovery is deeply relevant. Research like this study by Berger and colleagues highlights how nutritional compounds that were once considered purely performance-focused — like HMB — may have meaningful therapeutic applications in medical settings.

That said, patients and caregivers should approach this research with measured optimism. A post-hoc analysis of 37 ICU patients, while scientifically valuable, is not sufficient grounds to self-prescribe HMB supplementation during critical illness or recovery. Dosing, timing, interactions with medications, and individual metabolic status all matter significantly. Any supplementation strategy during or after critical illness should be discussed with and supervised by a qualified healthcare provider.

What this research does offer is a compelling signal: the body's intracellular metabolism responds to HMB supplementation in ways that standard nutritional markers may not capture, and this response appears to involve key amino acids like glutamine that are central to immune defense and tissue repair. As the science matures, HMB may become an increasingly recognized tool in critical care nutrition.

Conclusion

The 2026 post-hoc analysis by Berger, Viana, Engelen, and colleagues represents a meaningful step forward in understanding how HMB influences inflammation and intracellular amino acid metabolism in critically ill patients. The study suggests that HMB supplementation is associated with a distinct cytokine profile consistent with a more efficient immune response, a significant reduction in protein catabolism (as reflected by urea-to-creatinine ratios), and elevated intracellular concentrations of key amino acids — particularly glutamine. While larger prospective trials are needed to confirm these findings and establish clinical protocols, the evidence base supporting HMB's role in critical care nutrition continues to grow.

If you are interested in learning more about evidence-based peptide and nutritional therapies, or if you are seeking a qualified clinician who stays current with the latest research, visit peptideassociation.org/find-a-doctor to connect with a knowledgeable healthcare provider in your area.

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Medical Disclaimer: This article is intended for educational purposes only and does not constitute medical advice, diagnosis, or treatment. The information presented is based on published scientific research and should not be used as a substitute for professional medical guidance. Always consult a qualified healthcare provider before beginning any supplementation regimen, particularly in the context of serious illness or critical care. The Peptide Association does not endorse any specific product or treatment protocol.

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Citation (AMA format): Berger MM, Viana MV, Engelen MPKJ, et al. Does β-hydroxy-β-methylbutyrate (HMB) have an anti-inflammatory impact in critically ill patients? A secondary post hoc analysis of an RCT. Clin Nutr. 2026;(published online ahead of print). doi:10.1016/j.clnu.2026.106690. PMID: 42202485.