NUTRITION AND THE INTENSIVE CARE UNIT: Edited by Michael P. Casaer and Adam M. DeaneHMB and leucine supplementation during critical illness and recoveryBear, Danielle E.a,b; Rooyackers, Olavc Author Information aDepartment of Nutrition and Dietetics bDepartment of Critical Care, Guy's and St Thomas’ NHS Foundation Trust, London, UK cDepartment of Anesthesiology and Intensive Care, CLINTEC; Karolinska Instiitutet and Karolinska University Hospital, Huddinge, Sweden Correspondence to Dr Danielle E. Bear, Principal Critical Care Dietitian, St Thomas’ Hospital, Westminster Bridge Rd, London, SE1 7EH. Tel: +44 20 7188 9452; e-mail: [email protected] Current Opinion in Clinical Nutrition and Metabolic Care: March 2022 - Volume 25 - Issue 2 - p 88-92 doi: 10.1097/MCO.0000000000000809 Buy Metrics Abstract Purpose of review Skeletal muscle wasting is a serious consequence of critical illness, which may impact on long term physical and functional disability. To date, no intervention has been proven to reduce skeletal muscle wasting. Leucine and it's metabolite β-hydroxy-β-methylbutyrate (HMB) have been proposed as interventions. This review details the mechanism of action of both leucine and HMB, discusses the most recent research for both leucine and HMB and lastly discusses considerations for future research. Recent findings Only one study of leucine in critical illness has recently been published. This was a feasibility study where the physiological and muscle related outcomes were not reported to be feasible. Three studies on HMB have been reported recently with no effect seen on either muscle mass or strength. The main limitation in our understanding of the potential use of leucine or HMB on skeletal muscle wasting is the lack of mechanistic studies available in this population. Summary Mechanistic studies should be a priority before embarking on further randomized controlled trials related to this topic. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.