New advances in stable tracer methods to assess whole-body protein and amino acid metabolismEngelen, Mariëlle P.K.J.; Ten Have, Gabriella A.M.; Thaden, John J.; Deutz, Nicolaas E.P.Current Opinion in Clinical Nutrition & Metabolic Care: September 2019 - Volume 22 - Issue 5 - p 337–346 doi: 10.1097/MCO.0000000000000583 ASSESSMENT OF NUTRITIONAL AND METABOLIC STATUS: Edited by Dwight E. Matthews and Kristina Norman Buy Abstract Author InformationAuthors Article MetricsMetrics Purpose of review Stable isotope methods have been used for many years to assess whole-body protein and amino acid kinetics in healthy conditions and in response to aging, exercise and (clinically stable) disease states. Recent findings In recent years, tracer research expanded to the anabolic response to feeding in critical illness and its use during acute metabolic stressors. Furthermore, new isotope approaches and tracer insights have been obtained. In the postabsorptive state, the novel tracer pulse approach has several advantages above the established continuous tracer approach because of the metabolic information that can be obtained, easy applicability, and low tracer costs. The use of bolus versus sip-feeding approaches to assess the anabolic response to a meal is dependent on the research question and its feasibility. Promising new tracer approaches have been developed to measure the anabolic capacity, and protein digestibility and absorption. Advances have been made in the field of mass spectrometry in low enrichment analysis. Summary Novel tracer approaches are available that can more readily be used in critical illness and during acute metabolic stressors. Besides the use of tracer application in various clinical conditions, more research is needed on how to incorporate isotopes on an individual level. Department of Health and Kinesiology, Center for Translational Research in Aging & Longevity, Texas A&M University, College Station, Texas, USA Correspondence to Mariëlle P.K.J. Engelen, PhD, Department of Health and Kinesiology, Center for Translational Research in Aging & Longevity, Texas A&M University, College Station, TX, USA. Tel: +1 979 220 2282; fax: +1 979 862 3244; e-mail: email@example.com Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.