Proteins and amino acids are fundamental to optimal nutrition support in critically ill patients

Abstract

Proteins and amino acids are widely considered to be subcomponents in nutritional support. However, proteins and amino acids are fundamental to recovery and survival, not only for their ability to preserve active tissue (protein) mass but also for a variety of other functions. Understanding the optimal amount of protein intake during nutritional support is therefore fundamental to appropriate clinical care. Although the body adapts in some ways to starvation, metabolic stress in patients causes increased protein turnover and loss of lean body mass. In this review, we present the growing scientific evidence showing the importance of protein and amino acid provision in nutritional support and their impact on preservation of muscle mass and patient outcomes. Studies identifying optimal dosing for proteins and amino acids are not currently available. We discuss the challenges physicians face in administering the optimal amount of protein and amino acids. We present protein-related nutrition concepts, including adaptation to starvation and stress, anabolic resistance, and potential adverse effects of amino acid provision. We describe the methods for assessment of protein status, and outcomes related to protein nutritional support for critically ill patients. The identification of a protein target for individual critically ill patients is crucial for outcomes, particularly for specific subpopulations, such as obese and older patients. Additional research is urgently needed to address these issues.

Is transthyretin a good marker of nutritional status?

“…In this situation, the line between prognosis marker and nutritional marker is both too thin and too blurred. It might be best to use nitrogen balance to evaluate the adequacy of nutrition rehabilitation [53].…”

Parenteral Nutrition: Amino Acids

“…For more than four decades there has been a consensus—based on consistent, convincing animal and human metabolic data, N balance studies and clinical observational data—that critical illness increases human protein requirements [16,17,18,19,20,21,22,23,24]. Regrettably, suitably-powered hard clinical outcome trials to confirm or refute this physiologically plausible conclusion have not yet been carried out [2].…”

Considerations When Using Predictive Equations to Estimate Energy Needs Among Older, Hospitalized Patients: A Narrative Review

“…This may also be mediated by baseline nutritional risk status [26, 72]. The importance of adequate and optimal levels of protein intake during hospitalization is also being explored, and may influence clinical outcomes [26, 75, 76]. Although beyond the scope of this review, the estimation of protein requirements in hospitalized older patients has been examined by others [77-79] and certainly warrants further attention.…”