Nutrition, Anabolism, and the Wound Healing Process: An Overview

Robert H. Demling, MD

Disclosures

ePlasty. 2009;9:65-94. 

In This Article

Abstract and Introduction

Abstract

Objective:To develop a clear, concise, and up-to-date treatise on the role of anabolism from nutrition in wound healing. Special emphasis was to be placed on the effect of the stress response to wounding and its effect.
Methods: A compilation of both the most important and most recent reports in the literature was used to also develop the review. The review was divided into sections to emphasize specific nutrition concepts of importance.
Results: General and specific concepts were developed from this material. Topics included body composition and lean body mass, principles of macronutritional utilization, the stress response to wounding, nutritional assessment, nutritional support, and use of anabolic agents.
Conclusions: We found that nutrition is a critical component in all the wound healing processes. The stress response to injury and any preexistent protein-energy malnutrition will alter this response, impeding healing and leading to potential severe morbidity. A decrease in lean body mass is of particular concern as this component is responsible for all protein synthesis necessary for healing. Nutritional assessment and support needs to be well orchestrated and precise. The use of anabolic agents can significantly increase overall lean mass synthesis and directly or indirectly improves healing by increasing protein synthesis.

Introduction

Optimum nutrition is well recognized to be a key factor in maintaining all phases of wound healing. There are 2 processes that can complicate healing. One is activation of the stress response to injury, and the second is the development of any protein-energy malnutrition (PEM).

Any significant wound leads to a hypermetabolic and catabolic state, and nutritional needs are significantly increased. The healing wound depends on adequate nutrient flow (Fig 1). Of particular concern is the presence of any PEM, PEM being defined as a deficiency of energy and protein intake to meet bodily demands. PEM in the presence of a wound leads to the loss of lean body mass (LBM) or protein stores, which will in and of itself impede the healing process. Early aggressive nutrient and micronutritional feeding is essential to control and prevent this process from developing. PEM is commonly seen in the chronic wound population, especially the elderly, disabled, or chronically ill populations where chronic wounds tend to develop.[1–5]

Figure 1.

Balance between adequacy of macronutrients and net anabolism and catabolism and its impact on wound healing.

Hunter, in 1954, followed by Culbertson and Moore, identified the fact that a wound being a threat to human existence takes preference for the available nutrients to heal, especially amino acids, at the expense of the host LBM.[6–8] This process leads to an autocannibalism of available LBM to obtain the necessary amino acids for the required protein synthesis in the wound. If inadequate intake is present to keep up with needs, then PEM can develop. If inadequate glucose is available for the healing wound, proteins will break down into amino acids and through the alanine shunt lead to glucose synthesis by the liver. However, with severe losses of LBM, the host takes preference over the wound.[9–13]

This entire process is the result of the activation of the "stress response" to injury or wounding with its hormonal imbalance favoring body protein catabolism for substrate, needed for protein synthesis. There is also increased metabolic or calorie demand.[9–13]

There is a fundamental difference between the adequate intake seen in the unstressed patient and one where trauma or infection has activated the host stress response.[14,15] Starvation alone produces a self-protective hormonal environment, which spares LBM with more than 90% of calories obtained from fat.[14–16]

To optimize healing, a substrate that is more dependent on intake than on the bodily breakdown of protein needs to be available. Chronic wounds are more complicated because the biology of the healing process is significantly altered. However, a stress response is activated with any wound and any existing PEM will accentuate the already poor healing process.[17–19] For the above reasons, one cannot dissociate the normal process of healing from the nutritional status.

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