As health care professionals, we are all aware that good nutrition is necessary for wound healing, and that poor nutrition impedes wound healing. But do you know why specific dietary components are so important for healing? In this article, we’ll review the specific dietary macronutrients and the important role they play in the wound healing process.
Carbohydrates (predominantly in the form of glucose) provide the necessary energy required for tissue repair and regeneration. Carbohydrates are also needed for phagocytosis, the process by which cells engulf material (such as bacteria) to destroy it. Carbohydrates are ‘protein sparing’ meaning that, in the absence of adequate energy from foods taken in, the body converts fat and protein to be used as sources of energy. When protein stores are not replaced, protein deficiency will occur, which will slow wound healing. Therefore, a diet comprised of an adequate amount of carbohydrates is vital in order to maximize wound healing.
We learned in biology that amino acids are the building blocks of proteins. There are 22 amino acids. Nine of these amino acids are essential, meaning that they cannot be manufactured by the body and must be obtained through diet. Protein is necessary for tissue regeneration and repair. When our diets are deficient in protein, all three phases of wound healing may be impaired. Without adequate stores of protein, angiogenesis, collagen synthesis, granulation tissue formation and remodelling may all be significantly impaired. Low protein levels will also negatively affect immune function, including antibody response time and phagocytosis. Protein deficiency also alters osmotic pressure, causing fluid to move from the blood vessels into the interstitium. Edema decreases the ability of oxygen to diffuse into the affected area. In addition, the pressure created by edema can diminish blood flow within the affected area, which further decreases the available oxygen and allows metabolic waste products to build up.
Although protein deficiency is most commonly caused by inadequate protein intake, wounds themselves can also be a significant source of protein loss through wound drainage. Patients who have large surface area burns or wounds that are heavily draining are particularly prone to protein deficiency due to the amount of protein lost through wound drainage. Because protein deficiency affects all phases of healing, it is crucial that patients have sufficient protein intake from the beginning of wound healing until wound closure has been achieved. As you may recall, protein is made up of 16% nitrogen, thus nitrogen excretion can be used to indicate protein status. Nitrogen balance occurs when the amount of nitrogen excreted equals the amount of nitrogen ingested. When more nitrogen is excreted than is ingested in the form of protein, a negative nitrogen balance exists. This occurs when the body uses stored proteins as its main source of energy. A positive nitrogen balance enhances wound healing, thus a high-protein diet may enhance wound healing.
These days, fats have garnered a bad reputation. However, fat is essential to healing. When carbohydrate sources are depleted, fat provides a necessary energy source to fuel the body. Fat is also needed to carry fat-soluble vitamins such as vitamins A, E and K, which are necessary for wound healing. Fat also provides insulation which helps with thermoregulation. Lastly, free fatty acids make up part of the cell membrane and are required to synthesize new cells.
As can be seen, the macronutrients are crucial for wound healing. Patients who are deficient in fat, protein and/or carbohydrates are likely to experience delayed wound healing. In part two of Nutrition and Wound Healing, we’lll discuss the important role of micronutrients in wound healing.
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Meyers, B (2008). Wound Management: Principles and Practice. 2nd edition. Pearson Prentice Hall. Upper Saddle River, New Jersey. pg. 197-98.
Nutritional Support. Wound Source. http://www.woundsource.com/patientcondition/nutritional-support