Nutrition And Wound Healing
By James Collier BSc (Hons) - Consultant in Nutrition and Moderator of Dietetics.co.uk
The importance of good nutrition in the healing of wounds and the promotion of health is widely accepted, but remains of low priority in health care and insufficient numbers of patients receive nutritional assessment. Practitioners need to become more knowledgeable about the role of nutrition in the promotion of wound healing.
Whereas good nutrition facilitates healing, malnutrition delays, inhibits and complicates the process (Williams and Leaper 2000). Nutritional support is fundamental to patient care and needs vary on an individual patient basis.
Before we examine the importance of nutritional assessment, we need to look at the nutrients which have key roles in the healing process:
Protein depletion can affect the rate and quality of wound healing (Gray and Cooper 2001). There is an increase in demand for protein in the presence of a wound, a requirement further increased in the event of sepsis or stress. Protein is required as part of the inflammatory process, in the immune response and in the development of granulation tissue. The main protein synthesised during the healing process is collagen, and the strength of the collagen determines wound strength.
Even short periods of low protein intake can result in significantly delayed wound healing. Protein inadequacy has also been shown to affect remodelling of the wound. In extreme cases of hypoalbuminaemia (i.e. low levels of the serum protein albumin) from long periods of insufficient protein intake, oedema may develop.
The amino acid arginine becomes essential during severe stress. It is abundant in the structure of collagen, and increases its tensile strength. Arginine metabolism is also related to the production of nitric oxide, which is bactericidal, and also aids wound healing through microvascular and haemodynamic changes.
As part of the healing process the body enters a hypermetabolic phase, where there is an increase in demand for carbohydrate. Cellular activity is fuelled by adenosine triphosphate (ATP) which is derived from glucose, providing the energy for the inflammatory response to occur. In the case of insufficient carbohydrate, the body breaks down protein to provide glucose for cellular activity (Gray and Cooper 2001). Therefore, in order to correct hypoalbuminaemia, carbohydrate is required as well as protein.
Fats have a key role in cell membrane structure and function. Certain fatty acids are essential, as they cannot be synthesised in sufficient amounts, so must be provided by diet. The role of essential fatty acids in wound healing is unclear, but as they are involved in the synthesis of new cells, depletion would certainly delay wound healing. It is debatable as to whether omega-3 polyunsaturated fatty acids (PUFAs) are more beneficial than omega-6 PUFAs. Omega-3s are anti-inflammatory, which aids wound healing, but may inhibit clotting which is disadvantageous (Williams and Leaper 2000).
B-Complex vitamins are co-factors or co-enzymes in a number of metabolic functions involved in wound healing, particularly in the energy release from carbohydrates.
Vitamin C has an important role in collagen synthesis, in the formation of bonds between strands of collagen fibre, helping to provide extra strength and stability. There is loads of evidence showing increased requirements for vitamin C during injury, stress and sepsis, but there is no evidence that mega dosing improves clinical outcomes (Gray and Cooper 2001).
Vitamin K is involved in the formation of thrombin, and deficiency in the presence of wounds could lead to a haematoma. Vitamin A is also involved in the cross-linking of collagen and the proliferation of epithelial cells.
Zinc is required for protein synthesis and is also a co-factor in enzymatic reactions. There is an increased demand for zinc during cell proliferation and protein secretion. Zinc also has an inhibitory effect on bacterial growth, and is involved in the immune response. Early studies suggest zinc supplementation, over and above that of the hospital diet, speed wound healing. Recent studies have shown no benefit, unless the patient has low serum zinc status (Gray and Cooper 2001).
Iron is a co-factor in collagen synthesis, and deficiency in iron delays wound healing. Copper is also involved in collagen synthesis.
The issue of supplementation in aiding wound healing is debatable. It is doubtless that a sufficient intake of all nutrients is needed, and that requirements may be raised during the healing process. This is often also the time when the patient, feeling unwell, has a poor appetite and dietary intake. There is some argument for supplementation with vitamin C and zinc in wound healing, but the evidence seems to point to being only when the patient is deficient in intake or has a low serum status. It is therefore necessary to check status of these two micronutrients along with other biochemical parameters in appropriate patients.
The ideal way to meet requirements of the above nutrients is by consuming adequate intake of normal foods (Perkins 2000). A normal hospital diet provides foods from all four food groups, but is often insufficient in quantity for patients with increased requirements. These patients may require supplementation with sip feeds, which are also fortified with an array of micronutrients. If a patient is consuming adequate amounts of food and sip feed supplements, it is doubtful that he/she will require specific vitamin or mineral supplements. In patients who have particularly stubborn wounds, a multi-vitamin and multi-mineral supplement may be administered.
Due to increased requirements, and the fact that many patients have a poor appetite and dietary intake, where oral sip feeds cannot help, artificial nutritional support may be initiated in the form of naso-gastric or gastrostomy feeding. Often patients are fed overnight by tube and encouraged to eat during the day, with the aim to wean them off tube feeding as nutritional status improves.
If a patients nutritional status is compromised, and they are unlikely to meet their requirements recovery will be delayed. Therefore nutritional assessment is vital to provide a baseline to work from. A good nutritional assessment involves the multidisciplinary approach including medical, nursing and dietetic staff. A number of assessment techniques may be employed including biochemical tests, weight, body mass index, anthropometry and dietary assessments. Nutritional Screening is an invaluable method of basic assessment done at nursing level. This is where a number of questions are asked concerning the patient's nutritional status to come up with a risk score, in order to identify possible risk of undernutrition. From this appropriate action can be initiated, which may include more detailed nutritional assessment.
It is obvious that nutrition plays a crucial role in wound healing, but there is little evidence that supplementing a patient's diet with specific nutrients in isolation improves clinical outcome. Further research is needed to identify the levels of supplements that will be of benefit to malnourished patients (Gray and Cooper 2001). Recommendations to patients with wounds should be to consume a healthy balanced diet, with sufficient quantities of energy and protein foods. All patients with wounds should have appropriate nutritional assessment through the multidisciplinary team.
Gray D, Cooper P. Nutrition and Wound healing: what is the link? Journal of Wound Care 2001 10(3) p86-89
Perkins L. Nutritional Balance in Wound Healing. Clinical Nutrition Update 2000 5(1), p8-10
Williams L, Leaper D. Nutrition and Wound Healing. Clinical Nutrition Update 2000 5(1), p3-5