Wound healing is a complex and multifaceted process. However, one often underestimated area is the role nutrition plays in the outcomes of these patients. Accordingly, this author outlines important biochemical concepts along with practical clinical components of incorporating nutrition principles into a wound healing protocol.
As a former nutritionist (prior to podiatry school), I worked in a hospital as a dietitian and helped to address the different nutritional needs of patients. While I cannot say I was well versed in wound care at that time, I did provide counsel on proper dietary goals for patients with hypertension, diabetes, renal impairment, cardiac conditions, etc. Even then, motivating patients to take ownership and be responsible for their dietary needs/constraints posed a challenge, let alone the patients understanding the basics of nutrition and the importance of these tenets to their well-being. Now, as a podiatrist dealing with wound care daily, I find that the challenge is even greater when it comes to educating people regarding their weight, the effects of diabetes on the health of their feet, the importance of exercise and tight glucose control.
Optimal wound healing requires adequate nutrition.1-4 Lack of proper nutrition will have an adverse effect on the intricate process of wound healing. Poor dietary control can quickly turn a “normal” wound into a chronic non-healing wound. The anabolic phase of wound healing, marked by the arrival of stress hormones, macronutrients, and micronutrients into the wound, helps with the creation of new tissue. However, if the catabolic phase drags on too long, a phenomenon known as protein energy malnutrition can occur.5 This begins a negative cycle whereby the body will send extra protein to a wound site, but, as a negative consequence, other organs may not receive enough protein and lean muscle mass may begin to break down. This ultimately will cycle back to delayed wound healing.5
How Nutritional Deficiencies Can Affect The Progression Of Wound Healing
Before delving into the intricacies of nutrition and malnutrition, here are some key points to consider about the progression of wound healing, which consists of three main phases.
The inflammatory phase begins the process and can last for up to six days from the initial injury.2 In this phase, platelets and coagulation factors will form a fibrin clot over the area to try to achieve hemostasis as well as a protective barrier. Neutrophils and macrophages also try to remove bacteria from the wound.2 The proliferative phase starts about three to five days post-injury but can last upward of three weeks. This stage is marked by the beginning of fibroblast activity, angiogenesis and epithelialization.2 Collagen also begins to lay down in this phase, beginning the process of wound contraction. Remodeling, or the final phase, can last up to two years and provides the wound with collagen maturation, resulting in a more stable, healing wound with increased tensile strength and scar formation.2
Chronic wounds, however, have a prolonged inflammatory phase with low levels of growth factors and increased bioburden.2 Nutritional deficiencies can severely impede the normal pathway for healing, delaying it by decreasing wound tensile strength and increasing infection rates.3
Normal metabolism can be critical when considering both the surgical patient as well as the patient with a diabetic wound.4,5 One of the critical elements necessary for healing is energy, which is received via carbohydrates, fats and proteins.2 Although energy is most efficiently processed from carbohydrates and fats, protein is by far the most important of the required dietary components for a healing wound because it helps to repair damaged tissue.2
Understanding The Importance Of Protein In Wound Care
It is important to increase protein in one’s diet while trying to heal a wound and not allow the loss of lean body mass. This can be deleterious to one’s general health as well as to the wound healing process. A loss of more than 15 percent of lean body mass will impair wound healing while a 30 percent loss of lean body mass can lead to the development of spontaneous wounds such as pressure ulcers and even wound dehiscence.2,5
It is important to remember that proteins are the “building blocks” or the tools used to create new tissue. With normal hormone activity, the body uses nearly all protein byproducts for synthesis and not energy. Carbohydrates and fats enter the energy system and can be stored for later energy use. However, most consumed proteins enter the synthesis process, not the energy cycle.6 Protein makes up the critical cell structure in muscle/organs/red blood cells and connective tissue.5 Proteins also include enzymes and antibodies that maintain immune functions. Skin is composed mainly of protein collagen.
A healthy adult requires 0.8 g of protein per kilogram of body weight per day with the upper end of recommended intake falling between 1.2 to 2.0 grams per kilogram.7 Stressed patients (i.e. patients with wounds) require almost double the protein intake at 1.5 grams of protein/kg of body weight.8 The increased needs originate from both the demand for protein synthesis and increased loss of amino acids abnormally channeled for fuel and energy. Good sources of protein include lean meats, eggs, lentils, beans, peanut butter and fish to name a few.8 It is easy to appreciate the importance of proteins with respect to wound healing.
What Are The Roles Of Carbohydrates And Fats In Wound Healing?
In addition to protein, there are other dietary essentials to aid in wound healing. Carbohydrates tend to get a bad rap of late in the diet world but are essential in the diet of someone trying to heal a wound. Remember that proteins can be used for energy but are better served in the anabolic process so carbohydrates may fill that role for energy use. Wounds require energy for, among other things, collagen synthesis.8
Glucose is the major fuel used to generate cellular energy in the form of adenosine triphosphate (ATP), which drives the wound healing process. The use of glucose to generate adenosine triphosphate can be inefficient but it is the caloric contribution of glucose which is essential for preventing the depletion of proteins. Sometimes the liver and lean muscle mass are called upon for gluconeogenesis but this can result in excess glucose in the blood as well as depletion of amino acids and protein. When this occurs, the excess glucose significantly impairs the body’s attempt to heal a wound whereby patients with tightly controlled glucose show better outcomes in terms of healing.9
While it is still not completely understood, a buildup of advanced glycation end products within the tissues may be responsible for delays in healing.1 Patients with diabetes can therefore suffer from a decreased but prolonged inflammatory phase that results in delayed deposition of matrix components as well as delayed epithelialization and decreased collagen formation.1 This in turn will result in decreased wound remodeling and delayed closure.
Hyperglycemia can also interfere with the transport of ascorbic acid into certain cells, namely leukocytes and fibroblasts. Structurally, ascorbic acid and glucose are similar so there may be a competitive inhibition of ascorbic acid, which in turn may help explain the decreased early inflammatory response, which increases the delay in healing. Also, wound infection rates may be higher in those with diabetes because of immunocompromise so it is important for practitioners to discuss sound nutritional goals early in the treatment plan to try to bring these factors under control quickly. Again, achieving normal glucose control is perhaps the most important goal for successful wound healing in a patient with diabetes.1
Fats are another essential macronutrient necessary for good wound healing. Demling has suggested that the demand for fatty acids likely increases when there is a wound.10 Linoleic and arachidonic acids are two fatty acids that have been recognized as essential for prostaglandin synthesis. Phospholipids are also necessary for wound healing in that they are the key components of basement membranes while prostaglandins are important for cellular metabolism and inflammation. Researchers have studied omega-3 fatty acids for possible benefits in wound healing but they do not appear to be as structurally strong as other fatty acids.11 Omega-3 fatty acids do show benefit however, in propelling stronger immunity in the host, thereby decreasing infection rates and improving healing.11
Along with cell membrane formation, one needs extra fats to power a wound to heal. Lipid components are responsible for tissue growth and wound remodeling including collagen and extracellular matrix production. Animal fats including cheeses, butter and meat sources are excellent sources of fats, but other sources include fatty fish, avocado and nuts.7,10
What About Micronutrients?
Vitamins and minerals, also known as micronutrients, are also key contributors to good wound healing. Whereby there are several micronutrients that can have a positive impact on wound healing, vitamins C, A and the mineral zinc appear to be the most crucial.2,4,8 Vitamin C is an important antioxidant. It increases the strength of the wound as it heals and helps with the creation of collagen in the skin. Vitamin C also plays an important role in the development of new blood vessels and helps with iron absorption. As little as 200 mg of vitamin C daily can increase wound healing.2,8
Back in 1940, Crandon and coworkers studied Vitamin C and its relationship to scurvy.12 Interestingly, Crandon and his associates first noticed the poor signs of healing with a vitamin C deficiency in a human experiment that he conducted on himself. He consumed a diet lacking vitamin C for three months and noted no significant impact on wound healing other than fatigue. However, after a six-month period, Crandon biopsied a poorly healing surgical incision. The biopsy revealed no signs of healing with little collagen and few fibroblasts. He subsequently placed himself on a diet rich in Vitamin C (one gram per day) and another biopsy revealed increased collagen and capillary formation. Accordingly, Crandon and coworkers determined that a deficiency of Vitamin C can cause minimization of collagen deposition along with decreased angiogenesis.
Vitamin C deficiency, while crucial for strong wound healing, also increases one’s immunity in protection against infection. If infection does occur in a host with Vitamin C deficiency, the infection also appears to be more severe.2,8 The thought is that the decrease in Vitamin C may be associated with decreased collagen synthesis as well as the host’s inability to contain and localize the infection while also inhibiting neutrophil activity within the wound. Good sources of Vitamin C include most citrus fruits, tomatoes, green leafy vegetables and potatoes.8
Vitamin A is another crucial antioxidant. It helps ward off infection and can control the overall inflammatory response.8 Vitamin A stimulates epithelialization and collagen deposition by fibroblasts. Red fruits, fish, eggs and dark green vegetables are excellent sources of vitamin A. Importantly, vitamin A is fat soluble so toxicity can occur in overconsumption as opposed to vitamin C, which is water soluble. Excess Vitamin C is easily excreted if one ingests too much.8
Other vitamins believed to aid in wound healing include the B vitamin complex. However, the thought process with B vitamins is that, although they are helpful in wound healing, the effects are more notable for the increase in infection resistance and strengthening host immunity rather than for direct wound healing.13 Fat soluble vitamin E is also cited for its role in stabilizing membrane integrity and for “scavenging” a wound for excess free radicals. Free radicals damage collagen, proteins and lipids that are the key components for healing. In necrotic or ischemic wounds, there can be an abundance of free radical formation, which can also result in a depletion of these so-called scavengers like vitamin E.14-16
The mineral zinc helps the body synthesize proteins and develop collagen. It is involved in DNA synthesis, protein synthesis and cell proliferation. In the hypermetabolic state, there is an increase in urinary loss of zinc, which can result in decreases in the rate of epithelial cell proliferation, wound strength and collagen strength, thereby prolonging wound healing.17
Other minerals, notably magnesium, copper and iron, can be essential for healing as well. Magnesium is crucial for wound repair and is a cofactor for many enzymes involved in protein and collagen synthesis. In general, most fruits and vegetables are excellent sources of micronutrients.8 One should also note that food supplements and drinks on the market may help provide increased proteins, carbohydrates and micronutrients for elderly patients who have poor nutritional intake.
Assessing Findings From Lab Tests
Lastly, there are certain lab values that may aid in determining the nutritional status of one’s patient with respect to wound healing.
Along with CBC and basic chemistry panels, serum albumin is the most helpful test. Any value of serum albumin dropping below 3.5 mg/dl is a good prognosticator of poor healing.18 Also, a low body weight, less than 85 percent of an ideal body weight, is a risk factor as is a greater than five percent loss of body mass over one month.19 A low transferrin value can also be a risk indicator for poor healing.20
In conclusion, when it comes to wound care, assessing nutritional status, questioning patients on nutrition and educating them on proper nutrition can play important roles in the overall management of a wound. Hopefully, by taking a few of these concepts into account, we can all become better equipped to deal with the many of these cases involving chronic wounds in patients with inadequate or poor nutrition.
Dr. Rosenthal is a Fellow of the American College of Foot and Ankle Surgeons and a Fellow of the American Society of Podiatric Surgeons. She is in private practice with Foot and Ankle Specialists of the Mid-Atlantic in Hagerstown, Md.
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