Nutrition 411: The Facts about Vitamin C and Wound Healing
Why is Vitamin C Associated with Wound Healing?
Vitamin C has many physiologic functions in the human body. It is often aligned with wound healing because of its role in collagen formation. Vitamin C is a co-factor in proline and lysine hydroxylation, a necessary step in the formation of collagen. Hydroxyproline and hydroxylysine are essential for stabilizing the triple helix structure of collagen with strong hydrogen bonds and crosslinks. Without this stabilization, the structure disintegrates rapidly.1 Vitamin C also provides tensile strength to newly built collagen; otherwise, new tissue could not stretch without tearing. Tensile strength is important in pressure ulcer healing because healed pressure ulcers are susceptible to future skin breakdown. Vitamin C also is required for proper immune system function, a consideration in patients with open wounds. Other chief functions of vitamin C include: • antioxidant to inhibit damage to body cells • anti-inflammatory • necessary for the synthesis of carnitine, a molecule essential for the transport of fat to mitochondria • plays a role in the synthesis of the neurotransmitter norepinephrine • protects iron in the intestines from oxidation and promotes absorption • protects vitamin E in the blood from oxidation and may recycle it to its active form.
What are the Daily Requirements for Vitamin C?
The dietary references intakes (DRI) for nutrients are determined by the National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. Each DRI includes a recommended dietary allowance (RDA) and an upper limit (UL). The RDA may be used as a goal for individual intake. RDAs are set to meet the needs of almost all individuals (97% to 98%) in a group.2 It is important to note that the RDAs are based on healthy people. The UL represents the maximum daily intake likely to pose no risk of adverse effects. For vitamin C, the RDA for most women and men per day is 70 mg and 90 mg, respectively. The complete DRI for vitamin C is shown in Table 1.
What Happens When Intake of Vitamin C is Deficient?
The deficiency state of vitamin C is called scurvy. The clinical manifestations of scurvy are diverse and affect many of the body’s systems. Symptoms range from systemic conditions such as fatigue, weakness, and malaise to red, swollen gums and fragile, easily ruptured capillaries.3
Which Foods Contain Vitamin C?
Most people recognize citrus fruits, such as oranges and grapefruits, as good sources of vitamin C. Many other sources provide more than 20% of the RDA in a typical serving, including guava, kiwi, red sweet pepper, strawberries, papaya, broccoli, green pepper, vegetable juice cocktail, kohlrabi, Brussels sprouts, cantaloupe, pineapple, kale, edible pea pods, sweet potato, and mango. It is important to recognize that water-soluble vitamins like vitamin C are not stored in the body and must be replenished daily. Vitamin C is the most unstable of all water-soluble vitamins — cooking, handling, and processing affect its content in food. The vitamin is easily destroyed by oxygen, alkalis, and high temperature; it also reacts with the metallic ions of iron and copper. Patients should be encouraged to consume at least one daily serving of a food that is a good source of vitamin C, such as orange juice.
Should Patients with Pressure Ulcers Be Given Routine Vitamin C Supplementation?
The answer to the question of vitamin C supplementation elicits many different opinions and practices. When looking strictly at the evidence from well-designed studies, information is scant to support the theory that vitamin C supplementation above the RDA improves wound healing. An often-cited study4 divided 88 patients into two randomized groups: the first group received ascorbic acid supplementation of 500 mg twice per day while the control group received 10 mg twice per day. Using wound closure rate as the outcome measurement, the study concluded that ascorbic acid did not speed up wound healing. According to most of the agencies and groups that publish practice guidelines, supplementation is not necessary unless a deficiency is suspected. That said, many facilities and protocols continue to call for routine supplementation.
Why Do Facilities Provide Supplements if Evidence Supporting Supplementation of Vitamin C is Lacking?
Numerous reasons explain why vitamin C supplements are prescribed for pressure ulcers despite the lack of evidence from rigorously controlled studies. First, many patients with pressure ulcers do not consume proper diets and many are under metabolic stress. Because the human body excretes an increased amount of vitamin C when stressed, a deficit actually may exist in many patients. Second, vitamin C is safe and relatively inexpensive. Third, at typical supplementation levels of 500 mg twice daily (below the tolerable upper limit of 2,000 mg per day set out in the DRI), adverse effects are unlikely. If any adverse effects occurred, they could be reversed simply by stopping the supplement. Fourth, vitamin C is water-soluble — any excess is excreted in the urine. Fifth, although the evidence for use in pressure ulcer patients may be lacking, vitamin C provides many other benefits, particularly in the area of immune function. Finally, many facilities have been involved in litigation involving patients with pressure ulcers and often, the expectation is that anything that might possibly be helpful is attempted, providing it does no harm. Caution should be exercised when prescribing for patients who are prone to form kidney stones and those who have iron overload.
What are the Practice Points?
1. Encourage proper meal intake daily, including foods high in vitamin C content. 2. Remember vitamin C is water-soluble and must be replenished daily. 3. Monitor for the signs of vitamin C deficiency — eg, bleeding gums, bruised skin with many pinpoint hemorrhages, or skin that has become rough, brown, and blotchy with bruises. 4. Provide supplements if vitamin C deficiency is suspected. 5. Consult with a registered dietitian (RD) for a complete nutritional assessment and recommendations. Coming next month — Vitamin D. This article was not subject to the Ostomy Wound Management peer-review process. Nancy Collins, PhD, RD, LD/N, FAPWCA, is founder and executive director of RD411.com and Wounds411.com. For the past 20 years, she has served as a consultant to healthcare institutions and as a medico-legal expert to law firms involved in healthcare litigation. Correspondence may be sent to Dr. Collins at NCtheRD@aol.com.
1. Williams SR. Nutrition and Diet Therapy, 8th ed. St Louis, MO: Mosby–Year Book, Inc;1997:197.
2. National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: recommended intakes for individuals. Available at: www.fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=3&ta.... Accessed February 13, 2009.
3. Shai A, Maibach HI. Wound Healing and Ulcers of the Skin. Heidelberg, Germany: Springer Verlag;2005:230.
4. ter Riet G, Kessels AG, Knipschild PG. Randomized clinical trial of ascorbic acid in the treatment of pressure ulcers. J Clin Epidemiol. 1995:48(12):1453–1460.