The Facts about Vitamin C and Wound Healing
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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
• 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?
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.