Supplementation of which of the following micronutrients improves wound healing in patients without micronutrient deficiency?
A. Vitamin CThe vitamins most closely involved with wound healing are vitamin C and vitamin A. There is no evidence that excess vitamin C is toxic; however, there is no evidence that supertherapeutic doses of vitamin C are of any benefit. Vitamin A deficiency impairs wound healing, while supplemental vitamin A benefits wound healing in nondeficient humans and animals.
Vitamin A increases the inflammatory response in wound healing, probably by increasing the lability oflysosomal membranes. There is an increased influx of macrophages, with an increase in their activation and increased collagen synthesis. Vitamin A directly increases collagen production and epidermal growth factor receptors when it is added in vitro to cultured fibroblasts. As mentioned before, supplemental vitamin A can reverse the inhibitory effects of corticosteroids on wound healing. Vitamin A also can restore wound healing that has been impaired by diabetes, tumor formation, cyclophosphamide, and radiation. Serious injury or stress leads to increased vitamin A requirements. In the severely injured patient, supplemental doses of vitamin A have been recommended. Doses ranging from 25,000 to 100,000 IU/day have been advocated.
Zinc is the most well-known element in wound healing and has been used empirically in dermatologic conditions for centuries. To date, no study has shown improved wound healing with zinc supplementation in patients who are not zinc deficient.