Skin aging
Our skin consists of two main layers: the dermis and epidermis.
The dermis is the inner layer of skin that contains nerve fibers, fat cells, blood vessels, sweat and oil glands, and hair follicles.
The dermis also contains collagen and elastin, two proteins that are responsible for the structure and elasticity of the skin itself.
These proteins are subject to the process of aging. The sweat and oil glands in the dermis protect the outer layer of skin with a thin coating of oil and perspiration.
Scientists now believe that the free radical theory of disease also applies to the aging of the skin.
Free radicals are unstable small molecules generated by an oxygen environment which require stabilization by the body's antioxidant system. Free radicals occur throughout every cell in our body simply by virtue of the fact that oxygen is our principal metabolic fuel.
Strong sunlight readily generates free radicals in the skin. Our hands, face, neck, and arms are the areas usually chronically exposed to light. These parts of the body, particularly the face, are where aging of the skin shows up.
The skin protein collagen is particularly susceptible to free radical damage, and when this damage occurs, it causes the collagen protein molecules to break down and then link back up again in a different way; this is known as cross-linking. Collagen cross-linking causes the normally mobile collagen to become stiff and less mobile.
Science clearly substantiates the role that free radicals play in causing skin aging and the fact that topically applied antioxidants confer significant protection and can even partially reverse some aspects of skin aging. Indeed, various animal and human studies have proven that low molecular weight antioxidants, especially vitamins C and E, as well as alpha-lipoic acid exert protective effects against free radical damage (oxidative stress).
How vitamin C protects the skin
Research conducted at the University of Leicester in England, reported this year in the journal Free Radical Biology and Medicine, contributes to the understanding of the mechanisms involved in vitamin C's ability to help heal and protect the skin. The vitamin is an essential cofactor for the synthesis of collagen, the predominant protein in skin and other connective tissue.
Tiago Duarte, Marcus S. Cooke and G. Don Jones previously reported the discovery of the upregulation of DNA repair in vitamin C supplement users. The current research examined gene expression and DNA damage and repair in cultured human skin cells known as dermal fibroblasts (which play a major role in wound healing) that were exposed to derivative of vitamin C.
"The exposure to solar ultraviolet radiation increases in summer, often resulting in a higher incidence of skin lesions," noted Dr Duarte, who is presently affiliated with the Institute for Molecular and Cellular Biology in Portugal. "Ultraviolet radiation is also a genotoxic agent responsible for skin cancer, through the formation of free radicals and DNA damage."
In addition to vitamin C's well known ability to scavenge damaging free radicals, Dr Duarte's team uncovered additional mechanisms for the vitamin in repairing the skin and protecting it from further damage. "Our study analyzed the effect of sustained exposure to a vitamin C derivative, ascorbic acid 2-phosphate, in human dermal fibroblasts,” he explained. “We investigated which genes are activated by vitamin C in these cells, which are responsible for skin regeneration. The results demonstrated that vitamin C may improve wound healing by stimulating quiescent fibroblasts to divide and by promoting their migration into the wounded area. Vitamin C could also protect the skin by increasing the capacity of fibroblasts to repair potentially mutagenic DNA lesions."
"Even though vitamin C was discovered over 70 years ago as the agent that prevents scurvy, its properties are still under much debate in the scientific community," Dr Duarte added. "In fact, the annual meeting of the International Society for Free Radical Biology and Medicine, which will be held this year in San Francisco, will feature a session dedicated to vitamin C, entitled 'New discoveries for an old vitamin'".
"The study indicates a mechanism by which vitamin C could contribute to the maintenance of a healthy skin by promoting wound healing and by protecting cellular DNA against damage caused by oxidation," concluded Dr Cooke, of the University of Leicester's Department of Cancer Studies and Molecular Medicine. "These findings of are particular importance to our photobiology interests, and we will certainly be looking into this further".
