The antioxidant properties of vitamin C (ascorbic acid) and its role in collagen synthesis make vitamin C a vital molecule for skin health. Dietary and topical ascorbic acid have beneficial effects on skin cells, and some studies have shown that vitamin C may help prevent and treat ultraviolet (UV)-induced photodamage.

Contents of Skin and Vitamin C availability

Our skin naturally contains Vitamin C, it is found at high levels in both the dermis and epidermis^{1, 2}. The vitamin C content of the epidermis is higher than the dermis. Aging, however, causes a decline in vitamin C content in both the epidermis and dermis². Excessive exposures to UV light or pollution (cigarette smoke and ozone) may also lower vitamin C content, primarily in the epidermis^{3, 4, 5}.

Vitamin C in the skin is normally transported from the bloodstream. Transport proteins specific for ascorbic acid are found on cells in all layers of the skin. Oral supplementation with vitamin C effectively increases vitamin C levels in the skin^{6, 7}.

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Vitamin C Deficiency

Symptoms of vitamin C deficiency (known as Scurvy) is a condition characterised by general weakness, anaemia (lack of blood), gingivitis (gum disease), and skin haemorrhages caused by a prolonged deficiency of vitamin C (ascorbic acid) in the diet. Scurvy can be prevented by consuming as little as 10 mg of ascorbic acid daily⁸.

Functions in Healthy Skin

Photoprotection

Vitamin C limits the damage induced by ultraviolet (UV) light exposure. Vitamin C is not a “sunblock” because it does not absorb light in the UVA or UVB spectrum. Rather, the antioxidant activity of vitamin C protects against UV-induced damage caused by free radicals⁹.

UV light decreases vitamin C content of our skin, the levels of this vitamin C reduction is dependent on the intensity and duration of UV exposure¹⁰.

Multiple studies have found that oral supplementation with a combination of vitamin C and vitamin E effectively increases MED (a measure of photoprotection from UV light in skin) and decreases the occurrence of skin redness caused by hyperaemia (increased blood flow). Which occurs in any skin injury, infection, or inflammation^{11, 12}.

Photodamage/Wrinkling

The accumulation of oxidative damage to proteins is a distinguishing feature of both photodamage (photoaging) and intrinsic aging; this oxidative damage can lead to changes in skin structure. In addition to its antioxidant functions, vitamin C regulates the synthesis of the structural protein collagen. The role of vitamin C in the hydroxylation of collagen molecules has been well scientifically documented¹³. Hydroxylation of collagen is necessary for its extracellular (outside the cell) stability and support of the epidermis.

In cell culture models, vitamin C supplementation has many beneficial effects in combating photodamage. Specifically, vitamin C has been shown to stabilize collagen Messenger RNA, thus increasing collagen protein synthesis for repair of the damaged skin¹⁴. Vitamin C also increases the proliferation rate of fibroblasts, a capacity that decrease as our body’s age¹⁵. Further, vitamin C has been proven to stimulate DNA repair in cultured fibroblasts¹⁶ (a cell in connective tissue which produces collagen and other fibres).

Dry skin

Scientific studies have shown that higher intakes of dietary vitamin C decreased the risk of dry skin¹⁷, this suggests that vitamin C may have effects on the loss of water through our skin (trans-epidermal water loss (TEWL)). In cell culture models, the addition of vitamin C promotes the barrier functions of our skin, to help reduce the amount water lost through the skin.

Wound healing

One of the most compelling reasons to recommend vitamin C is for skin health and chronic wound healing. There is an association between vitamin C deficiency and the loss of important skin functions. Poor wound healing is associated with decreased collagen formation, thinning of the outermost layer of the skin and bleeding beneath the skin due to skin fragility and loss of connective tissue¹⁹.

Other functions

Environmental pollutants, such as ozone, can decrease vitamin C levels in the skin and lead to free radical damage⁴. Smoking also leads to increased wrinkling and decreased collagen synthesis, which leads to a decline in plasma vitamin C levels²⁰.

Conclusion

Vitamin C is an essential part of skin health both as a small molecular weight antioxidant and as a critical factor for collagen synthesis. Vitamin C contributes to photoprotection, decreases photodamage, and is needed for adequate wound healing. Oral supplementation with vitamin C may help prevent UV-induced damage, especially in combination with supplemental vitamin E. Dietary vitamin C may also provide photoprotection current scientific data suggest that vitamin C is most effective in protecting against damage induced by UV light and also has helps in the treatment of photodamage and/or skin wrinkling. Although vitamin C appears to benefit dry skin and may support wound healing, further research is needed to determine the effect of vitamin C on both. Lastly, the greatest effects of vitamin C supplementation are seen when it is combined with other micronutrients, such as vitamin E and zinc.

Scientific Evidence

1.       http://www.ncbi.nlm.nih.gov/pubmed/8288904

2.       https://www.ncbi.nlm.nih.gov/pubmed/11710935

3.       https://www.ncbi.nlm.nih.gov/pubmed/8440901

4.       https://www.ncbi.nlm.nih.gov/pubmed/9214574

5.       https://www.ncbi.nlm.nih.gov/pubmed/9436614

6.       http://www.ncbi.nlm.nih.gov/pubmed/12419467

7.       https://www.ncbi.nlm.nih.gov/pubmed/9870553

8.       https://www.ncbi.nlm.nih.gov/pubmed/12569111

9.       http://www.ncbi.nlm.nih.gov/pubmed/1390169

10.   http://www.ncbi.nlm.nih.gov/pubmed/8151122

11.   https://www.ncbi.nlm.nih.gov/pubmed/15675947

12.   https://www.ncbi.nlm.nih.gov/pubmed/9448204

13.   https://www.ncbi.nlm.nih.gov/pubmed/1720597

14.   http://www.ncbi.nlm.nih.gov/pubmed/3351329

15.   http://www.ncbi.nlm.nih.gov/pubmed/7518857

16.   https://www.ncbi.nlm.nih.gov/pubmed/18973801

17.   https://www.ncbi.nlm.nih.gov/pubmed/17921406

18.   http://www.ncbi.nlm.nih.gov/pubmed/9284103

19.   https://www.ncbi.nlm.nih.gov/pubmed/28805671

20.   https://www.ncbi.nlm.nih.gov/pubmed/20347467