Editing Vitamin C (section)

=== Skin aging research===
There is also ongoing research on topical application of vitamin C to prevent signs of skin aging. Human skin physiologically contains small amounts of vitamin C, which supports collagen synthesis, decreases collagen degradation, and assists in antioxidant protection against UV-induced photo-aging, including [[photocarcinogenesis]]. This knowledge is often used as a rationale for the marketing of vitamin C as a topical "serum" ingredient to prevent or treat facial skin aging, [[melasma]] (dark pigmented spots), and wrinkles; however, these claims are unsubstantiated and are not supported by research conducted so far; the supposed efficacy of topical treatment as opposed to oral intake is poorly understood.<ref name="Pullar2017">{{cite journal |vauthors=Pullar JM, Carr AC, Vissers MC |title=The roles of vitamin C in skin health |journal=Nutrients |volume=9 |issue=8 |date=August 2017 |page=866 |pmid=28805671 |pmc=5579659 |doi=10.3390/nu9080866 |url= | doi-access = free | title-link = doi }}</ref><ref name="Niaimi2017">{{cite journal |vauthors=Al-Niaimi F, Chiang NY |title=Topical vitamin C and the skin: Mechanisms of action and clinical applications |journal=J Clin Aesthet Dermatol |volume=10 |issue=7 |pages=14–17 |date=July 2017 |pmid=29104718 |pmc=5605218 |doi= |url=}}</ref> The purported mechanism on supposed benefit of topical vitamin C application to slow skin aging is that vitamin C functions as an antioxidant, neutralizing [[Free-radical theory of aging|free radicals]] from sunlight exposure, air pollutants or normal metabolic processes.<ref name="Harvard2021">{{cite web |url=https://www.health.harvard.edu/blog/why-is-topical-vitamin-c-important-for-skin-health-202111102635 |title=Why is topical vitamin C important for skin health? |vauthors=Nathan N, Patel P |date=10 November 2021 |website=Harvard Health Publishing, Harvard Medical School |access-date=October 14, 2022 |archive-date=October 14, 2022 |archive-url=https://web.archive.org/web/20221014100454/https://www.health.harvard.edu/blog/why-is-topical-vitamin-c-important-for-skin-health-202111102635 |url-status=live }}</ref>  The clinical trial literature is characterized as insufficient to support health claims; one reason being put forward was that "All the studies used vitamin C in combination with other ingredients or therapeutic mechanisms, thereby complicating any specific conclusions regarding the efficacy of vitamin C."<ref name="Sanabria2023">{{cite journal |vauthors=Sanabria B, Berger LE, Mohd H, Benoit L, Truong TM, Michniak-Kohn BB, Rao BK |title=Clinical efficacy of topical vitamin C on the appearance of wrinkles: A systematic literature review |journal=Journal of Drugs in Dermatology |volume=22 |issue=9 |pages=898–904 |date=September 2023 |pmid=37683066 |doi=10.36849/JDD.7332 |doi-broken-date=November 1, 2024 |doi-access=free |url=https://jddonline.com/articles/clinical-efficacy-of-topical-vitamin-c-on-the-appearance-of-wrinkles-a-systematic-literature-review-S1545961623P0898X/ |access-date=February 25, 2024 |archive-date=February 25, 2024 |archive-url=https://web.archive.org/web/20240225202726/https://jddonline.com/articles/clinical-efficacy-of-topical-vitamin-c-on-the-appearance-of-wrinkles-a-systematic-literature-review-S1545961623P0898X/ |url-status=live }}</ref><ref name="Correia2023">{{cite journal |vauthors=Correia G, Magina S |title=Efficacy of topical vitamin C in melasma and photoaging: A systematic review |journal=J Cosmet Dermatol |volume=22 |issue=7 |pages=1938–45 |date=July 2023 |pmid=37128827 |doi=10.1111/jocd.15748 |s2cid=258439047 |url=| doi-access = free | title-link = doi }}</ref>

==== Pneumonia ====
Further research is needed to determine if prophylactic vitamin C treatment is helpful for preventing or treating pneumonia.<ref>{{cite journal |vauthors=Padhani ZA, Moazzam Z, Ashraf A, Bilal H, Salam RA, Das JK, Bhutta ZA |date=18 Nov 2021 |title=Vitamin C supplementation for prevention and treatment of pneumonia |journal=The Cochrane Database of Systematic Reviews |volume= 2021|issue= 11|pages= CD013134|doi=10.1002/14651858.CD013134.pub3 |pmc=8599445 |pmid=34791642}}</ref>