Vitamin C and skin health

(Source)

 From SciTechDaily

A new study led by researchers at the University of Otago, Faculty of Medicine – Christchurch (Ōtautahi), has revealed that the skin’s ability to produce collagen and renew itself is directly influenced by how much vitamin C a person consumes.

According to findings published in the Journal of Investigative Dermatology, the amount of vitamin C present in the skin closely mirrors the level circulating in the blood (plasma). The researchers also found that these levels can rise through greater fruit consumption.

The investigation involved two dozen healthy adults from Aotearoa, (New Zealand) and Germany. Participants who ate two vitamin C-rich SunGold kiwifruit each day showed an increase in plasma vitamin C, which in turn raised the vitamin’s concentration in the skin. This change supported greater skin thickness (collagen production) and encouraged renewal and regeneration in the outer layers of the skin.

Lead author Professor Margreet Vissers from Mātai Hāora (Centre for Redox Biology and Medicine, part of the Department of Pathology and Molecular Medicine), describes the connection between vitamin C intake and skin thickness as “compelling.”

“We were surprised by the tight correlation between plasma vitamin C levels and those in the skin – this was much more marked than in any other organ we have investigated,” Professor Vissers says.

“We are the first to demonstrate that vitamin C in the blood circulation penetrates all layers of the skin and is associated with improved skin function. I am very proud of my team and excited about what the data is telling us.”

Dietary Vitamin C More Effective Than Topical Forms

Professor Vissers says the study results suggest that beauty really does come from within, supporting your skin function from the inside-out by delivering vitamin C to the skin the way nature designed it – via the bloodstream.

“We know that vitamin C is required for collagen production. This fact has inspired the addition of vitamin C to many skin cream formulations. However, vitamin C is highly water-soluble and poorly absorbed through the outer skin barrier. Our study shows that the skin is extremely good at absorbing vitamin C from the blood circulation. Uptake into the outer epidermal skin layer also seems to be prioritized,” she says.

Funded by New Zealand company Zespri International, along with a University of Otago Research Grant, the study comprised two stages. The first stage established the association between plasma and skin vitamin C levels, using healthy skin tissue from patients undergoing elective surgical procedures at Te Whatu Ora Canterbury (with support from the Otago campus’s He Taonga Tapu – Canterbury Cancer Society Tissue Bank).

The second stage involved a before-and-after, dietary vitamin C intervention study at two sites (in Christchurch and Germany), each with 12 healthy participants.

“All were instructed to consume two Kiwi Gold kiwifruit daily – the equivalent of 250 micrograms of vitamin C – for eight weeks. We then collected skin samples before and after the intervention, with separate analyses allowing us to look at the skin basal layers in Christchurch and the outer dermal skin layer and skin function tests in Germany,” Professor Vissers explains.

Advanced Skin Testing Confirms Structural Improvements

The German participants were recruited and tested by the SGS Institute Fresenius in Hamburg, which had the technical capability to collect the outer dermal skin layer (the blister “roof”). The Institute measured skin sample regeneration – including ultrasound-tested measures of skin thickness, elasticity UV protection, and renewal of epidermal cells – giving a complete picture of skin function.

“The other really substantial finding showed a significant increase in the participants’ skin thickness levels, reflecting collagen production and an upsurge in the regeneration of their epidermal cells, in other words, skin renewal,” Professor Vissers says.

She says SunGoldTM kiwifruit was chosen for the trial due to its proven high vitamin C levels, but it’s anticipated that other foods rich in vitamin C, particularly fresh fruit and vegetables such as citrus, berry fruit, capsicums, and broccoli, would have similar beneficial effects.

“We suggest that increasing your dietary vitamin C intake will result in effective vitamin C uptake into all compartments of the skin,” Professor Vissers says.

“The important thing is to keep your plasma levels optimal, which we know can be easily achieved in a healthy person with a vitamin C intake of around 250mg per day. The body however, does not store the vitamin, so we recommend 5+ [of fruit] a day, every day, with one of those five being a high vitamin C food, as a good habit to cultivate.”

Reference: “Improved Human Skin Vitamin C Levels and Skin Function after Dietary Intake of Kiwifruit: A High-Vitamin-C Food” by Juliet M. Pullar, Stephanie M. Bozonet, Dörte Segger, Astrid von Seebach, Emma Vlasiuk, Helen R. Morrin, John F. Pearson, Jeremy Simcock and Margreet C.M. Vissers, 29 October 2025, Journal of Investigative Dermatology.
DOI: 10.1016/j.jid.2025.10.587

They do not discuss whether vitamin C supplementation is as beneficial.  The disadvantages of natural vitamin C is that fruit quickly loses its vitamins if it isn't fresh.  However, frozen fruit or vegetables are usually snap-frozen immediately after picking so will contain more vitamin C.