Scientists at the University of Otago, Faculty of Medicine — Christchurch Ōtautahi, have identified a direct connection between how much vitamin C people eat and how well their skin produces collagen and renews itself. The findings show that skin health responds measurably to dietary vitamin C, not just topical treatments.
Published in the Journal of Investigative Dermatology, the research found that vitamin C levels in the skin closely mirror levels in the blood (plasma). Increasing intake through vitamin C rich foods was shown to raise both blood and skin concentrations.
Eating Vitamin C Raises Skin Levels and Thickness
The study followed 24 healthy adults in Aotearoa New Zealand and Germany. Participants who raised their plasma vitamin C levels by eating two vitamin C rich SunGoldTM kiwifruit each day showed a clear increase in vitamin C within their skin. This increase was associated with thicker skin (collagen production) and greater renewal of the outer skin layer.
Lead author Professor Margreet Vissers from Mātai Hāora — Centre for Redox Biology and Medicine within the Department of Pathology and Molecular Medicine described the results as striking.
The strength of the association between skin thickness and vitamin C intake is “compelling,” she explained.
Vitamin C Moves From Blood to Skin
According to Professor Vissers, the relationship between blood vitamin C and skin vitamin C stood out compared to other organs.
“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,” she says.
The research team also found that vitamin C circulating in the bloodstream reaches every layer of the skin and supports healthier skin function.
“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.”
Why Diet Matters More Than Creams
Professor Vissers says the findings reinforce the idea that skin health begins internally, with nutrients delivered naturally through the bloodstream.
Vitamin C is essential for collagen production, which is why it is commonly added to skincare products. However, vitamin C dissolves easily in water and does not absorb well through the outer skin barrier. The study showed that skin cells are highly efficient at absorbing vitamin C from the blood, with uptake into the outer epidermal layer appearing to be a priority.
How the Study Was Conducted
The research was funded by New Zealand company Zespri International along with a University of Otago Research Grant and included two phases. The first phase examined the relationship 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 phase involved a controlled dietary intervention carried out in Christchurch and Germany. Each location included 12 healthy participants.
Eight Weeks of Dietary Change
Participants were asked to eat two Kiwi Gold kiwifruit daily for eight weeks. This provided the equivalent of 250 micrograms of vitamin C.
“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.
German participants were recruited and tested by the SGS Institute Fresenius in Hamburg, which has the technical capability to collect samples from the outer dermal skin layer (the blister “roof”). The institute evaluated skin regeneration using ultrasound measurements of skin thickness, elasticity UV protection and epidermal cell renewal to assess overall skin function.
Clear Gains in Collagen and Skin Renewal
One of the most significant findings was a measurable rise in skin thickness among participants, indicating increased collagen production along with faster regeneration of epidermal cells.
“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.
Other Vitamin C Foods Likely Offer Similar Benefits
SunGold kiwifruit was selected for the study because of its consistently high vitamin C content. However, the researchers expect similar benefits from other vitamin C rich foods, especially fresh fruits and vegetables such as citrus, berries, capsicums and broccoli.
“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.
Daily Intake Is Key
Maintaining steady vitamin C levels in the blood is essential, since the body does not store the vitamin long term. Professor Vissers notes that healthy individuals can reach optimal plasma levels with about 250mg of vitamin C per day.
“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+ a day, every day, with one of those five being a high vitamin C food, as a good habit to cultivate.”
