Scientists at the University of Otago (New Zealand), 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.
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 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.
According to 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 said.
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,” Vissers noted
Vissers said that 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.
The research 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.
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,” Vissers explained. “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.”
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.
Maintaining steady vitamin C levels in the blood is essential, since the body does not store the vitamin long term. Professor Vissers noted that healthy individuals can reach optimal plasma levels with about 250 mg of vitamin C per day.
For more information, visit www.otago.ac.nz.
