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).