Vitamin C from food boosts collagen levels in skin – landmark study

A breakthrough study from researchers at the University of Otago, Faculty of Medicine – Christchurch Ōtautahi, has found that collagen production and skin renewal directly respond to the amount of vitamin C we eat.

The study, published in the international Journal of Investigative Dermatology, shows that skin vitamin C levels are closely tied to levels of the vitamin in the blood (plasma) and can be boosted by increasing fruit intake.

Carried out on two dozen healthy adults in both Aotearoa New Zealand and Germany, the study shows that boosting plasma levels by consuming two vitamin C-rich SunGoldTM kiwifruit per day increases the amount of the vitamin in the skin, improving skin thickness (collagen production) and stimulating renewal and regeneration 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, says the strength of the association between skin thickness and vitamin C intake is “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.”

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 prioritised,” 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.

The German participants were recruited and tested by the SGS Institute Fresenius in Hamburg – their lab having the technical ability 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+ a day, every day, with one of those five being a high vitamin C food, as a good habit to cultivate.”

Reference:

Pullar, Juliet M. et al., Improved Human Skin Vitamin C Levels and Skin Function after Dietary Intake of Kiwifruit: A High-Vitamin-C Food, Journal of Investigative Dermatology, DOI: 10.1016/j.jid.2025.10.587.