Vitamin C consumed through the diet is delivered directly into the skin, where it increases collagen production, accelerates skin renewal and leads to measurably healthier skin, according to new research from the University of Otago.
Published in the Journal of Investigative Dermatology, the study provides some of the clearest evidence to date that skin health responds directly to dietary vitamin C intake, rather than topical application alone.
Researchers from the University of Otago’s Faculty of Medicine in Christchurch Ōtautahi found that vitamin C levels in the skin closely mirror those in the bloodstream.
When plasma vitamin C levels increased, skin concentrations rose in parallel, supporting collagen synthesis and epidermal regeneration.
The research involved 24 healthy adults in Aotearoa, New Zealand and Germany.
Participants were asked to consume two SunGold kiwifruit per day — providing around 250 mg of vitamin C — for eight weeks.
Those who increased their vitamin C intake showed significantly higher vitamin C levels in their skin, alongside measurable improvements in skin thickness and renewal.
Lead author Professor Margreet Vissers, from the Mātai Hāora Centre for Redox Biology and Medicine, said the association between vitamin C intake and skin structure was particularly striking.
"We were surprised by how closely skin vitamin C levels tracked with blood levels — this relationship was much stronger than what we have observed in other organs."
Using ultrasound and functional testing, researchers observed increased skin thickness (an indicator of enhanced collagen production), as well as faster regeneration of epidermal cells.
Vitamin C was shown to penetrate all layers of the skin via the bloodstream, supporting overall skin function.
The findings challenge the reliance on topical vitamin C products, which often struggle to penetrate the skin barrier effectively.
While vitamin C is widely used in cosmetic formulations, it is water-soluble and poorly absorbed through the outer skin layer.
In contrast, skin cells efficiently take up vitamin C delivered internally via circulation.
Although SunGold kiwifruit was used due to its consistent vitamin C content, researchers believe similar benefits would be achieved through other vitamin C-rich foods, including citrus fruits, berries, capsicum and broccoli.
The study also highlights the importance of regular intake.
As the body does not store vitamin C long term, maintaining optimal plasma levels (~250 mg per day) is key to sustaining skin benefits.
For nutraceutical brands, the findings strengthen the scientific case for ingestible beauty products and functional foods targeting skin health, reinforcing the growing “beauty from within” market trend.