Researchers from the University of Otago and collaborators conducted a two-phase investigation. In the first phase, skin and blood samples from adults undergoing elective surgery were analysed to assess how circulating vitamin C levels relate to concentrations within different skin layers. In the second phase, 24 healthy adults took part in an eight-week dietary intervention, consuming two SunGold kiwifruit daily, providing approximately 250 mg of vitamin C per day. Skin and blood samples were collected before and after the intervention.  

The study found that increases in blood vitamin C following daily kiwifruit intake were mirrored by higher vitamin C concentrations in both the epidermis and dermis, indicating active uptake into the skin. Higher skin vitamin C levels were associated with increased skin density, a marker linked to the collagen-rich dermal matrix, and increased proliferation of epidermal cells, suggesting enhanced skin renewal.  

The authors reported a particularly strong relationship between plasma vitamin C levels and skin concentrations, highlighting the skin’s sensitivity to systemic nutrient availability. While the study did not demonstrate consistent improvements in parameters such as elasticity or UV protection, it provides direct human evidence that dietary vitamin C influences skin biology.  

The researchers note several limitations, including the small sample size and lack of a placebo control group. Nevertheless, the findings support the role of adequate dietary vitamin C in maintaining the biological processes underpinning collagen synthesis, dermal structure and epidermal turnover, reinforcing the relevance of nutrition in supporting skin health alongside clinical aesthetic and regenerative treatments.