[BEAUTY] In a controlled human study, eating just two kiwis per day led to measurably thicker, healthier skin within weeks, highlighting how powerfully skin responds to nutrition from within.
Scientists at the University of Otago, Faculty of Medicine -Christchurch Ōtautahi, identified a direct relationship between intake of vitamin C from kiwis and the skin’s ability to produce collagen and renew itself. Published in the Journal of Investigative Dermatology, the study showed that vitamin C levels in the skin closely mirror levels in the bloodstream. Increasing vitamin C intake through food raised both plasma and skin concentrations - demonstrating that skin health responds measurably to diet, not just topical treatments.
The Study
The Study
The study followed 24 healthy adults in Aotearoa, New Zealand, and Germany. Participants who increased their vitamin C intake by eating two vitamin C–rich SunGold kiwifruit daily showed a clear rise in skin vitamin C levels. This increase was associated with greater skin thickness - an indicator of enhanced collagen production - as well as faster renewal of the outer epidermal layer. Lead author Professor Margreet Vissers of Mātai Hāora - Centre for Redox Biology and Medicine described the strength of the association between vitamin C intake and skin thickness as “compelling.”
One of the study’s most striking findings was the efficiency with which vitamin C moves from the bloodstream into the skin. According to Professor Vissers, the correlation between plasma and skin vitamin C levels was stronger than that observed in other organs. Vitamin C delivered via the blood reached all layers of the skin, supporting improved skin structure and function. This was the first time researchers demonstrated such comprehensive skin penetration from circulating vitamin C in humans.
The research consisted of two parts. In the first, plasma and skin vitamin C levels were assessed using skin tissue samples obtained from healthy patients undergoing elective surgery at Te Whatu Ora Canterbury. In the second, eight-week dietary intervention, conducted in both Christchurch and Germany, participants ate 2 Kiwi Gold kiwifruit a day (supplying ~250 mg vitamin C each). Skin biopsies and functional tests showed significant improvements in skin thickness, elasticity, UV protection, and epidermal cell renewal.
SunGold kiwifruit was used in the study because of its consistently high vitamin C content, but the researchers point out that the same effects should be achievable by eating other vitamin C–rich foods, such as citrus fruits, berries, peppers, and broccoli. Since vitamin C can’t be stored in the body for long, regular daily intake is important. The researchers estimate that 250 mg or so per day is enough to keep plasma and skin levels optimal in healthy individuals.
