Adults who ate two vitamin C-rich kiwifruits each day for eight weeks showed higher vitamin C levels throughout the skin, along with greater skin thickness and increased cellular renewal, according to University of Otago researchers.
By yourNEWS Media Newsroom
Regularly eating foods rich in vitamin C may strengthen the skin from within by supporting collagen formation and the replacement of aging cells, according to a study published in July 2026 in the Journal of Investigative Dermatology.
Researchers at the University of Otago in New Zealand found that vitamin C obtained through food entered the bloodstream and reached every layer of the skin. Higher vitamin C concentrations were associated with measurable changes in skin structure, including increased thickness in the deeper dermal layer and greater cellular renewal at the surface.
The findings provide evidence that dietary vitamin C does more than maintain general nutritional status. Researchers said the nutrient appears to be delivered directly to skin tissue, where it participates in biological processes involved in firmness, repair and regeneration.
Margreet Vissers, Ph.D., a University of Otago professor and the study’s lead author, said the relationship between circulating vitamin C and skin concentrations was stronger than the research team anticipated.
“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,” Vissers said.
The study followed 24 healthy adults for eight weeks. Each participant ate two kiwifruits per day, providing a consistent dietary source of vitamin C that allowed researchers to monitor changes over time.
Investigators measured participants’ vitamin C status in the blood and skin before and after the dietary intervention. They also used ultrasound imaging and skin sampling to examine changes in tissue thickness and cellular activity.
By the end of the eight weeks, vitamin C concentrations within the skin had increased. Those higher levels coincided with thicker skin, which researchers identified as an indicator of increased collagen production in the dermis.
The epidermis, the skin’s outer layer, also showed improved cellular turnover. That process replaces older or damaged cells with newer ones and contributes to the skin’s texture, resilience and protective function.
The results indicate that visible and structural aspects of skin aging may respond to nutritional changes within a relatively brief period. Researchers observed measurable differences after two months of consistent vitamin C intake rather than after a prolonged intervention lasting years.
Vitamin C is essential to collagen synthesis. It acts as a cofactor for enzymes the body uses to build and stabilize collagen, a structural protein that helps give skin its strength and firmness.
Without sufficient vitamin C, the body cannot produce or maintain collagen effectively. Declining collagen production is one of the processes associated with thinner skin, reduced elasticity and other changes that become more common with age.
The study also examined the distinction between consuming vitamin C and applying it to the skin.
Vitamin C is widely included in serums, creams and other topical products. The skin’s protective barrier, however, can limit how deeply those products penetrate, particularly when formulations are unstable or improperly absorbed.
Dietary vitamin C follows a different route. After being absorbed through the digestive system, it circulates in the blood and is delivered internally to the skin’s outer and deeper layers.
Researchers said the skin appeared particularly responsive to circulating vitamin C compared with other organs examined in earlier work. That finding suggests internal delivery may play an important role in collagen production and skin-cell renewal.
The study did not conclude that topical vitamin C has no value. Instead, it showed that obtaining sufficient vitamin C through food provides a direct pathway for the nutrient to reach skin tissue from the bloodstream.
Vissers said this internal process may be more effective at supporting deeper collagen formation than relying on topical application alone.
Kiwifruit was selected for the trial because its vitamin C content is high, consistent and relatively easy to measure. Researchers said the apparent benefits are not expected to be limited to kiwifruit.
Other dietary sources include oranges, grapefruit and other citrus fruits, as well as strawberries, blueberries and additional berries. Bell peppers, broccoli and leafy green vegetables can also contribute substantial amounts.
The research team suggested a daily intake of at least 250 milligrams of vitamin C to support optimal skin health.
Because the body does not store large amounts of vitamin C for extended periods, blood concentrations respond to recent intake. Consistent daily consumption is therefore more likely to maintain adequate levels than occasional large servings.
People who cannot obtain enough vitamin C from food may consider supplements or collagen products formulated with vitamin C. The researchers did not recommend a particular supplement, brand or commercial skin product.
Whole-food sources also provide fiber, antioxidants and other nutrients that may contribute to broader health benefits beyond skin structure.
The study was limited by its small group of 24 healthy adults and its eight-week duration. Additional research involving larger and more diverse populations will be needed to determine how age, baseline vitamin C status, diet and other factors affect the response.
The findings nevertheless demonstrate a close relationship between vitamin C circulating in the blood and the amount reaching the skin. They also show that increasing dietary intake can correspond with measurable improvements in skin thickness and cellular renewal.
The research did not evaluate cosmetic procedures or compare commercial skin-care products. Its conclusions were based on the biological changes observed after participants consistently consumed vitamin C-rich food.
The results add to evidence that skin condition is influenced not only by topical care and sun exposure but also by daily nutrition. A steady intake of vitamin C-rich fruits and vegetables may provide the raw material needed to support collagen formation, skin firmness and ongoing regeneration from within.
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