A breakthrough study by the University of Otago has found that collagen production and skin renewal are closely tied to the amount of vitamin C we eat.
Lead author and Mātai Hāora Centre for Redox Biology and Medicine researcher Prof Margreet Vissers, of Christchurch, said the strength of the association between skin thickness and vitamin C in our blood (plasma) was "compelling".
Funded by New Zealand company Zespri International along with a University of Otago research grant, the study comprised two stages.
The first established the association between blood 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’ Canterbury Cancer Society Tissue Bank.
Prof Vissers said the second stage involved a before-and-after dietary vitamin C intervention study at two sites — Christchurch and Germany — each with 12 healthy participants.
"All were instructed to consume two KiwiGold 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."
She said the German participants were recruited and tested by the SGS Institute Fresenius, in Hamburg, which had the technical ability to collect the outer dermal skin layer.
The institute measured skin sample regeneration, including ultrasound-tested measures of skin thickness, elasticity, UV protection and renewal of epidermal cells, to get 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."
Prof Vissers said SunGold kiwifruit were chosen for the trial because of their proven high vitamin C levels, but it was 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.
She said the researchers 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.
"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."
She said the study results suggested beauty really did come from within, supporting 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."
She suggested increasing dietary vitamin C intake would result in effective vitamin C uptake into all compartments of the skin.
