Dietary vitamin C intake is correlated with how well the skin produces collagen and renews itself, according to a study published in the Journal of Investigative Dermatology.

The study followed 24 healthy adults with low baseline vitamin C in New Zealand and Germany. They were instructed to eat two SunGold kiwifruit per day (providing an estimated 250 mcg of vitamin C) for eight weeks. Skin samples were collected at baseline and again after the treatment period.

Participants who significantly increased their vitamin C status showed an apparent increase in skin vitamin C concentrations, which was associated with thicker skin through greater collagen production and increased epidermal cell proliferation, a marker of outer-layer renewal.

There was a strong correlation between blood and skin concentrations of vitamin C, compared with correlations between blood and other organs, researchers noted.

“We were surprised by the tight correlation between plasma vitamin C levels and those in the skin,” said Margreet Vissers, lead author and professor from Mātai Hāora center for redox biology and medicine. “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 an improved skin function.”

SunGold kiwifruit was selected for the study because of its high vitamin C content, but the researchers expect similar benefits from other dietary sources of vitamin C. “The important thing is to keep your plasma levels optimal, which we know can be easily achieved in a healthy person with a vitamin C intake of around 250 mg per day. The body, however, does not store the vitamin, so we recommend five-plus (servings of fruit or vegetables) a day, every day, with one of those five being a high vitamin C food, as a good habit to cultivate.”