That's because the yellow-red pigments found in fruits and vegetables, called carotenoids, are associated with changes in skin color, the authors found. They also found that the skin pigment changes may be viewed as healthier and more attractive.
Researchers from the University of St. Andrews in Scotland monitored the fruit and vegetable intake of 35 Caucasians over a six-week period and measured skin color changes. In a separate experiment, they investigated how attractive people found the skin color changes associated with the increased intake of fruits and vegetables.
Increasing consumption of carotenoids is associated with a more yellowish skin tone, and the authors also found that eating more fruits and vegetables correlated with skin that appeared to have a healthy red tone.
"Such coloration is held to contribute beneficially to the appearance of health in human faces as is the case with skin yellowness," the authors wrote.
The effects on skin color required only a moderately increased intake of fruits and vegetables, they said.
Carotenoids are made by plants. They are distributed through the bloodstream to various organs, including the skin. Previous studies have found that high levels of carotenoids offer protection against ultraviolet radiation by decreasing the skin's sensitivity to redness caused by UV light.
But it's the perception on attractiveness that the authors think could potentially be the key to encouraging people to eat more fruits and vegetables, something that adults in the U.S. and the U.K. don't do very much.
"Such inadequate intake is estimated to precipitate 2.6 million premature deaths per year worldwide," they wrote. "Fruit and vegetable consumption affects skin carotenoid levels; this may lead to skin color change in a fashion that is known to contribute to the appearance of health. It follows that dietary change may be motivated by illustrating to individuals these beneficial effects on appearance."
The authors also add, however, that further research is needed to determine whether carotenoids affect non-Caucasians the same way.