In the experiment, researchers looked at 35 university students between the ages of 18 and 25, all but one of whom were white. At several points over six weeks, those students answered questions about their fruit and vegetable intake, while researchers recorded their skin-color.
According to the results, undergrads who ate more fruits and vegetables experienced an increase in skin redness and yellowness -- changes the researchers chalk up to carotenoids, or highly pigmented compounds found in many fruits and vegetables.
"Our study suggests that an increase in fruit and veg consumption of around three portions, sustained over a six-week period, is sufficient to convey perceptible improvements in the apparent healthiness and attractiveness of facial skin," said Ross Whitehead, a researcher at the University of St. Andrews' school of psychology.
Indeed, in a second arm of the same study, Whitehead and his colleagues showed 24 undergrads images of four individuals -- all white -- and asked them questions about their skin hue, as well as their perceived healthiness and attractiveness. The results were published in the journal PLoS One on Wednesday.
Dr. Carolyn Jacob, a spokesperson for the American Academy of Dermatology, expressed some skepticism about the notion that red or yellow skin tones are definitively linked with perceived attractiveness. But, she said that the connection between carotenoids and skin does exist.
"If you feed a baby too many mashed yams or carrots, they can end up getting a yellowish tint to their skin temporarily," she said."I"m a big believer in that you are what you eat," Jacob added, saying that while there is no hard and fast timeline, she would counsel patients changing their diet in order to help improve overall skin health to expect changes within two to three months.
According to the National Institute of Health's Office of Dietary Supplements, there are several hundred identified carotenoids, including provitamin A and lycopene. Red and orange fruits and vegetables, such as red bell peppers, tomatoes and mangoes are often first thought of as containing carotenoids, but others do, too.
"Carotenoids are present in a wide range of fruits and vegetables, even those that don't outwardly appear to be red or yellow," Whitehead said. "Green vegetables, for instance, are particularly high in carotenoids, but the chlorophyll in these foods masks the appearance of [them]."
(Though the recommendations vary according to age and sex, the U.S. Department of Agriculture generally recommends that women eat between 1-1/2 to 2 cups of fruit per day and between 2 and 2-1/2 cups of vegetables; men should generally eat between 2-cups of fruit and 2-1/2 to 3 cups of veggies.)
According to Whitehead and his co-authors, the new findings may have public health benefits, as they provide one more reason why people should eat enough fruits and vegetables -- one they claim is readily apparent.
"Everybody wants a pill or a short cut and I've always said that if you want to have beautiful healthy skin, you have to eat the right foods and you have to have the right lifestyle," said Dr. Doris Day, also a spokesperson for the American Academy of Dermatology and author of "Forget the Facelift."