The UK's Telegraph has the scoop:
According to Ian Stephen, an experimental psychologist at Bristol University, the secret to the perfect skin tone is found in naturally occuring chemicals called carotenoids. These are a group of some 600 organic pigments found in many plants. Stephen examined the role of beta-carotene in green and orange fruit and vegetables in changing skin tone.
He asked volunteers to compare 'before and after' photographs of Caucasian people who had been asked to start a five-a-day diet.image via photographix.ca/flickr
Stephen explained that in humans there were two pigments which had a major affect on the yellowness of fair skin: melanin and carotenoids.
The former is associated with UV exposure, the latter with certain fruits and vegetables.
He told The Sunday Times: "We found people always preferred the golden effect from diet to the darker effect from the sun."