You are (the colour of) what you eat
Your daily fruit and veg intake discernibly dictates the colour of your face, new research has shown.
Scientists at the University of St Andrews in Scotland began by asking 35 students to complete questionnaires logging their average daily intake of fruit and vegetables. These individuals, the data show, consumed a modestly healthy 3.41 fruit and vegetable portions per day.
Next, at three and six week time-points, the students' faces and other skin areas were imaged, the colours analysed and the results compared with the diet records.
Changes in fruit and vegetable intake during the study period, the St Andrews team found, were reflected in skin colour changes in the participants. Specifically, changes were seen in colours corresponding to the carotenoid antioxidants with which vegetables and fruits are richly endowed.
But were these changes perceptible to a person, or merely to a sensitive camera? To find out, Ross Whitehead, the lead author on the study which is published this week in the journal PLoS One, showed a second group of volunteers pairs of images prepared from four faces.
These had been manipulated to add increasing amounts of yellow colouration to the skin over a series of 22 otherwise identical images of the same face. This colour difference would have corresponded to a variation in intake of 5.55 daily portions of fruits and vegetables.
The study participants were asked to rate pairs of images of the same face as more or less healthy. Initially they were shown faces at each end of the 22-face spectrum; if they chose correctly, faces progressively nearer to one another on the colour spectrum were presented.
The subjects could discriminate a colour difference equivalent to consuming 1.89 more, or fewer, portions of fruit and veg per day.
This ties in with what has already been observed in other human studies: people rate yellower faces as more healthy and given free rein to digitally manipulate photos of faces, most people add extra yellow, mimicking the effect of extra betacarotene, the orange chemical in carrots.
The results also resonate with what goes on in the natural world. Dietary antioxidants alter animal colours and this can be used by potential partners as a measure of an individual's health and likely mating prowess. Individuals with a good diet, healthy lifestyle and antioxidants to spare can afford to spend some on making their skins look a nice colour! Humans, it seems, are no different.
So, rather than a fake tan and a nose job, the way to pull, it appears, is instead to reach for your banana and a healthy helping of nuts...