It is often said that you are what you eat. While the phrase is not meant to be taken too literally, there is a wealth of evidence showing links between diet and health. While the effects of what someone eats on their body are complex, some relationships are well established, such as the potential for foods high in saturated fats and cholesterol to increase the likelihood of conditions such as heart disease and cancer.
On the other hand, eating more fresh fruit and vegetables has long been recommended to cut the chances of developing a range of serious illnesses. A new study in Britain seems to take this a step further. Researchers there believe that a diet rich in fruit and vegetables is not only healthier, but makes you look better too. The investigations, led by Dr Ian Stephen of the University of Bristol in England, asked more than 50 Caucasian men and women to manipulate pictures of males and females so they looked healthier.
As well as making the skin rosier and brighter - in keeping with a previous study by the same researchers that found that rosy skin was more popular - the participants also tended to show a preference for yellower skin. Dr Stephen, who carried out his research when he was a PhD student at the University of St Andrews in Scotland, believes this is related to the carotenoid pigments in fruit and vegetables.
Most carotenoids are beneficial to health as they can support the body's immune system and even reduce the likelihood of developing cancer. The body's reproductive systems can also benefit from the substances, which can be found in green leafy vegetables such as spinach, as well as carrots. So why does a person look healthier if they start showing off the carotenoids they have consumed in the skin colour of their face?
Dr Stephen believes an individual with yellower skin is signalling they are healthy because they do not have to use up all the carotenoids they consume in their immune defence. Also, it could be a case of their showing they have a diet high in carotenoids, as such a diet is likely to make that individual healthier and therefore a better choice as a mate, especially since carotenoids are linked to a good reproductive system.
So far, however, Dr Stephen admitted there was little direct scientific evidence linking a yellower skin colour with diet. "There's been stuff around the edges," he said. "It's known if you give people tablets with this stuff, it makes them yellower, but it hasn't been directly linked to fruit and vegetables." Tantalisingly, however, he said that such a link "will be very soon" confirmed by research, suggesting that a study to be published in the near future will demonstrate the link between diet and skin colour.
The findings, which indicate that lighter and yellower skin is preferred, have a message for people who enjoy sitting in the sun to get a tan, which involves making the skin darker and yellower. They suggest soaking up the rays may not be the best thing to do to make yourself look good. "People think tanning looks good and maybe it does, but perhaps it's because it looks a bit like this other change that you get from having a better diet," Dr Stephen said.
"I think you might be better off changing your diet rather than lying in the sun." The yellow tint to the skin that seems to suggest a good diet is not to be confused with the yellowness that can result from certain illnesses, as these produce a different effect. "Kidney problems do give you a yellow tint, but it makes the whites of your eyes go yellow too and it is a different shade of yellow," Dr Stephen said.
"With pigments that cause yellowness, some of them look good and some of them don't." In a statement, David Perrett, who heads the University of St Andrews' perception lab, where Dr Stephen carried out the research, said the study, published this month in the International Journal of Primatology, showed it is what we eat, and not just how much, that is crucial for looking healthy. "The only natural way in which we can make our skin lighter and more yellow is to eat a more healthy diet high in fruit and vegetables," he said.
Scientists have drawn parallels between the apparent liking for yellow tints in human faces and similar preferences in the animal world. Just as carotenoids apparently indicate healthiness in people, so are they used by birds, such as some bright yellow finches, and fish to demonstrate their good health and to attract mates. "The yellow pigment in the finches is the same pigment that we're saying may be important in human faces," Dr Stephen said. "They do get it from their diet, too, as only animals can produce these pigments."
But why should it be good for a finch to show off these carotenoid colours? The reason, Dr Stephen believes, could be that the bird is demonstrating the strength of its immune system and the fact that it is free of disease. "You take these [carotenoids] in your diet and they're used up in immune defence. If you're fighting off a lot of parasites you will be using them up," he said. Thus if an animal is healthy, it is likely to have more carotenoids left over that it can allocate as colouring for its feathers.
"It's saying: 'I'm healthy - I can find all of these carotenoids and I don't need to use them up in my immune system,'" Dr Stephen said. Dr Stephen's latest research finding, that people preferred faces with rosier cheeks, also has a rationale behind it. Healthy people, or those with higher levels of sex hormones, tend to flush more easily than smokers, old people, and those who are unfit or unhealthy. This is because in physically fit individuals, the blood tends to be more oxygenated and therefore brighter, giving them rosier skin.
The latest findings add a new twist to the already multifaceted picture of facial preferences. Earlier studies have indicated, for example, that people tend to like symmetrical faces ahead of those that are more lopsided and this too can be linked to how good a mate a person is likely to be. email@example.com