Do you know someone who goes to a tanning salon to get that perfectly sun-kissed skin? How about someone who religiously puts on bleaching cream to have a lighter complexion? It seems that people are not content with their skin color. Those who have more melanin want less of it, and those who have less, want more of it! It cannot be denied that this trend is a public health concern. Tanning and bleaching are not without risks. Skin cancer is a real and serious threat for those exposing themselves to tanning salons. For those undergoing certain bleaching procedures, rebound hyperpigmentation can be a disfiguring consequence. Many bleaching creams have also been found to contain toxic substances such as mercury, or adulterated with steroids. Despite these risks, people do them anyway, all in the pursuit of “beauty.”
Lighter vs. Darker? No, It’s the Glow
The target for these tanning or bleaching procedures is melanin, the brown pigment that determines our predominant skin color. Recently, scientists have been paying more attention to another pigment called carotenoids (the yellow pigment) and their role in determining how we are perceived as healthy and attractive by other humans. Several studies on carotenoids are suggesting that in our pursuit of “beauty”, we might be chasing after the wrong pigment after all! It is not about being lighter or darker complexion that makes one attractive in other people’s perception. Rather it’s the yellow healthy glow.
Carotenoids are yellow-red or orange pigments found in fruits and vegetables, including carrots, squash and sweet potatoes. They act as antioxidants and are distributed in various organs of the body. They accumulate in the different layers of the skin. The yellowing of the skin is usually subtle although large quantities can cause a harmless condition called “carotenemia” which is characterized by prominent yellowing of the skin. In optimal amounts, however, researchers have discovered that they impart a healthy yellow color which I think is what we refer to as “glow.”
Humans have been shown to be sensitive in discriminating subtle changes in skin carotenoid (yellow) pigmentation, although we may not be consciously aware of it. In a study by Stephen et al (2011)*, the participants perceived the carotenoid (yellow pigment) in skin as healthy.
Another study by Whitehead, et al (2012a), et al determined the effect of fruit and vegetable consumption on skin color. They found that an increase in fruit and vegetable consumption perceptibly changed skin color (redness and yellowness) in as little as 6 weeks. In a follow-up experiment, 24 participants were asked to identify from among a set of images (color-calibrated based on fruit and vegetable consumption), in three separate tasks, the face that appeared “more yellow,” “healthier” or “more attractive.” A complex protocol was followed to determine discrimination thresholds for each task. A perceptible change in yellowness was associated with a dietary change of around 2 portions of fruits and vegetables while health and attractiveness were similarly associated to dietary change of around 3 portions of fruits and/ or vegetables in a day.
This perception of health related to levels of carotenoids in the body and skin is not limited to humans. Among fish and birds, an optimal level of carotenoid pigments is linked to the attractive coloring of feathers or scales, and is important in selecting a mate. Among female guppies, for example, it has been observed that females preferentially mate with males who exhibit brighter yellow or orange coloration (Whitehead, 2012b). It is believed that the carotenoids only become available for ornamentation when they have performed their role in protecting the immune system. It means that sufficient amounts of carotenoids are available for immune defense, and the extra levels are being invested for ornamentation. The intensity of the yellow color is thus an indication of health. A dull color is an indication of illness.
In humans, carotenoids keep our eyes healthy. They primarily provide antioxidant protection, boost the immune system, and are important in reproductive health. Carotenoids and other antioxidants protect semen from damage. Low carotenoid levels are found among men with fertility problems, and supplementation has been shown to improve male fertility (Stephen, 2011). Apart from giving skin a healthy glow, carotenoids have been found to help prevent sun damage (Alaluf et al, 2012). So go ahead and reach for that carrot. Substitute that potato with a sweet potato. Count your daily portions of fruits and vegetables. Then be prepared to receive compliments soon!
Alaluf S,et al.(2002). Dietary Carotenoids Contribute to Normal Human Skin Color and UV Photosensitivity. J. Nutr. 132: 399–403
Stephen et al.(2011) Carotenoid and melanin pigment coloration affect perceived human health Evolution and Human Behavior 32: 216–227. In a study by Stephen et al (2011)*, a involving image manipulation for melanin and carotenoid colors taken from 51 Caucasian volunteers, different sets of Caucasian volunteers (totaling 70) were asked to make the faces look as healthy as possible by transforming the images either along the carotenoid axis, melanin axis, or both. The yellow axis was calibrated based on empirically measured carotenoid levels in another study. In the image manipulation study, participants increased carotenoid pigments more than melanin coloration. In this trial, only 68% of faces (images) were increased in melanin but all (100%) were increased in carotenoid color. Several studies across different cultures and ethnicities have found consistent results in terms of increasing yellowness on the color axis when volunteers were asked to make images appear “as healthy as possible.” (Whitehead, 2012b; Stephen, 2011)
Whitehead RD et al. (2012a). You Are What You Eat: Within-Subject Increases in Fruit and Vegetable Consumption Confer Beneficial Skin-Color Changes. PLoS ONE 7(3): e32988
Whitehead RD, Ozakinci G, Perrett DI (2012b). Attractive Skin Coloration: Harnessing Sexual Selection to Improve Diet and Health. Evolutionary Psychology,10(5): 842-854