#Yellow tinge to skin skin#
Our study explores the relationship between other aspects of health and carotenoid-based skin color. Reduced blood plasma carotenoid levels have been linked to a variety of disease states including HIV infection ( Friis et al., 2001), malaria ( Das et al., 1996), risk of some cancers ( Leoncini et al., 2015 Huang et al., 2016), and myocardial infarction ( Street et al., 1994) however, objective measures of health in terms of immune function, sperm status, and oxidative stress in normal adults have not been found to relate consistently to skin carotenoids ( Foo et al., 2017a, b Phalane et al., 2017). Skin carotenoid levels therefore reflect a good diet-rich in fruit and vegetables ( Stephen et al., 2011 Whitehead et al., 2012)-but carotenoids could also act as a more general cue to human health. Once ingested, blood-borne carotenoids are secreted onto the skin where they impart a yellow-orange hue ( Edwards and Duntley, 1939 Stamatas et al., 2004 Coetzee and Perrett, 2014) which is perceived as healthy and attractive ( Stephen et al., 2011 Lefevre and Perrett, 2015). Hence, humans like other animal species obtain carotenoids through their diet. Carotenoids occur naturally in plants but cannot be synthesized by animals. In male greenfinches ( Carduelis chloris), the size of the carotenoid plumage area is correlated with the ability to resist viral infection ( Lindström and Lundström, 2000).Ĭarotenoids may play a role in human health and interpersonal attraction. For example, an increased parasite load decreases the brightness of orange spots in male guppies ( Houde and Torio, 1992) and red coloration of male sticklebacks ( Gasterosteus aculeatus) ( Milinski and Bakker, 1990). Evidence from a variety of species supports the idea of health signaling. Carotenoid ornaments are thought to be sexually selected because they represent an honest signal of health ( von Schantz et al., 1999). Such ornaments are sexually selected for example, in guppies ( Poecilia reticulata) females preferentially mate with the most brightly colored males ( Kodric-Brown, 1985), and in house finches ( Carpodacus mexicanas) males with naturally or artificially brighter carotenoid plumage are more likely to mate ( Hill, 1991). In many species of birds and fish, yellow-red carotenoid pigments are prevalent as ornamentation in beaks, feathers, skin, and scales ( Goodwin, 1986). Such findings have repercussions for public health because improved attractiveness can provide an incentive for a healthier lifestyle, including exercise and weight regulation. Hence, our results suggest that increasing cardiovascular fitness and decreasing fat levels produce a healthier skin color. Simulations of the skin color associated with higher fitness were found to appear healthier. Change in self-reported stress and sleep were further predictors of skin yellowness indicating a more general relation between health and skin tone. In a longitudinal design over 8 weeks, we found that increase in fitness and decrease in body fat were independently associated with an increase in skin yellowness.
In a cross-sectional design, we find that both higher aerobic fitness and lower body fat are predictors of skin yellowness, independent of each other and dietary fruit and vegetable intake.
Here we investigate the relationship between skin color (measured spectrophotometrically), aerobic fitness (measured by estimating the maximum volume of oxygen that a person can use per unit of time, VO 2 max), and body fat. Fitness could also raise skin carotenoids by lowering body fat (a source of oxidative stress). Exercise increases endogenous antioxidant capacity and consequently may decrease expenditure of carotenoids. Therefore, any health factor affecting oxidative balance could alter the quantity of carotenoids available to color skin. Carotenoids, as antioxidants, help maintain oxidative balance but are expended in this role. Increasing carotenoid pigmentation and skin yellowness is associated with increased fruit and vegetable intake, but whether other aspects of human health benefit skin color is unknown. In humans too, carotenoids could provide a perceptible cue to health as they impart an attractive yellow-orange color to skin.
School of Psychology and Neuroscience, Faculty of Science, University of St Andrews, St Andrews, United KingdomĬolorful carotenoid ornaments are sexually selected signals of health in many species.
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