With summer arriving in the northern hemisphere, the eternal questions of “how much sun” and “to suncreen or not to suncreen” are back in season. Through recent population studies, the pendulum seems to be swinging back in the direction of more sun is better. We know that vitamin D is important, and that the best way to get it is through exposing our skin to sunlight. Indeed, it seems like the case for sun wins hands down. Not only does that seem to be the case from the medical realm, but it’s become ingrained in our very notions of beauty. Or has it?
Skin Color and Beauty
Tanning seems like an obvious case for the social constructivists to prove, once and for all, that our conceptions of beauty are products of immersive socialization. We hear the arguments about pasty skin being attractive in times when the bourgeoisie lounged indoors counting money and adjusting powdered wigs while the proletariat labored in the fields. The story goes that having a tan was a dead giveaway that one was a low-status individual. Of course, we’ll momentarily ignore that this narrative tends to leave out the part that darker skin also carries varying racist overtones. In any case, the social constructivist points to modern society in which very few people know farmers, let alone have ever labored on a farm.
Since the cultural milieu has shifted away from an agrarian dominated context, the stigma of sun-induced dark skin has lifted. With the swing in culture, the attractiveness pendulum has swung the other way as well. This is evidenced by the widespread obsession for the “healthy glow” gained from spending time in the sun. The narrative has subsumed this observation and explained that, in fact, tans are now a signal of bourgeois status because, clearly, proletarian office drones don’t have expendable leisure time to spend laying around on the beach. Doesn’t the story fit together so nice and commonsensically!?
The Color Theory of Tanning
Design nerds, get out of CMYK, RGB, or HSV mode for a second. Scientists working with human visual perception use the (aptly named) Lab color space to most accurately replicate the way our eyes process inputs. For non-uber design geeks, Lab represents a 3-axis color system represented by L, a, and b. The L-axis describes the spectrum from Lightness-darkness. The a-axis describes the spectrum from red-green. The b-axis describes the spectrum from yellow-blue. I’ll try to just use “red-green”, et cetera when possible, but the shorthand is woven into all of the charts and quotes from the papers.
Sun tanning primarily changes values along two axes, the L (lightness) and b (yelowness). The increased melanin resulting from tanning results in a decrease in lightness and an increase in yellowness (Stamatas, et al. 2004). Therefore, we can make the simple prediction that if people indeed prefer tans resulting from the sun, we should see a preference for relatively darker skin and relatively yellower skin.
Though tanning has now been popular in Western culture for decades (Melia & Bulman. 1995), studies haven’t isolated the color variables necessary to test the “tan is beautiful” hypothesis until now. Ian Stephen, PhD and colleagues presented research in the journal Evolution and Human Behavior that address this question. Their study involved a group of white UK-based students who rated white faces, and a group of black South African students who rated black faces. The data from both groups was similar, and both are shown below…
South African rater’s adjustments of black face and similar results of Scottish rater’s of white face
The picture on the left is an example of the extremes available in the adjustment along both axes for the black faces. Note that the UK raters were rating a different face (not shown here).
Both cohorts show a strong grouping to the same quadrant. However, the quadrant selected was not what we’d expect if the “tan is beautiful” hypothesis was true. We should expect to see both groupings shifted to the top-left quadrant. It turned out that yellowness was perceived as a positive indicator of health, but relative lightness was preferred over darkness. Based on these data, we must conclude that the “tan is beautiful” hypothesis is incorrect.
The social constructivist narrative is also refuted by these findings. Since tanning behaviors are heavily influenced by socialization, we would expect to see a preference in the data for darker relative skin tones. Further, a constructivist explanation seeking to simultaneously explain pro-darker skin tanning in white individuals AND pro-lighter skin attitudes in black individuals would require the data to show the South African data to be in a different quadrant than the UK data. These data refute the existence of a culturally imparted ideal of beauty or health that can be plotted on the spectrum from lightness-darkness.
Since the “tan is beautiful” hypothesis and social constructivist arguments both fail, what explanations are we left with?
The Pasty Veg*ns Are Sexier than Sun-Bathed Carnivores Hypothesis
Enter the carotenoid. Sun exposure isn’t the only thing that affects skin color. Significant consumption of [carotenoid-containing] plant matter also impacts coloration. Stephen, et al conducted a study (results in the same paper) measuring the relationship in fruit and vegetable intake with skin color and the change in skin color resulting from carotenoid supplementation. They found that both supplementation and fruit and vegetable intake correlated with, and increased skin yellowness as measured by spectrophotometer. Further, the measured colorations were inconsistent with coloration changes from melanin (sun tan) and hemoglobin. The carotenoid coloration data fit with the results above; namely, an increase in yellowness without an decrease in lightness. This lead to another study (also reported in the same paper).
This time, rather than isolate the axes for lightness and yellowness, they provided raters with the ability to optimize for health along one axis corresponding to melanin coloration and another corresponding to carotenoid coloration. The results…
Scottish raters’ adjustments of Caucasian face. Melanin on the vertical axis. Carotenoid on the horizontal.
In a post about the same study on his blog Primal Wisdom, Don Maetz provides a heading “Carotenoid Complexion and Sun Tan Not Mutually Exclusive”. While that is literally true, it is also possible that the perception of health signaled by carotenoids and sun tans are mutually exclusive. In fact, that is what the cumulative data in Stephen, et al seems to indicate.
As the preceding image shows, when given the option to specifically optimize the appearance of health for melanin and/or carotenoids, raters unanimously preferred higher levels of carotenoid, but were almost equally mixed in preferences for melanin coloration. This adds support to the refutation of the “tan is beautiful” hypothesis, and opens the door for the “pasty veg*ns are hot” hypothesis.
The usability of data in similar previous studies has been questioned on the grounds that giving raters the choice between two options on each axis, then asking them to choose between them, is prone to errors. Stephen, et al first narrowed the image samples to ranges that might be seen in normal populations, then allowed 13 variance points along each axis. Rather than showing all at once, raters were asked to adjust the spectrum up or down to optimize the appearance of health. When plotted across both axes, this results in 39 possible selections. This seems sufficient, but I’m not sure why they didn’t allow infinite adjustments along each axis.
Other criticisms have been made that the use of Photoshop® does not provide an image representative of real-world faces. However, it’s difficult to provide a wide range of skin tones for one individual with photographic accuracy. Surely, using different individuals with different skin tones would introduce myriad variables that would render coloration assessments useless. So while there is some validity to this line of criticism, I find it rather thin.
- I’m not sure that South Africa’s history makes it the best choice for disentangling variables concerning race-based perceptions. So while I do think the method employed limits cultural influence somewhat, I’d like to see the study done where the two countries involved weren’t formerly linked via colonization. Also, the level to which South African college students are subject to “Westernization” is difficult to know.
- Since individuals’ colorations were tested before and after carotenoid supplementation, it would have been nice to see ratings of photos of this cohort before and after. Many other variables have the potential to spoil the results, but the hard parts of that experiment were mostly done by default.
- I don’t like celery.
Tanning Obsession: Evolutionary Misfire
Based on this research, I would suggest that visually perceivable results of carotenoid consumption were a reliable signal of health, and that preference is a serious candidate for positive selection that continues to influence our perceptions of health and beauty today. It is difficult to disentangle how much of this selection pressure may have been influenced by direct benefits to health and reproduction, and how it may also be an indirect signal of resource gathering ability. The data support the former…
“Carotenoids are associated with immunocompetence anddisease resistance in humans. Supplementation beneficiallyaffects thymus gland growth in children and increases T-lymphocyte number andactivity in healthy adults. Carotenoid levels become reduced in individuals with HIV and malaria, and in individuals with elevated levels ofserum α1-antichymotrypsin.”
…but the indirect role in sexual selection is a question for another day. For now, chalking up the motivation toward sun tans as an evolutionary misfire seems reasonable. When given the option, raters prefer carotenoid pigmentation to melanin. However, when not given a choice…
“In the single-pigment transforms, all faces were increasedin carotenoid and melanin color to improve healthy appearance. No effects of face sex or participant sex, or theirinteraction were found. Participants increased melanin and carotenoid color more in faces that were initially low in b*. Initial L* and a* values had smaller effects. Participants increased carotenoid more than melanin coloration.”
This demonstrates that the yellow gained through tans somewhat outweighs the darkening that comes along with it. Thus, “yellower is better” and “lighter is better” do not appear to be equal in heuristic value and could signal other things not considered here.
My current interpretation of the health implications is that a veg*n diet is inferior to a paleo diet in important categories. At the same time, strictly carnivore interpretations and/or meat & potatoes interpretations of the paleo diet seem to be inferior to veg*n diets with respect to healthy carotenoid levels. For me, that means taking the best of the veg*n and paleo approaches and eliminating the worst of both approaches. Sure, you paleo-leaning veg*ns out there can disagree, but the meat & plant paleo camp will have better looking bodies. Sure, you anti-plant-matter-leaning paleos out there can disagree, but the veg*n-leaning paleos will have better looking skin. So… do you want to be right, or do you want to be healthy and hot?
Sun exposure appears to be best used as a tool for optimal levels of vitamin D and secosteroids, not a shortcut to health or hotness. Don’t argue with me, take it up with the data. You should definitely get some sun, but you probably can’t use color as an indicator that you’ve reached an optimal level.
Summary (Just Do This)
- If health is your goal, eat a ton of carotenoid-dense fruits and vegetables.
- If looking healthy is your goal, eat a ton of carotenoid-dense fruits and vegetables.
- Get sun for the vitamin D and the secosteroids.
- Don’t get sun just for the color.
- Oh, you should probably subscribe so you don’t miss adding another dimension to the equation with the findings from this study: “Who is the fairest of them all? Race, attractiveness and skin color sexual dimorphism“
Glenn, E. N. (2008). Yearning for lightness: transnational circuits in the marketing and consumption of skin lighteners. Gender & Society, 22, 281–302. *also appears as a chapter in The Kaleidoscope of Gender: Prisms, Patterns, and Possibilities‘ (2010).
Melia, J., & Bulman, A. (1995). Sunburn and tanning in a British population. Journal of Public Health Medicine, 17, 223–229.
Stamatas, G. N., Zmudzka, B. Z., Kollias, N., & Beer, J. Z. (2004). Non-invasivemeasurements of skin pigmentation in situ. Pigment Cell Research, 17, 618–626.
Stephen, Ian D., Vinet Coetzee, and David I. Perrett. “Carotenoid and melanin pigment coloration affect perceived human health.” Evolution and Human Behavior 32, no. 3 (May 2011): 216-227. [full-text pdf]
Interesting, I just starting heading out and soaking up some sun. I do this somewhat for the 'healthy glow'/aesthetics (read: not to be such a pasty non-ve*gan, 'cause a pale predator just says 'vampire') but mostly because it elevates my mood, gets me out of doors into fresh air, and I've found that it also improves athletic performance (this being shown through both data and my personal experience).
That said, do you have any guidelines (or directions towards them) for how much and which vegetables would be best? I take 'carotenoids' to sound a bit like 'carotene', so would that mean sweet potatoes (a tuber, but still), carrots, and such? Or would even my cruciferous pals, the broccoli and cauliflower be helpful?
Yes, beta-carotene is one of many carotenoids. Lutein and lycopene are others that get mentioned a lot, but there are several hundred known carotenoids.
Things like carrots, sweet potatoes, spinach, kale, collard greens, guava, and pink grapefruit have relatively high levels of carotenoids. For carrots and greens, cooking significantly increases bioavalability… to the point that almost no carotenoids are absorbed if carrots are eaten raw. Also, a significant dose of fat in the meal is required.
My general procedure is to sautee some onions in a ton of coconut oil until they start to caramelize, then turn the heat down to medium-low and throw on a pile of greens with some garlic and butter, stir 'em up, then put a lid on and let the whole thing cook until the greens have wilted. Adding carrots to the mix works too, but they need to be boiled for a few minutes first since they cook so much slower. Oh, and then… throw a huge hunk of meat on the top.
Broccoli doesn't appear to be the best source in the bioavailability department, though it does improve serum levels of lutein. Bioavailability of carotenoids and tocopherols from broccoli: in vivo and in vitro assessment.
Mmm yeah a carnivore taking the sun out on a rock is hot. But a sweet potato loving carnivore taking the sun on a rock is even hotter! Even though I don't eat plants my skin color still seems in the yellow range unless I am mistaken. Maybe it's not all about beta carotenoids after all…
I eat almost zero fruit, but are you telling me you don't eat any vegetables or tubers? I mean, clearly it can be done in a healthy way, but getting the variety of organ meats necessary to balance out the muscle tissue would be a logistical nightmare in a lot of places.
Well, it's complicated. But no, I don't eat growing things for the most part, just running, swimming, and flying things. I have IgG allergies to most of the common vegetables and IgE to several others, plus I have celiac disease. (Don't worry, I'm not allergic to fermented grapes!) All that sensitivity makes it pretty tough for me to even digest the vegetables that my immune system doesn't react to. I also don't tolerate carbs well so, while I'm not actually allergic to sweet potatoes or yuca, I don't eat them often. No problems with meat though so that's what I eat. I buy grassfed organs from a company online when I can't get it local, and I freeze it. Maybe the organs lend a little color to my skin…?
Could you please share how you got your sensitivity tests done? I am thinking that this may need to be the next step for me… Thanks, Peggy – I enjoy your blog!
Chris Kresser (and maybe Chris Masterjohn and Stephen Guyenet) have indicated that at this point, it appears that IgG testing is of questionable value. Time and money are possibly better spent on the GAPS diet.
Quite possibly dubious results, yeah, since I appear to be sensitive to everything that grows! haha. Didn't really need to get the sensitivity tests to figure that out.
Anyway, Crunch Pickle, my ND ordered the test. I definitely have stronger reactions to certain things than to others so maybe it's been a bit useful for recognizing that, but I understand that allergies can change – one will clear up while another surfaces, rendering the test virtually useless. The underlying cause of a dysfunctional gut/nutritional deficiencies still needs to be addressed in order for anything to improve of course. But when your digestion gets screwed up every time you put something in it, no matter how perfectly paleo you are, eliminating sensitivities can speed healing. Undiagnosed celiac disease, over five years of antibiotics and other drugs, and a handful of morbidly stressful experiences led to extreme damage to my digestive system. Was the test worth anything in the end? I honestly don't know. I still can't eat anything but meat!
Ach, I hate going away from the 'net for a week and coming back to find good stuff that I missed. I supp. a little beta carotene, and do cooked sweet potatoes after some workouts, but I don't cook veggies. I just… can't. It's a matter of palatability. Maybe a little sauteeing, but my tongue don't know what 'bioavailable' means, it just knows that mushy vegetable matter tastes too much like food that's already been eaten and excreted by some other mammal. Guess I'll have to make do.
Also, Peggy, rest assured that we rock-tanning, weight-lifting, potato-munching predators <3 you too.
I ask myself if they have color calibrated the entire image chain in these studies? Did they used color calibrated print outs? What light source did they you, what color rendering index did it have? Or did they use color calibrated monitors? How did they match the images to the real life data?
Here on my screen (which isn’t calibrated), in the second image, the left bottom looks sick, like she isn’t getting enough oxygen. Problems like these can easily shift the result into any quadrant.
I would be careful to read anything into a study like this, if these problems have not been addressed.
A free copy of the paper is linked in the references so you don't have to take my word for it.. But yes, color calibration was thoroughly addressed. They go so far as to cite studies comparing color calibration methods in support of their choice. I'd say color calibration isn't a valid criticism of this study.
Andrew, how do you–if at all–reconcile your double recommendation of "eat a ton of carotenoid-dense fruits and vegetables." with your Sites that make me smarter recommendation of the Kurt Harris Archevore approach? Kurt seems to be against much plant consumption at all outside of garnish and for-taste purposes…
Thanks for the post!
"I do consume dark chocolate, coffee, tea and green tea in pretty decent amounts, in addition to colorful veggies like sweet potato, tomato and "Atkins vegetables" like salad greens, and limited citrus fruits." – Kurt Harris
And yes, I mentioned the f-word with no disclaimers. The editorial staff has been summarily fired for this mistake.
WARNING: Fruit may be fatal.
On a more serious note, I scale my fruit intake with activity. By activity, I don't mean 30 minutes of deadlifting, but 10 hour days on the bike and in the water. That means there are a lot of days that I don't eat any fruit.
Kurt's not so much against plant consumption as much as he is against making magical claims regarding plant and fiber consumption.
Interesing, Andrew. It seems we often hear "veg*n women are hot". The men don't seem to be the target of the same complements. Perhaps this is for the reasons you mention above: "the meat & plant paleo camp will have better looking bodies. Sure, you anti-plant-matter-leaning paleos out there can disagree, but the veg*n-leaning paleos will have better looking skin."
Veg*n women, lucky that female body shape is appealing mostly due to bone structure and (appropriate) fat levels, will reap significant benefit from having carotenoid pigmented skin and might not suffer so much (over the short term) for challenges of maintaining appropriate muscle mass. Over the long term though, the costs are high.
The men, whose (faces aside) physical appeal relies heavily on appropriate muscle mass aren't so lucky on a zinc and protein insufficient diet. Even if they do have good bone structure (v-shape, symmetry), muscle mass is likely to suffer. In addition to the low protein consumption low zinc levels will compound all sorts of problems.
Great post, really. Thanks so much for always taking the time to get new ideas out there.
The point you make about the differential attractiveness between men and women in this context is great. So great that I'm considering adding a couple paragraphs to the post, deleting your comment, then taking full credit for it. 🙂
Good enough to steal, eh? I'm flattered. 😀
Anyway, I couldn't help but think of this: http://www.ted.com/talks/matt_ridley_when_ideas_h…
And Part 2 is born…
Fascinating post. Thanks. 10 years ago when I got married – I had my make-up done professionally and the woman doing it says she advises all women to buy foundation a shade yellower than their skin, because it always makes them look better.
And with respect to carotenoids and skin colour, many years ago a friend worked as a sales rep for a company specialising in spirulina. He took so much himself – his palms were orange. However, he was one of the healthiest looking men I'd ever met at that time, now I know why. (He also had a great physique)
Great post, coming from Ireland the land of Freckles, and skin with the ability to burn in 0 to 60 seconds, a healthy glow with or without Makeup / Sunburn fake or real will always shine through.
I eat tons of carrots and vegetables, zero fruit, lots of fat and have never burned in my life.
I'm a triathlete, and am in the sun about 10 times what most people are, yet I never wear sunscreen either. I think a big mistake is not getting outside enough early in the spring, and then people are thrown into summer looking like Casper the ghost.
As for attractiveness. I think females can definitely be attractive without a tan, but attractive females are usually more so if tanned. This is a highly individualized metric, but for me-tan rocks:)
I also think that people with a higher fat diet tend to do better in the sun, but I have no research to back that up-just my personal experience.
Researchers in the Face Perception Group took photographs of 34 Caucasian and 41 black African men’s faces in carefully controlled conditions and measured the skin colour
of the faces. The team found that in both the African and Caucasian
populations the attractiveness ratings given by the women was closely
related to the amount of “golden” colour in the skin. Their findings
have been published in the journal Evolution and Human Behaviour.
Much attractiveness research has focused on face
shape. The role of masculinity (which for adults is thought to be a
relatively stable shape cue to developmental testosterone levels) in
male facial attractiveness has been examined, with mixed results. Recent
work on the perception of skin color (a more variable cue to current
health status) indicates that increased skin redness, yellowness, and
lightness enhance apparent health. It has been suggested that stable
cues such as masculinity may be less important to attractiveness
judgments than short-term, more variable health cues. We examined
associations between male facial attractiveness, masculinity, and skin
color in African and Caucasian populations. Masculinity was not found to
be associated with attractiveness in either ethnic group. However, skin
color was found to be an important predictor of attractiveness
judgments, particularly for own-ethnicity faces. Our results suggest
that more plastic health cues, such as skin color, are more important
than developmental cues such as masculinity. Further, unfamiliarity with
natural skin color variation in other ethnic groups may limit
observers’ ability to utilize these color cues.
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