A recent study out of St. Andrews University in Scotland found that fluctuation in fruit and vegetable consumption over a six week period was associated with skin color changes. When 35 people (ages 18-61) increased their fruit and vegetable consumption, the red and yellow hues of the skin increased due to the pigments (beta-carotene and lycopene) found in these foods. Furthermore, attractiveness was also rated higher. Conversely, as fruit and vegetable intake decreased, the skin became paler, and people were rated as less attractive. 
Studies have shown that there is an increase in vascularization of the skin in more physically fit individuals and women with higher estrogen levels, which are associated with attractiveness and fertility. Diabetes and cardiac/respiratory illnesses decrease blood oxygenation, which can leave people looking paler and leave a blue tint to the skin (not attractive). In addition to actual blood flow, carotenoids, the pigments found in yellow, orange, and red fruits and vegetables, also affect the level of reddish skin hues. In this particular study, when people increased their intake of carotenoids, the reddish hues of the skin came out and they were rated as more attractive.
Skin yellowness is related to both the carotenoids and melanin*, but in this study, participants rated people's faces that were yellow because of carotenoids, as opposed to melanin, as more attractive. The head author, Ross Whitehead said: “People who eat more fruit and vegetables have a ‘golden’ skin tone that looks healthy and attractive. Our latest research finds that even small improvements in diet produces visible benefits to skin colour. We were very surprised by how quick the changes were” (2). So, the researchers recommend you are better off eating a healthy diet as opposed to tanning if you want to look healthy and attractive.
In addition to pigmentation, fruits and vegetables offer antioxidants that can help combat free radicals in the skin. Free radicals cause aging of the skin (wrinkling) and can cause skin cancer. Smokers have high levels of free radicals from the tar in cigarettes, thus the reason a smoker’s skin tends to appear gray and wrinkles quicker than non-smokers (smokers have a higher requirement for Vitamin C- an antioxidant). Additionally, other studies show that well-balanced diets like the Mediterranean which is high in fruits, vegetables, healthy oils, nuts, seeds, and whole grains, results in healthier skin and hair.
*Melanin is a skin pigment which is dark in color and protects against UV damage, thus helping to prevent skin damage from the sun and skin cancer. However, high levels of melanin prevent Vit D formation, which is why darker individuals tend to have lower levels of circulating Vit D. Studies have shown that women with less melanin tend to be rated as more attractive, which is why many darker populations use skin lightening techniques (especially in Asia) to make the woman paler in complexion and more attractive to men.
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My recommendation: Make fruits and vegetables the foundation of your diet! Be sure to include all colors of the rainbow so that you get a wide assortment of plant pigments, nutrients, and antioxidants. Skip the tanning and opt for the sweet potatoes (in moderation of course!).
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Sources:
1. Stephen ID, Law Smith MJ, Stirrat MR, et al. Facial Skin Coloration Affects Perceived Health of Human Faces. Int J Primatol. 2009 Dec;30(6):845-57.
