While eating mostly raw and whole foods, I've noticed I tan more easily. (Or maybe my golden tan-orama owes thanks to my Lifestyle of Leisure and Vancouver's unusually sunny summer.) At any rate, I found this study from 2002 and thought I'd share it. The take-away message is... I'm not going to tell you! Read the damn study, you ADHD generation.
But first, some background on
carotenoids (carotenoids are fat-soluble substances, and as such require the presence of dietary fat for proper absorption through the digestive tract.):
What do carotenoids do?
Carotenoids, the colorful plant pigments some of which the body can turn into vitamin A, are powerful antioxidants that can help prevent some forms of cancer and heart disease, and act to enhance your immune response to infections. In human beings, carotenoids can serve several important functions. The most widely studied and well-understood nutritional role for carotenoids is their provitamin A activity. Deficiency of vitamin A is a major cause of premature death in developing nations, particularly among children. Vitamin A, which has many vital systemic functions in humans, can be produced within the body from certain carotenoids, notably beta-carotene (Britton et al. 1995). Dietary beta-carotene is obtained from a number of fruits and vegetables, such as carrots, spinach, peaches, apricots, and sweet potatoes (Mangels et al. 1993). Other provitamin A carotenoids include alpha-carotene (found in carrots, pumpkin, and red and yellow peppers) and cryptoxanthin (from oranges, tangerines, peaches, nectarines, and papayas).
Carotenoids also play an important potential role in human health by acting as biological antioxidants, protecting cells and tissues from the damaging effects of free radicals and singlet oxygen. Lycopene, the hydrocarbon carotenoid that gives tomatoes their red color, is particularly effective at quenching the destructive potential of singlet oxygen (Di Mascio et al. 1989). Lutein and zeaxanthin, xanthophylls found in corn and in leafy greens such as kale and spinach, are believed to function as protective antioxidants in the macular region of the human retina (Snodderly 1995). Astaxanthin, a xanthophyll found in salmon, shrimp, and other seafoods, is another naturally occurring xanthophyll with potent antioxidant properties (Di Mascio et al. 1991). Other health benefits of carotenoids that may be related to their antioxidative potential include enhancement of immune system function (Bendich 1989), protection from sunburn (Matthews-Roth, 1990), and inhibition of the development of certain types of cancers (Nishino 1998).
Here are selections from the study, found online @
Dietary Carotenoids Contribute to Normal Human Skin Color and UV Photosensitivity:
Although these studies indicate that much of the variation in tristimulus L*a*b* values is under the influence of hemoglobin and melanin in the skin, there is also considerable evidence to suggest that a third class of pigments, carotenoids, which are ingested through the diet, also have a significant influence on human skin color. Carotenoids such as ß-carotene, lycopene and lutein are highly colored (yellow-red), fat-soluble antioxidants that are found in a wide variety of fruit and vegetables. Consumed as part of the human diet, they enter the blood stream and are distributed to various organs throughout the body, including the skin, where they have been detected in all layers including the dermis, epidermis and stratum corneum (11 –16 ). A high dietary intake of carotenoids (usually in supplement form) has been shown to significantly increase the skin’s endogenous level of UV photoprotection by reducing its sensitivity to UV-induced erythema (17 –20 ). An often observed side effect in these kinds of dietary intervention studies is a noticeable yellowing of the skin (also known as carotenodermia), which is caused by the accumulation of carotenoid pigments in the skin (17 –19 ,21 ). However, although it is clear that ingestion of very large quantities of carotenoids (particularly ß-carotene) can alter skin color in the short term, much less is known about the effect of normal levels of dietary carotenoids on human pigmentation and UV photosensitivity.
The aim of the current study was therefore to determine whether carotenoids play a significant role in regulating skin pigmentation and UV photosensitivity in an unsupplemented human population, and further, to investigate whether tristumulus (L*a*b*) color measurements can be used to accurately and noninvasively predict carotenoid status and UV photosensitivity in human skin.
Reactive oxygen species are induced in the skin by solar UVA and UVB radiation and have long been suspected of contributing to the deleterious effects of cutaneous photodamage (32 ,33 ). Species such as singlet oxygen and superoxide, as well as hydroxyl and peroxyl radicals are believed to promote lipid peroxidation, protein oxidation and cross-linking, enzyme inactivation and DNA damage (32 ,33 ). In addition, it has been suggested that singlet oxygen mediates UVA-induced upregulation of interstitial collagenase in the skin, through induction of the inflammatory cytokines interleukin (IL)-1 and IL-6 (34 ,35 ). These properties of reactive oxygen species can result in compromised cell viability and biological function as well as increased degradation of the dermal extracellular matrix, all of which may mediate the appearance of two key phenotypes associated with cutaneous photodamage, i.e., photocarcinogenesis and photoageing (36 ,37 ).
Dietary carotenoids such as ß-carotene, lycopene, zeaxanthin and lutein have potent antioxidant functionality and are among the most effective naturally occurring scavengers of singlet oxygen and peroxyl radicals (24 –28 ). Reflection spectrophotometry has previously been used to detect the rise in skin levels of such carotenoids after elevated dietary intake of carotenoid supplements or carotenoid rich foods (14 ,15 ,19 ,20 ). This effect is preceded by 2 wk with a significant increase in the serum levels of these antioxidants (12 ,14 ,15 ,19 ,20 ). In the current study, we used the same spectrophotometric methods to quantify the levels of carotenoids in the skin of unsupplemented Caucasian men and women and compared these values with objective measurements of skin color and UV photosensitivity. Our findings suggest that there is a significant relationship between normal, unsupplemented levels of dietary carotenoids in the dermis and epidermis of Caucasian skin and endogenous UV photosensitivity as determined by MED (see Fig. 2 ). This supports the view that carotenoid antioxidants from a normal, unsupplemented diet accumulate in the skin and confer a measurable photoprotective benefit that is directly linked to their concentration in the tissue. Our data also suggests that the yellow component of human skin color, which is quantified by the tristimulus b* value, is closely associated with carotenoid levels in the skin of the back, forehead, inner forearm and palm of the hand (see Fig. 3 ). These observations are linked by a third finding, which suggests a selective and positive association between skin MED measurements and b* values. These data suggest that in Caucasian skin, carotenoids (and by implication, other skin antioxidant defenses, both endogenous and exogenous) may play an important role in mediating UV-photoprotection.
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In recent years, a number of studies have suggested a close association between diets rich in carotenoids, and a reduced incidence of cancer, cardiovascular disease and macular degeneration in the human population (38 –41 ). As well as being informative about the skin’s antioxidant status, dietary intervention studies have suggested that skin carotenoid concentrations are also quite closely associated with circulating serum carotenoids (12 ,14 ,19 ). Therefore it is possible that simple measurements of carotenoid concentrations in skin could also be informative about long-term circulating levels of carotenoids and thereby overall carotenoid status in the body. It is then conceivable that simple skin color or spectrophotometric measurements could be used in conjunction with dietary carotenoid intake data in prospective epidemiologic studies to determine the effect of tissue carotenoid status on the risk of developing cancer and cardiovascular disease.
