Plant-Based Foods for Skin Health: A Narrative Review

The potential role of plant-based foods in the promotion of skin health is an emerging area of nutrition research. Plant-based foods are rich in bioactive compounds, including vitamin C, vitamin E, beta carotene, polyphenols, and phenolic acids, which can contribute to oxidant defense, lower in ﬂ ammation, and promote structural support of the skin. Epidemiological studies have associated higher intakes of select fruits and vegetables with positive skin health. Bene ﬁ cial effects of certain fruits, vegetables, nuts, legumes, and polyphenolic-rich beverages on the skin have been reported, with each of these providing a unique phytochemical composition. Although most studies use extracts, this review will focus on data from whole foods and minimally processed products. Collectively, the evidence to date suggests a promising future for plant-based dietary interventions that promote skin barrier health and function. However, addi- tional research is required to address issues such as the optimal quality and duration of intake as well as potential mechanisms. Studies in the above areas will help formulate speci ﬁ c targeted dietary recommendations. improvement in hydration, hyperpigmentation, wrinkles, erythema, collagen, and elasticity. More clinical studies are needed to determine the amount and duration of consumption for each food to elicit bene ﬁ cial effects and to understand the underlying mechanisms.

skin barrier health and function. A majority of the trials discussed used study designs of dietary components and foods individually, at times, above dietary recommendations. However, the goal of this review is to spark interest in this field, as well as provide an overview of the available data for both the public and nutrition professionals who have an interest in the role of diet for the maintenance of skin barrier health and function. This review aims to provide more specificity in terms of the fruits and vegetables that may improve skin barrier function and meet the recommendations of the 2020-2025 Dietary Guidelines for Americans (DGAs).

METHODS
Articles were identified on PubMed and Google Scholar using the following key terms (or combinations of them): "fruit," "vegetable," "nut," "legume," "bean," "food," "skin," "wrinkle," "erythema," "hydration," "elasticity," "aging," "photoaging." All studies available in English were reviewed. Eligibility criteria for clinical trials included dietary interventions and skin parameter measurements relevant to wrinkles, erythema, hydration, and elasticity. Studies focused on plant-based foods and beverages that were whole or processed into extracts were considered. Extracts were equated to equivalent quantities as whole foods or beverages to deduce feasibility of consumption. Isolated compounds were not considered. Dermatological skin diseases such as acne and psoriasis were not considered. Animal or in vitro studies were included for select plant-based foods or relevant bioactive compounds that supported potential mechanisms of action for the clinical trials.

RESULTS
Twenty studies involving 13 plant-based foods were identified, including 8 fruits and vegetables, 2 nuts and legumes, and 3 polyphenolic-rich beverages. Products used in dietary interventions included whole foods, nutritional pastes, beverages, juice, and extracts (Table). For the included trials, study participants were adults between 18 and 86 years old. Most studies reported the Fitzpatrick skin phototype (FSPT), a standard tool used to categorize an individual's skin type based on melanin pigmentation and factors and potential skin reaction to UVR exposure. Individuals with FSPT I and II have less melanin pigmentation and increased sensitivity to harmful effects of UVR such as sunburn and premature aging, and individuals with FSPT III and IV tend to tan. 16

Fruits and Vegetables
Fruits and vegetables are rich in bioactive compounds including carotenoids, 17 vitamins, and polyphenols. 18 These are distributed to the skin and promote oxidant defense and structural integrity and reduce inflammation to help protect against UVR-induced damage. 18,19 Many fruits and vegetables are excellent sources of VitC, with reduced intake of VitC associated with dry or wrinkled skin in women. 20 VitC is a cofactor for prolyl and lysyl hydroxylases that are important for collagen synthesis. It also functions as a major circulating antioxidant that can quench reactive oxygen species (ROS) derived from UVR. 21 A number of fruits and vegetables are also substantial sources of carotenoids. Supplementation of carotenoids in the range of 24 to 25 mg per day for 12 weeks in healthy men and women aged 20 to 57 was observed to significantly reduced UV-induced erythema. 22,23 In another study, carotenoid supplementation also inhibited an increase in UVR-induced CD45þ inflammatory cells. 24 In addition, the intake of 13.1 mg of carotenoids daily for 26 days significantly reduced oxidative stress-induced lymphocyte DNA damage in young adults. 25 Mangos. Mangos (Mangifera indica L) are rich in carotenoids (especially beta carotene) as well as VitC and the phenolic gallic acid. 26 Ataulfo mangos have the highest VitC content among the mango varieties commonly found in the United States, 27 with 85 g providing an estimated 107 mg of VitC (143% of the recommended dietary allowance [RDA] for adult women). 28 This mango variety is also rich in beta carotene, with 85 g providing 2219 mg (16% of the RDA for adult women). Ataulfo mangos are 4 times higher in beta carotene than the reference level reported by the US Department of Agriculture (USDA) Food Data Central (FDC) #169910 (640 mg/100 g of raw mango). 28 A significant decrease in deep facial wrinkles was seen in postmenopausal women aged 50 to 70 with FSPT II or III after consuming 85 g (0.5 cup) of fresh-frozen Ataulfo mangos 4 times a week for 16 weeks. 29 Curiously, those who consumed 250 g (1.5 cups) in the same intake pattern had an increase in wrinkles. This may have been due to the amount of sugar present in the fruit. Glucose and fructose are known to increase glycation of collagen and elastin fibers, which disrupt the integrity of the subcutaneous tissue supporting the skin. 30 Mangos are also the primary dietary source of the polyphenol mangiferin. Ataulfo mangos have been found to contain 183 to 996 mg/g of mangiferin depending on harvest date, which is higher than 4 other mango varieties tested. 27 UV-irradiated mice fed a mango extract containing 13.5% of mangiferin for 12 weeks showed a significant decrease in wrinkle length, along with an increase in collagen bundles and inhibition of collagen fiber damage through a reduction in inflammation. 31 Supplementation of mangiferin to mice also resulted in a decrease in the pro-inflammatory indices of inducible nitric oxide synthase, interleukin-1b, and interleukin-6 and inhibition of nuclear factor-kappa B subunit 2 and IkB phosphorylation in the skin. 32 Melons. Melons (Cucumis melo L) are rich in VitC and beta carotene, with cantaloupes containing higher amounts than honeydews. 33 In 44 White subjects aged 18 to 50 with FSPT II or III, consumption of dried melon pulp juice concentrate (MPJC) was associated with decreased UVR-induced damage. Participants consumed the MPJC or a color-matched control capsule daily along with a control topical cream for 30 days. 34 Participants' buttocks were irradiated at baseline and after supplementation, and a significant increase in the minimal erythema dose (MED) was observed in the MPJC group compared with controls. The MED represents the lowest amount of UVR required to produce mild sunburn or redness. A higher MED is thought to correlate with decreased susceptibility to UVR damage. 35 In another study, examining women aged 40 to 70 with FSPT II to IV, participants consumed a capsule containing the MPJC along with grape seed extract, VitC, and zinc for 8 weeks. Significant improvements in skin color, luminosity, dark circles under the eyes, erythema, and overall subjective satisfaction was noted. 36 The authors of both studies suggested that superoxide dismutase was a primary driver contributing to the observed effects of MPJC; however, this mechanism seems unlikely since superoxide dismutase is a protein that is catabolized during digestion and not absorbed intact. 37 Regrettably, the studies did not provide information to estimate the equivalent amount of melons consumed. One cup of cantaloupe melon cubes (USDA FDC #169092) provides about 58.7 mg of VitC (65%-90% of RDA for adults) and 3230 mg beta carotene. 28 Oranges. Oranges (Citrus sinensis) are widely recognized as being rich in VitC. The nutrient and polyphenolic profiles differ depending on the variety and environmental factors during the growing season. 38 The most common flavonoids found in citrus include quercetin, hesperidin, and narirutin. Another flavonoid subclass, the anthocyanins, are found in blood oranges, which give the pulp and juice its red color. Inhibition of UV-induced erythema was observed in 20 White participants aged 26 to 47 years with FSPT II and III when supplemented with 100 mg/d of a powdered extract, derived from a combination of blood orange varieties containing 2.8% to 3.2% anthocyanins, 1.8% to 2.2% hydroxycinnamic acids, 8.5% to 9.5% flavone glycosides, and 5.5% to 6.5% VitC, all on a weight-to-weight basis. 39 The same study found a significant inhibition of UV-induced melanogenesis in 25 participants with FSPT II and IV, aged 40 to 70 years. Melanogenesis was assessed in 3 areas containing solar lentigos as well as in 1 lentigo-free area on each hand. Melanin is an important essential molecule for skin photoprotection, absorbing a broad range of UV rays, dissipating energy as heat to protect the skin from DNA damage. 40 However, chronic UV exposure, particularly to UVB radiation, could exceed the melanin absorbance threshold, resulting in increased ROS generation. Increased melanogenesis can disrupt the equilibrium within melanocytes and may be observed as darkening of the skin or hyperpigmentation. 41 Blood orange juice provides about 6.65 mg of total anthocyanins per 100 mL serving (USDA flavonoid database 3.3, 2018). 42 A reduction in DNA damage and an increase in the concentrations of plasma anthocyanin cyanidin 3-glucoside, VitC, and carotenoids were noted in adults aged 20 to 27 years old who consumed 600 mL of blood orange juice for 21 days. 43 In mice, the intake of a citrus extract rich in hesperidin and narirutin for 7 weeks resulted in a significant inhibition of UV-induced transepidermal water loss (TEWL). This is an important measure of skin barrier function that assesses water diffused from the dermis and epidermis through the stratum corneum to the skin surface. 44 The study also reported improved skin hydration and reduced epidermal thickening. 45 Consumption of unripened Jeju mandarin orange extract (50, 100, and 200 mg/kg body weight) for 10 weeks in mice reduced UV-induced TEWL, wrinkle depth, epidermal thickness, and collagen degradation. 46 The amount of anthocyanins and VitC in the extract in the human study mentioned earlier 39 can be met through 300 mL or 1.3 cups of blood orange juice, containing 225 mg VitC and 10.5 mg cyanidin-3-glucoside. 43 Tomatoes. Tomatoes (Lycopersicon esculentum) are rich in lycopene, a carotenoid with strong oxidant defense capabilities. 47,48 Human skin and plasma contain the highest amounts of lycopene compared with other body tissues. 49 Among men and women aged 26 to 67 with FSPT II, a significant decrease in UV-induced erythema, along with an increase in serum lycopene levels, was observed after 10 weeks of daily intake of 40 g of tomato paste, providing approximately 16 mg lycopene, compared with an olive oil control group. 50 In women aged 21 to 74 with FSPT I or II, consumption of 55 g of tomato paste containing 16 mg of lycopene along with olive oil daily for 12 weeks significantly increased the erythemal threshold compared with the intake of olive oil alone. 51 Additionally, those consuming the tomato paste showed a significant increase in procollagen I and inhibition of collagenase metalloproteinase-1 expression, mitochondrial DNA damage, and a reduction in fibrillin-1 in response to UVR-induced tissue injury. Twelve-week supplementation with a carotenoid-rich tomato nutrient complex that included rosemary extract significantly decreased UV-induced erythema in adults aged 20 to 50 with FSPT I or II compared with a control containing medium-chain triglycerides. 52 A significant increase in serum lycopene was also observed in the tomato nutrient complex group, but not the control group. In the studies mentioned here, 40 to 55 g of tomato paste provided 16 mg of lycopene. Raw tomatoes contain less bioavailable form of lycopene compared with processed tomatoes. 53 Therefore, an estimate of 390 g or 2.5 cups of raw tomatoes (USDA FDC #321360) may be needed to provide the same level of lycopene as the studies. 28 Due to seasonal availability of local tomatoes, processed tomato products may be a suitable alternative due to consistent availability, longer shelf life, and concentration of bioavailable bioactive compounds.
Kale. Kale (Brassica oleracea) is rich in carotenoids, VitC, and glucoraphanin, a glucosinolate that is converted to sulforaphane, which can decrease inflammation and oxidative stress mediated by the Nrf2 signaling pathway. 54,55 Consumption of carotenoid-rich curly kale extract (2200 mg lutein, 1000 mg beta carotene, 50 mg alpha carotene, 400 mg lycopene, 700 mg zeaxanthin, 100 mg cryptoxanthin) daily for 10 months improved collagen I and elastin levels in 29 women aged 40 to 56 with FSPT II compared with an olive oil control. 56 In addition, a significant increase in epidermal and dermal thickness was observed when mice prone to accelerated skin aging consumed spray-dried kale or a glucoraphanin-enriched kale extract daily for 43 weeks, compared with controls. 57 The beneficial effects were prominent in the glucoraphanin-enriched group compared with those who consumed spray-dried kale. The amount of carotenoids in the extract closely matches 1 cup (118 g) of boiled kale (USDA FDC #169238), which contains about 5880 mg lutein and zeaxanthin, 2040 mg beta carotene, 11.8 mg alpha carotene, and 30.7 mg cryptoxanthin. 28 Stir-frying and steaming were reported to preserve more glucosinolates compared with boiling. 58 Pomegranates. Pomegranates (Punica granatum L) are rich in anthocyanins, the ellagitannin punicalagin, and ellagic acid. 59 A significant increase in MED was observed with daily intake of 8 oz (237 mL) of pomegranate juice or its extract for 12 weeks in 74 women aged 30 to 40 with FSPT II to IV. 60 The pomegranate juice and extract provided similar amounts of punicalagin and ellagic acid. The intake of pomegranate juice concentrate powder significantly decreased wrinkle formation, inhibited reduction in collagen type I and hyaluronan concentrations, and increased skin water content in UVBtreated mice compared with the group not receiving the powder. 61 Supplementation also inhibited pro-inflammatory cytokine interleukin-1b and myeloperoxidase activity that promotes the formation of ROS, while increasing the antiinflammatory cytokine interleukin-10. One cup of pomegranate juice is equivalent to a serving of fruit and counts toward the daily recommendation.
Passion Fruits. Passion fruits (Passiflora edulis) contain edible seeds that provide polyphenols that can benefit the skin. 62 The seeds have more polyphenols than the pulp or rind, with piceatannol only present in the seeds. 63 Improved skin barrier function, as evidenced by a significantly increased moisture content and decreased TEWL, was observed in 32 Japanese women aged 35 to 55 with dry skin complaints who consumed passion fruit seed extract containing 5 mg piceatannol for 8 weeks compared with controls. 64 Increased facial water content and viscoelasticity were also observed in adults who consumed piceatannol-rich beverages for 8 weeks. 65 Piceatannol, a polyphenolic compound, has been shown to increase oxidant defense, as evidenced by a reduction in amine-induced hydrogen peroxide generation in rats after 6 weeks of daily supplementation. 66 Approximately 2.3 g of raw passion fruit seeds are needed to obtain 5 mg (2.2 mg/g) piceatannol, 63 an amount that may be obtained from 1 fruit.
Grapes. Grapes (Vitis vinifera) contain significant amounts of polyphenols, including anthocyanins, 67 flavan-3-ols, resveratrol, 68 and proanthocyanidins 69 as well as VitC. 70 Six months of daily supplementation with a grape seed extract providing 162 mg of proanthocyanidins to 12 Japanese women who had melasma (brown skin patches) significantly reduced the melanin index and melasma size and improved skin lightening. 71 The same research group had previously supplemented guinea pigs with the grape seed extract for 8 weeks and observed an inhibition in melanin synthesis and increased lightening of the skin. 72 Another study observed a significant decrease in lentigos on the cheeks of women aged 30 to 60 years who consumed 200 mL of a beverage containing 200 mg of dealcoholized red wine oligomeric proanthocyanidins compared with a calorie-matched control drink for 12 weeks. 73 Stratum corneum water content was significantly increased in the test group and significantly decreased in the controls. Taken together, the studies suggest reduced melanogenesis and skin lightening from the proanthocyanidins-rich grape extracts. Improved cellular oxidant and anti-inflammatory defenses, as seen with an inhibition of Nrf2-dependent antioxidant enzymes in the skin, along with a reduction in epidermal thickness, were observed with 14 days of grape seed extract supplementation (2 mg/kg body weight) in UV-irradiated mice. 74 The previously mentioned studies provided about 3 to 4 times higher proanthocyanidins than the estimated mean daily intake of 57.7 mg in the United States. 75 Generally, grapes are a good dietary source of proanthocyanidins, and their juice contains about 524 mg/L. 75 To obtain 162 to 200 mg of proanthocyanidins provided in the studies, approximately 300 to 382 mL or 1.3 to 1.6 cups of grape juice should be consumed.
The DGAs recommend 2 cups of fruits, especially whole, and 2.5 cups of vegetables with specific suggested amounts for dark-green, red, and orange ones. 76 Although the studies mentioned illustrate that the estimated amount of select fruits and vegetables generally aligns with the guidelines, different plant foods have different phytochemical profiles, so specificity is needed when making dietary recommendations for different skin conditions.

Nuts and Legumes
Nuts and legumes have an abundance of beneficial fats and are a good source of plant-based protein as well as other micronutrients. A lower risk of severe photoaging, assessed by a physician using a 6-grade ordinal scale, has been associated with a higher intake of n-3 polyunsaturated fatty acids (n-3 PUFA) from plant-based sources 77 and monounsaturated fatty acids (MUFA) from vegetable oils but not dairy products and meats. 78 Furthermore, women with the highest intake of n-3 PUFA, especially eicosapentaenoic acid, were less prone to severe photoaging. 77 Although plant-based foods are not significant sources of eicosapentaenoic acid, it can be metabolized from alpha linolenic acid that is commonly found in vegetable and flax seeds, walnuts, and oils. The 2020-2025 DGAs recommend an intake of 5 oz per week of nuts, seeds, and soy products. 76 However, higher amounts may be required to promote specific skin health benefits.
Almonds. Almonds (Prunus dulcis) are rich in alpha tocopherol, MUFA, and polyphenols, all of which provide oxidant defense. 79,80 One ounce of almonds (USDA FDC #170567) contains 8.94 g of MUFA, 3.5 g of PUFA, 6 g of protein, and 7.27 mg of alpha tocopherol. 28 Alpha tocopherol is the most abundant form of vitamin E in human tissues and functions in part by quenching lipid peroxidation 81 and increasing the levels of plasma glutathione (GSH), an endogenous antioxidant. 82 A significant decrease in overall wrinkle severity and width was observed in postmenopausal women aged 55 to 80 with FSPT I or II who consumed almonds providing 20% of total calories for 16 weeks, compared with energy-matched nut-free snacks. 83 A follow-up study using the same dietary intervention found a significant decrease in average wrinkle severity in postmenopausal women aged 47 to 84 with FSPT I or II after 24 weeks of daily nut intake. In addition, facial pigment intensity decreased significantly with almond intake, and no changes were observed in the nut-free snack group. 84 The beneficial effects of almonds on skin esthetics are thought to be due in part to their oxidant defense capability. At 10% or 20% of total daily calories, almonds have been found to increase both plasma and red blood cell alpha tocopherol 85 and decrease pro-inflammatory high-sensitivity C-reactive protein. 86 An increase in glutathione peroxidase activity has also been noted from daily intake of 0.7 oz (20 g) of almonds for 8 weeks in overweight and obese women. 87 Additionally, the consumption of almond skin powder decreased oxidized glutathione, increased plasma glutathione and the plasma glutathione-to-oxidized glutathione ratio, and upregulated glutathione peroxidase activity in healthy adults. 88 Glutathione neutralizes free radicals and is a cosubstrate for glutathione peroxidase, an important enzyme that quenches hydrogen peroxide and lipid hydroperoxides. 89 Based on a 2000 kcal diet, 20% of calories from almonds estimates to 400 kcal, which can be obtained from approximately 2.4 oz (68 g), providing 21.5 g of MUFA (9.7% of 2000 kcal), 8.4 g of PUFA (3.8% of 2000 kcal), and 17.5 mg of alpha tocopherol (117% of RDA). However, it is likely that the amount of calories metabolized and absorbed from almonds is less than the estimated amount. A study has shown that the energy content of almonds determined primarily by Atwater factors overestimates the actual amount of metabolizable energy. 90 The only current PUFA and MUFA recommendations are from the American Heart Association, which are based on heart health outcomes and recommend a daily intake of 10% and 15%, respectively from total calories. 91 Although daily intake of 2.4 oz of almonds is higher than the current American Heart Association guidelines of 1.75 oz of nuts 4 times per week, the previously mentioned study focused on the benefits on skin. The results are of interest and should be repeated at lower intakes, possibly for longer periods of time.
Soybeans. Soybeans (Glycine max) are rich in the isoflavones genistein and daidzein that have structures similar to estrogen and may interact with this hormone's receptors. 92 The reduction in estrogen during menopause has been associated with changes in the dermal layers that increase skin conditions such as wrinkling, dryness, and poor wound healing. 93 One ounce of mature raw soybeans (USDA FDC #174270) contains 1.2 g of MUFA, 3.2 g of PUFA, and 10.3 g protein. A significant decrease in fine wrinkles and increased skin microrelief (a network of furrows and ridges) at the lateral canthi and elasticity in the cheeks was observed in Japanese women aged 35 to 48 who consumed an isoflavonerich soybean extract (40 mg soy isoflavone aglycones) for 12 weeks compared with a control. 94 Additionally, a significant increase in hydration and a decrease in stratum corneum thickness was observed in adults aged 25 to 60 who consumed a soybean and barley beverage for 8 weeks compared with controls. 95 An increase in hyaluronan levels in dermal fibroblasts and a decrease in hyaluronidase-2 (an enzyme that degrades hyaluronan) mRNA and protein levels were seen only in the soy/barley group, further supporting the improvement seen in skin hydration. The amount of 40 mg of isoflavones is similar to data from current epidemiological and clinical studies suggesting an intake of 50 to 90 mg of isoflavones or 15 to 25 g of soy protein per day for women for general health. 96

Polyphenol-Rich Beverages
Coffee, green tea, and cocoa are widely consumed beverages rich in polyphenols. These beverages typically contain the methylxanthines caffeine and theobromine, with caffeine a possible concern for some consumers. The US Food and Drug Administration has cited 400 mg of caffeine a day as an amount not typically associated with negative effects. 97 Importantly, decaffeination has little to no effect on polyphenol content, 98,99 thus it may be a suitable alternative form of coffee and tea.
Cocoa. Cocoa (Theobroma cacao) is a rich source of flavan-3ols (flavanols), a flavonoid-subclass that can inhibit lipid peroxidation, neutralize ROS, and chelate metals that enhance the production of ROS. 100 Furthermore, cocoa flavanols can inhibit enzymes involved in ROS production and upregulate protective genes involved in cellular stress responses. Cocoa is particularly rich in theobromine and is relatively lower in caffeine (w10 mg) per serving compared with tea and coffee. Among Korean women aged 43 to 86, daily consumption of a cocoa beverage containing 320 mg of flavanols for 24 weeks significantly improved measures of elasticity and the MED, as well as skin roughness, suggesting an improvement in wrinkle depth compared with a nutrientmatched control drink. 101 In addition, intake of a cocoa beverage containing 329 mg of flavanols for 12 weeks significantly decreased UV-induced erythema, skin roughness, scaling, and TEWL and increased skin density, thickness, hydration, and blood flow to the cutaneous and subcutaneous tissues in women aged 18 to 65 with FSPT II compared with a drink containing low flavanol at 27 mg. 102 The cocoa beverages used in the studies were powders mixed with water. It is important to note that most processing of natural cocoa powders reduces the amount of flavanols. 103 Therefore, depending on the source of cocoa powder, the amount needed to obtain w 300 mg of flavanol can vary substantially.
Coffee. Coffee (Coffea L) is rich in polyphenols, particularly chlorogenic acid. 104,105 An observational study assessed the amount of chlorogenic acid consumed from coffee by 131 Japanese women aged 30 to 60 and noted a significant association between higher consumption of coffee (!450 mL/d) or coffee polyphenols (!900 mg/d) with lower hyperpigmentation. 106 Daily consumption of a decaffeinated beverage containing 297 mg of coffee polyphenols for 4 weeks significantly improved scaly skin in the cheeks and around the mouth in Japanese women aged 25 to 35 compared with a control drink. 107 In another study, the daily intake for 8 weeks of a 100 mL decaffeinated beverage with 270 mg coffee polyphenols containing mainly chlorogenic acid significantly improved skin permeability barrier function, as evidenced by a decrease in dryness, TEWL, and pH, as well as an increase in stratum corneum lipids, lactic acid, and hydration, in 49 women with dry, itchy, and cracked skin compared with controls. 108 Roasted coffee beans contain 7.95 to 8.75 mg/g of total polyphenols that could decrease to 1.17 to 1.58 mg/g after 12 months of storage. 109 The Specialty Coffee Association recommends brewing coffee at a ratio of 1.63 g of beans per fluid ounce of water. 110 Considering that 29% and 36% of American adults drink 2 and 3 or more cups per day, respectively, this would equate to a daily intake of 270 to 300 mg coffee polyphenols when one uses an estimate of 8 mg total polyphenols per gram of beans. 111 Green Tea. Green tea (GT; Camellia sinensis) provides a number of flavanols, 112 particularly epigallocatechin gallate (EGCG). 113 A review of studies on tea flavanols reports protection against UVR and anti-allergenic properties that may be beneficial to the skin. 114 Daily consumption of 1 L of a GT drink providing 1402 mg total of tea flavanols (980 mg EGCG) for 12 weeks in 60 women aged 40 to 60 with FSPT II significantly decreased UV-induced erythema, roughness, TEWL, and viscoelasticity (resistance toward an applied vacuum) compared with a control beverage devoid of polyphenols. 115 Increased serum flavanol levels, skin density, and biological elasticity (ability to return to original position) were also observed. In both groups, skin volume, scaling, and hydration significantly increased, which likely reflected the large amount of fluid consumed. However, the GT group showed a greater increase in hydration compared with the controls. In another study, supplementation with GT extracts containing 540 mg total flavanols for 12 weeks significantly decreased UV-induced erythema in 14 adults with FSPT I or II when given the maximum UVR dose. 116 However, no significant changes were seen when the same adults were given lower levels of radiation. In humans, flavanol metabolites have been found in the skin after daily intake of GT extract containing 450 to 540 mg of tea flavanols for 12 weeks. 116,117 An increase in the expression of genes related to skin moisturizing factors in response to EGCG was also observed in vitro. 118 Typically, 1.8 to 3 g of leaves are used to brew a cup of tea, but the amount of EGCG varies drastically from 0.07 to 6.1 mg/3 g of leaves. 119 Therefore, depending on the quality and processing of the tea leaves, as little as 1 or more than 10 cups of green tea may be needed to achieve an intake of at least 500 mg of tea flavanols. The European Food Safety Authority has found that modest amounts of green tea infusions and similar beverages are safe, but caution against taking more than 800 mg/d EGCG through extracts, because rare cases of liver injury have been reported. 119

CONCLUSION
The studies mentioned here collectively provide evidence of the potential benefits of plant-based foods for skin health and esthetics (Figure). In an era of personalized nutrition, this review can help dietitians provide better dietary recommendations of certain plant-based foods to compliment a well-balanced diet. Many of the foods and extracts discussed are rich in bioactive compounds such as VitC, alpha tocopherol, beta carotene, polyphenols, and phenolic acids that provide oxidant defense, support mechanisms to lower inflammation, or promote structural support and UV protection in the skin. 120 Some of the clinical studies above explored the role of whole and minimally processed foods (juice, beverage, paste), and others used extracts. When possible, we equated the intake of bioactives from extracts to the amounts present in whole food and beverages to evaluate the feasibility of bioactivity from dietary intake; however, further studies are clearly warranted to confirm these speculations. The food items discussed were added to the participants' habitual diet, mostly on a daily basis, with some at higher amounts than the currently recommended daily amounts. Overall, we found that the consumption of colorful fruits and vegetables abundant in vitamins, carotenoids, anthocyanins, and polyphenols is indicated for skin health and esthetics. In general, yellow, orange, and red fruits such as mangos, melons, citrus, tomatoes, and vegetables such as red bell peppers and dark-green leafy kale are good sources of carotenoids. Fruits with deep red or purple colors such as grapes, pomegranate, and passion fruit are rich in anthocyanins and polyphenols. Nuts and legumes are also encouraged, along with cocoa, coffee, and tea that are rich in polyphenols. Decaffeinated options do not appear to dilute benefits and should be considered for caffeine-sensitive individuals. Although intake of an abundance of plant-based foods is desirable, overconsumption of a single food or extract can be of concern, as illustrated previously by the intake of a large amount of mangos. 29 In conclusion, clinical studies in the field of nutrition and skin research support growing evidence to help dietitians make targeted dietary recommendations. More investigations on whole foods and beverages, as well as those fortified with plant-based extracts, are needed to extend current findings.