CHAPTER 43
The Contribution of Dietary Nutrients and Supplements to Skin Health

Helen Knaggs, Mark Bartlett, Steve Wood, Doug Burke, and Jin Namkoong

Nu Skin and Pharmanex Global Research and Development, Provo, UT, USA

Introduction

The skin is one of the largest organs in the body and is exposed to many environmental factors affecting its appearance and health. Additionally, there are changes occurring over time in skin, determined by our genes and age. It is often said that the appearance of the skin can predict overall health or is a window to health inside of the body, so there is much interest in maintaining a healthy skin appearance and function. One approach to achieve an optimal skin appearance is through the use of topical products, such as cosmetics. However, there is now a growing body of research indicating that diet and/or oral supplementation can also influence skin appearance, as is reviewed in this chapter.

Our skin is one of our body’s largest and most complex organs. As a selectively permeable barrier, it plays a critical role in maintaining homeostasis of internal systems of the body such as moisture, temperature regulation, immune defense and even vitamin production. Several factors may impact the health and appearance of the skin including age, stress, exposure to environmental factors and nutritional status. For this reason, there is much interest and increased awareness in the connection between nutrition and skin, and perhaps even the effect that nutrition may have on the rate of skin aging. While the more obvious approach to achieving improvements in skin would be through utilizing the comprehensive array of topical products available to the modern consumer, meaningful improvements in skin health and appearance may be also obtained through changes in diet and/or the use of oral supplementation.

Historically, dietary deficiency of many of the essential nutrients (e.g. thiamine, zinc, and vitamins A and C) was first noted as a result of disruption of skin integrity or by a change in the skin’s appearance [1]. Many nutrients are important co‐factors in biochemical processes occurring within skin cells and therefore deficiencies are manifested by changes in the skin. For example, vitamin C was first discovered for its role in preventing scurvy and is an important co‐factor for collagen synthesis [2]. Another example is riboflavin, which, when deficient, causes cracks in the corner of the mouth (angular cheilitis) as well as reddening and cracking of the lips, tongue, and mouth. Zinc deficiency may be noted in poor wound healing [3], and niacin and vitamin A deficiencies can cause dry skin or, in more extreme cases, dermatitis.

Conversely, published studies seem to show that topical application of some nutrients can result in an improvement in skin condition, and this has led to the use of vitamins and other nutrients as benefit agents in cosmetic preparations. There is obvious interest in whether dietary supplementation of these nutrients can also provide benefit to skin and how this might compare with providing these same actives via the topical route. For example, higher intakes of vitamin C have been associated with a lower likelihood of a wrinkled appearance and skin dryness, independent of age, race, education, body mass index (BMI), and supplement use [4, 5], while use of vitamin C in topical products is fraught with challenges presented by the instability of the vitamin in skincare formulations. Notably, vitamin C has a number of different biologic roles in skin, including participating in collagen synthesis, skin regeneration, and wound healing [6].

Many nutrients are required by the skin for different functions, and the purpose of this chapter is to describe some of these nutrients and discuss the data describing the oral use of these for skin benefits (see Table 43.1). Below is a description of several aspects of skin health and studies of nutrients or dietary supplements that have been shown to improve skin health and appearance.

Table 43.1 Nutrients and their skin health benefits.

Nutrient groups	Specific nutrients
Antioxidants	Vitamin C	Vitamin C is necessary for collagen synthesis, and higher intakes are associated with better skin appearance [4]. Supplemental vitamins C and E for 3 months significantly reduced the sunburn reaction to UVB irradiation and skin DNA damage [7]
	Vitamin E	Vitamin E is a fat‐soluble antioxidant that accumulates in skin cells. It protects against free radical damage. However, if cell membranes are oxidized they become more rigid leading to skin wrinkle formation. Studies have shown that supplemental vitamin E reduced levels of malondialdehyde (MDA, a marker of oxidative stress) in the skin upon exposure to UV rays [8]. Skin healing is also affected by supplemental vitamin E. In 57 patients with pressure ulcers, administration of 400 mg/day oral vitamin E promoted faster healing than the placebo [9]
	Beta‐carotene	β‐Carotene can be used in the body as a source of vitamin A, which is important for skin maintenance and repair. Several studies have also demonstrated that supplemental carotenoids improve skin health
	Lycopene	Lycopene is depleted from the skin faster than β‐carotene upon UV exposure [5]. Ten weeks of supplementation with tomato paste, high in lycopene, provided protection against erythema formation following UV irradiation [10, 11]
	Lutein/zeaxanthin	Supplemental lutein/zeaxanthin has produced decreased UV damage and increased skin hydration and elasticity [12, 13]
	Astaxanthin	Subjects given astaxanthin have shown significant improvements in elasticity, moisture content, and wrinkles [14], and those consuming astaxanthin and vitamin E exhibited significant reductions in fine wrinkles and pimples, and increased moisture levels, after 4 weeks of supplementation [15]. Other studies done between 2007 and 2017 using 2–12 mg/day astaxanthin have also shown benefits that lead to a better appearance of the skin [16]
	CoQ10	An important antioxidant necessary for energy metabolism. Supplementation of 60 mg CoQ10 for 3 months significantly reduced wrinkle grade (depth and area of wrinkles) and improved skin properties [17]. In another study, supplementation with 50 or 150 mg CoQ10 for 12 weeks significantly increased skin smoothness and reduced wrinkles in 33 healthy subjects [16]
	α‐lipoic acid	A potent antioxidant that has benefit to water‐soluble and fat‐soluble portions of cells. In a preclinical study, α‐lipoic acid has been shown to reduce advanced glycation end products (AGEs) [18]
	Combinations of antioxidants	Subjects given β‐carotene, lycopene, vitamins E and C, and experienced significant protection from sun damage [19]. Consumption of lycopene, lutein, β‐carotene, α‐tocopherol, and selenium improved skin surface [20]
	Combination of antioxidants and fish oil	Subjects given 1000 mg EPA + DHA, 30 mg resveratrol, 75 mg quercetin, 140 mg purple corn cob extract (10 mg anthocyanins), 37.5 mg Rosemary leaf extract (1.5 mg carnosic acid), 200 mg citrus bioflavonoids (100 mg each naringin and hesperidin), 30 mg CoQ10, 100 mg alpha lipoic acid, 5 mg lycopene, 4 mg lutein, 1 mg astaxanthin, 50 mg D‐limonene, 1000 IU vitamin D3, and 40 mcg vitamin K2 (menaquinone‐7) had a significant reduction in skin erythema and other markers of skin damage [21]
Fish oil/omega‐3 fatty acids	Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)	Dietary consumption of fish oil is known to modulate the lipid inflammatory mediator balance and therefore is valuable in the treatment of inflammatory skin disorders. Consumption of EPA and DHA totaling 3–4 g/day for up to 3 months reduced erythema upon UV exposure in several studies [5]
Polyphenol and flavonoids	Green tea polyphenols	Polyphenols protect against free radical damage. Forty‐one women aged 25–75 years given 300 mg (green tea extract containing 97% pure polyphenols) twice daily for 2 years experienced fewer fine wrinkles and telangiectasias and overall less solar damage compared with baseline and the control group [22]
	Grape seed extract and resveratrol	When subjects received 100 mg oligomeric proanthocyanidins from grape seed extract, along with vitamin C and SiO₂ and were then exposed to UV rays, they experienced less erythema and increased skin hydration [23]
	Pycnogenol	A French maritime pine bark extract, containing 65–75% procyanidins, with potent free radical scavenging activity, increased skin hydration and improved skin elasticity [24]
	Collagen	Studies have shown that doses of 1–7 g/day can improve skin elasticity and smoothness [16]
	Ceramides (e.g. sphingomyelin)	Crucial for skin barrier integrity, 12 weeks’ administration of 1 or 2 mg/day dried chicken powder with sphingomyelin for 12 weeks significantly improved skin elasticity and feel of dry facial skin in 36 women [16]
Vitamin D		Vitamin D is a compound that is formed/activated in the skin upon sun exposure [25]. Unfortunately, there have not yet been any studies on skin health and supplementation
Minerals	Zinc	Zinc serves as a co‐factor for many important enzymes in the body. Some of the best known are important for skin healing [3, 26]
	Copper	Copper is an important co‐factor for elastin, the support structure for skin
	Selenium	Selenium is a component of the antioxidant enzyme glutathione peroxidase. Supplemental selenium and copper have shown significant protection (versus placebo) against UV‐induced cell damage [27]
Negative nutritional components	Diet high in fats and carbohydrates	Diets high in fats and carbohydrates have been shown to increase the likelihood of a wrinkled appearance [4]

Nutrients and their role in protecting against UV‐induced damage

Products designed to delay or reverse the signs of aging are in high demand, and one of the leading consumer concerns is skin aging. A major contributing factor to skin aging is UV radiation, mostly from the sun. Both UVA and UVB rays generate harmful free radicals in the skin contributing to photodamage, leading to the production of fine lines and wrinkles, as well as sunburn and skin cancers. With sun exposure and no or inadequate sun protection, the skin depends solely on its internal or endogenous defenses such as melanin for protection. Dietary micronutrients which act as antioxidants can help to protect against the free radical formation induced by UV irradiation. Some of the most widely studied nutrients that have been effective in minimizing UV damage occurring within skin include carotenoids, vitamin E (tocopherols), flavonoids, vitamin C (ascorbate), and omega−3 fatty acids (FA) [20, 28].

When given topically, vitamin A has been shown to reduce the signs of photodamage. It is most effective in its acid form, retinoic acid, and is available on prescription as Retin‐A^® (Ortho Dermatologics, USA). Since some carotenoids, such as alpha and beta carotene, can be converted to vitamin A in the body, and internal vitamin A is also essential for healthy skin function, a review of effects of oral carotenoids on the skin is of interest. In fact, there is very strong evidence to support the role of oral carotenoids in providing skin benefits, especially for UV damage.

β‐Carotene, lycopene, lutein, and zeaxanthin are major carotenoids in human blood and tissues, and are highly effective at quenching singlet molecular oxygen formed during photo‐oxidative processes. In fact, carotenoids from a normal, un‐supplemented diet accumulate in the skin [29] and confer a measurable photoprotective benefit (at least in lightly pigmented Caucasian skin) that is directly linked to tissue concentrations [30]. Dietary intake of tomato paste, which contains a number of carotenoids, including β‐carotene, lycopene, lutein, and zeaxanthin, has been shown to provide photo‐protective activity [10, 11]. Dietary supplementation with 25 mg total carotenoids a day for 12 weeks to healthy volunteers significantly diminished erythema upon UV irradiation given at week 8. This effect was enhanced when the same regimen was given with 335 mg/day (500 IU) RRR‐α‐tocopherol [31]. A 12‐week supplementation of β‐carotene from Dunaliella algae was also effective in suppressing UV‐induced erythema given at a dose of 25 mg/day to healthy volunteers [31]. It is thought that other carotenoids such as lycopene act synergistically with β‐carotene to protect the skin from UV irradiation [5]. In humans, it was shown that lycopene is depleted from the skin faster than β‐carotene upon UV exposure [32], suggesting a primary role of lycopene in mitigating oxidative damage in tissues, and an important role in the defense mechanism against adverse effects of UV irradiation on the skin. In fact, when a single UV light exposure of three times minimal erythemal dose (MED) was administered to human skin, lycopene concentrations decreased rapidly but skin β‐carotene concentrations declined slowly.

Lutein and zeaxanthin (LZ) are found in dark, leafy, green and yellow vegetables, and there is evidence that they can provide protection against UV‐induced damage. The presence of these carotenoids in the skin following dietary and oral supplementation has been demonstrated [33, 34

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