Nutraceuticals for Skin Care: A Comprehensive Review of Human Clinical Studies

Abstract

The skin is the body’s largest organ, it participates in sensitivity and offers protection against microorganisms, chemicals and ultraviolet (UV) radiation. Consequently, the skin may suffer alterations such as photo-ageing, immune dysfunction and inflammation which may significantly affect human health. Nutraceuticals represent a promising strategy for preventing, delaying, or minimising premature ageing of the skin and also to alleviate certain skin disorders. Among them, bioactive peptides and oligosaccharides, plant polyphenols, carotenoids, vitamins and polyunsaturated fatty acids are the most widely used ingredients. Supplementation with these products has shown evidence of having an effect on the signs of ageing and protection against UV radiation ageing in several human trials. In this review, the most relevant human studies on skin nutraceuticals are evaluated and the statistical resolution, biological relevance of their results, and, the trial protocols are discussed. In conclusion, quality and rigorousness of the trials must be improved to build credible scientific evidence for skin nutraceuticals and to establish a cause-effect relationship between the ingredients the beneficial effects for the skin.

Transepidermal UV radiation of scalp skin ex vivo induces hair follicle damage that is alleviated by the topical treatment with caffeine

“…Skin cytotoxicity assessed as LDH release into the medium was highly increased after high‐dose but not after low‐dose UV‐irradiation (Figure a). Instead, both UV doses significantly increased the number of sunburn epidermal keratinocytes having pyknotic nuclei (Figure b,d), but only high dose UV‐irradiation induced acantholysis (Figure d). Interestingly, the number of apoptotic keratinocytes was significantly increased only after high dose of UV‐irradiation (Figure c,e).…”

“…increased LDH‐release with increasing UVB‐doses representing necrosis, increased HM keratinocyte apoptosis, induction of catagen, increase in TGF‐ β 2 expression, and increase in mast cell degranulation. However, considering that UVB tends to be completely absorbed by the epidermis , it is plausible that it was mainly UVA irradiation that exerted these effects in our improved irradiated full thickness skin organ culture ex vivo .…”

“…Solar ultraviolet (UV) radiation encompasses three sub‐categories of rays of different wavelengths: long wave UVA (320–400 nm), medium wave UVB (280–320 nm), and short wave UVC (100–280 nm). As more than 99% of UVC is absorbed by the ozone layer, only UVA and UVB reach the earth′s surface and impact on biological and pathological processes, especially within the organism's integuments . Although UVA penetrates into the dermis, UVB is almost completely absorbed by the epidermis .…”

Nutricosmetics: A brief overview

“…Pine bark extract supplements contain mainly flavonoids (catechins and procyanidins) and phenolic acids (caffeic, ferulic, and p‐hydroxybenzoic acids) and are able to have photoprotective effect and to increase the hydration and the elasticity of the skin. Their biological effects are related to the increase of HA synthase, to the RNA expression, and to gene expression involved in collagen de novo synthesis (Pérez‐Sánchez, Barrajón‐Catalán, Herranz‐López, & Micol, ).…”

“…Citrus extract, obtained from the immature grapefruits of Citrus paradisi , contains naringenin and rosemary extract ( Rosmarinus officinalis ), is rich in phenolic compounds and diterpenes (carnosic acid), which are components of oral supplements with anti‐inflammatory, photoprotective, and antiaging effects (Figure ). Product consumption decreases the depth of wrinkles and increases the elasticity of the skin (Pérez‐Sánchez et al, ).…”