Skin Protection by Carotenoid Pigments

**Background:** Solar radiation, particularly ultraviolet (UV) radiation, causes skin photodamage including burns, photoaging, immunosuppression, and skin cancers (basal cell carcinoma, squamous cell carcinoma, melanoma). Carotenoids, natural pigments found in plants and microorganisms, are promising photoprotective agents due to their antioxidant and singlet oxygen quenching properties. This narrative review summarizes the evidence for carotenoid-mediated skin photoprotection, mechanisms of action, and advances in nanoformulation delivery systems.

**Methods:** The authors conducted an open search of the PubMed database using terms (carotenoids) AND (photoprotection) AND (skin), limited to English articles from 1974–2023. From 152 initially collected articles, 89 met the search criteria, including 65 reviews and 24 clinical studies/meta-analyses/randomized trials, of which 14 met inclusion criteria. Additional articles from reference lists were added, totaling 390 references. The review was structured thematically and assessed by senior authors specializing in dermatology and plastic surgery.

**Key Results:** The review covers multiple carotenoids: - **Lycopene:** In a randomized controlled study, tomato puree (40 g/16 mg lycopene/day with olive oil for 10 weeks) reduced UVR-induced erythema by 40% compared to control (p=0.02). Lycopene supplementation also reduced mtDNA deletion (p=0.01) and MMP-1 increase (p=0.04) induced by UVR. - **β-Carotene:** A meta-analysis by Köpcke et al. (2008) showed that β-carotene supplementation provides protection against sunburn, requiring a minimum of 10 weeks; each additional month increased effect by 0.5 standard deviations. Doses ≥12 mg/day for ~10 weeks are needed. However, high doses are harmful in smokers/asbestos-exposed individuals, increasing lung cancer risk. - **Astaxanthin:** AST has strong antioxidant activity, quenching singlet oxygen several times more effectively than β-carotene, and is up to 100 times stronger than vitamin E in lipid peroxidation tests. In human skin fibroblasts, AST prevented UVA-induced changes in SOD and GSH. Oral AST (4 mg/day) reduced UV-induced skin damage and improved facial skin rejuvenation. - **Lutein/Zeaxanthin:** In a randomized, double-blind, placebo-controlled study (n=50), supplementation with 10 mg lutein and 2 mg zeaxanthin isomers improved skin brightness, elasticity, firmness, and reduced UV-induced erythema. Lutein inhibits MMP-1 and MMP-2 overexpression and stimulates TIMP-2 in vitro. - **Bacterioruberin:** A C50 xanthophyll from halophilic archaea, it shows anticancer effects in colorectal, breast, liver, and cervical cancer cell lines. Its use as a UV filter is limited by high molecular weight (500 Da) impairing skin penetration.

Carotenoids accumulate in the epidermis and dermis, with highest concentration in subcutaneous tissue. UVR reduces skin carotenoid levels by 13.5%–21.2% after blue/violet light exposure (50–100 J/cm²). The photoprotective effect is dose- and duration-dependent, with minimum 10 weeks supplementation needed for sunburn protection.

**Clinical Implications:** Carotenoids offer a natural approach to skin photoprotection, complementing topical sunscreens. They act as antioxidants, anti-inflammatory agents, and singlet oxygen quenchers, reducing oxidative stress, ECM degradation, and photocarcinogenesis. However, recommended intake doses have not been established by EFSA or the US Food and Nutrition Board. Nanoformulations (liposomes, nanoemulsions, solid lipid nanoparticles, nanostructured lipid carriers, polymer nanoparticles) improve carotenoid stability and bioavailability, enabling effective topical and oral delivery. Future research should focus on optimizing delivery systems and establishing evidence-based dietary recommendations for photoprotection.