## 3 Vitamin A, Its Vitaminoids and Carotenoids' General Profile and Health Benefits
### Anti-Aging and Photo-Protective Properties of Vitamin A, Retinoids, and Carotenoids
#### 5.1.2 Photo-Protective Effect  
Early aging is directly linked with UV\({}_{\text{R}}\) exposure, as aforementioned. UV\({}_{\text{R}}\) generally consists of two categories: UV\({}_{\text{A}}\) (-320-400 nm) and UV\({}_{\text{B}}\) (-290-320 nm), where carotenoids specifically absorb in this spectrum due to their structure that is comprised of conjugated double bonds. Skin damage induced by UV\({}_{\text{R}}\), in turn, is split into two different sections: (a) acute, including cell necrosis, erythema, and inflammation, and (b) chronic, involving photo-aging with dermatological signs like wrinkles, skin spots, dryness, fine lines, and also the formation of skin cancer. UV\({}_{\text{A}}\) penetrates the deeper dermis, and its main function is to promote early aging by activating ROS, but also inducing cell apoptosis, erythema, and carcinogenesis. UV\({}_{\text{B}}\) is absorbed by keratinocytes in the epidermis and is more erythema-genic than UV\({}_{\text{A}}\), hence contributing to cancer genesis by interacting with nucleus molecules (DNA and RNA), causing mutation. Phytoene and phytofluene offer unique protection against UV radiation because of their specific absorption properties. These carotenoids are distinct from most of their counterparts that require at least seven conjugated double bonds to exhibit color and absorb light in the visible spectrum, as they possess shorter polyene chains [8; 134; 135]. Figure 10 explains the results of UV\({}_{\text{R}}\) exposure to aging and demonstrates some selected carotenoids and retinoids that have been extensively studied as a cure for these comorbidities. An alternative way of treating or preventing skin damage, except by following a diet rich in carotenoids, is by using supplements, orally or topically. Clinical trials conducted in vivo with several carotenoid supplements have revealed photo-protection against the sun's radiation. More specifically, a study on 11 men and 11 women consuming a carotenoid mixture of \(\alpha\)-/\(\beta\)-carotene and lutein, by enhancing the dose to a final 90 mg per day for 8 weeks, revealed a moderate dose-dependent increase in minimal erythema dose (MED), a decrease in lipid peroxidation, and an increase in \(\beta\)-carotene in the serum, but not in the skin. In another similar study, 20 healthy women were administered a moderate dose of \(\beta\)-carotene per day for 10 weeks and then were exposed to natural sun radiation for 13 days, without stopping this administration. Study outcomes supported that an erythema reduction was observed, along with a yellow pigmentation on the skin surface. The predominant study conclusion was that pre-treatment and treatment with carotenoids during sun exposure treatment displayed a protective effect against sunburn by raising the Langerhans cells' level and minimizing the erythema. Lastly, another similar study with  
Figure 10: Sources, bioactivity, and skin protection properties of carotenoids. two groups receiving two different supplement mixtures was tested. The first one took a mix of \(\alpha\)-/\(\beta\)-carotene, cryptoxanthin, zeaxanthin, and lutein per day, while the other group was given the same mix but with the addition of vitamin E, per day for 12 weeks. After the treatment, both teams revealed yellowish skin and higher concentrations of \(\beta\)-carotene in their serum and skin. The level of erythema was higher in those who took only the mix of carotenoids, while those who were administered the mixture with the addition of vitamin E displayed higher protection against UV\({}_{\text{R}}\), revealing the possible synergistic effects of carotenoids with other antioxidants [128]. Antioxidant and Anti-Inflammatory Profile of Vitamin A, Retinoids, and Carotenoids as Immunodefensive Mechanisms  
Carotenoids effectively neutralize harmful free radicals able to impair skin cells and contribute to premature aging.