Dietary Supplements and the Skin: Focus on Photoprotection and Antioxidant Activity—A Review
by Thalita Marcílio Cândido Nutrients 2022, 14(6), 1248;
Skin health is not only significantly affected by ageing, but also by other lifestyle-related factors, such as sun exposure, exercise and eating habits, smoking or alcohol intake. It is known that the cutaneous tissue can exhibit visible signs of senescence, in the form of, for example, dull complexion, loss of firmness, or changes in pigmentation. Consumers attempt to improve skin health and appearance not only by cosmetic products, but also with the consumption of food supplements. Recently, there has been an increase in the amount of food supplements with claims that are related to skin and hair health. Nevertheless, the literature is still scarce in evidence of the efficacy of this type of products. Considering this scenario, we aim in this review to assemble studies and methodologies that are directed at the substantiation of the cutaneous health claims of food supplements. For example, we reviewed those that were indicative of antioxidant properties, improvement in pigmentation disorders, increased hydration or protection against the damages caused by ultraviolet radiation.
Astaxanthin is a ketocarotenoid, 3,30-dihydroxy-b,b-carotene-4,40-dione, which was first isolated from lobsters by Kuhn and Sorensen in 1938 [58]. This red pigment is synthesized by plant, microorganisms and algae, and has several commercial applications, such as in food, nutraceuticals, pharmaceuticals, cosmetics and aquaculture industries. In aquaculture, for example, astaxanthin is used as a feed supplement to provide color to the salmon flesh [59]. Studies have demonstrated that astaxanthin performs many essential biological functions in marine species, such as providing pigmentation, protection against UV light damage and oxidation of macromolecules, and increase stress tolerance. Another important feature of astaxanthin is its antioxidant property, which is considered higher than that of β-carotene, zeaxanthin and lutein. Astaxanthin’s strong antioxidant capacity is attributed to the presence of keto and hydroxyl groups on its terminal ionone rings [60,61,62], as observed in Figure 2.
McNulty et al. [63] compared the activity of polar and apolar carotenoids (astaxanthin, β-carotene, lutein, lycopene and zeaxanthin) on the lipid peroxidation of membranes containing cholesterol. The results indicated a correlation between changes on the membrane structure caused by the addition of carotenoids and the extent of the lipid peroxidation. All carotenoids disturbed the membrane structure except astaxanthin, and these changes were attributed to the orientation and location of the carotenoids within the membrane. Furthermore, an increase in lipid peroxidation was noticed with the addition of β-carotene, lutein, lycopene and zeaxanthin, while astaxanthin led to its reduction. The researchers pointed out that the study was carried out with a membrane system less complex than biological membranes, but the findings still provide insights on the role of carotenoids on membrane lipid peroxidation.
Similarly, in a specialized review, Pashkow et al. [64] discussed the antioxidant property of astaxanthin in modulating oxidative stress. It was suggested in the study that a specific orientation of astaxanthin molecule in the cellular membranes allows its interactions with reactive species, which help to prevent membrane lipid peroxidation.
Another important feature of astaxanthin that has been extensively investigated is its cosmetic benefit to the skin. Tominaga et al. [65] evaluated the effect of astaxanthin administration to the skin of female and male volunteers. The female group received oral supplementation and topical treatment, while the male group only oral supplementation. Both groups showed wrinkle reduction and elasticity improvement after treatment. Additionally, the parameters age spot, skin texture and moisture content were assessed in the female group. A reduction in the age spot, an improvement in the skin texture and no significant difference in the moisture content were observed. Similar to the female group, the male group did not show any difference in the moisture content, but showed a significant improvement in the transepidermal water loss after treatment.
The same research group carried out in vitro and in vivo studies to determine the effects of astaxanthin administration on skin deterioration. Regarding the in vitro studies, the suppression of inflammatory cytokine secretion in keratinocytes and matrix metalloproteinase production by fibroblasts in samples treated with astaxanthin prior UVB irradiation was observed. Further studies, with volunteers, indicated a deterioration in the wrinkle’s parameters and moisture content in the placebo group; however, no significant changes were observed in the groups treated with a 6 mg and 12 mg dosage of astaxanthin. The level of inflammatory cytokine, IL-1α, increased in the placebo and low dosage groups, but not in the high dosage group. Moreover, an improvement in skin elasticity was observed only in the group treated with 12 mg of astaxanthin [58].
Another study on the effects of astaxanthin supplementation to the skin was developed by Chalyk et al. [3]. In the study, a group of middle-aged volunteers received astaxanthin supplementation, and their skin was examined before and after treatment. Changes on the components of the skin surface were evaluated, more specifically, changes on the morphology of the surface lipids, corneocyte desquamation and microbial presence. Additionally, the plasma level of malondialdehyde, a biomarker of the oxidative stress, was assessed to evaluate the antioxidant effect of astaxanthin. Regarding the surface lipids of the skin, their droplet size and crystal structure were evaluated. A slightly increase in droplet size was observed, whereas no clear changes on the crystal structure could be detected. Changes on the skin surface were indicated by a decrease in corneocyte desquamation and microbial presence. During astaxanthin supplementation, a steadily decrease in malondialdehyde concentration in the plasma was observed.
