Subjects
A total of 30 healthy subjects (female and male) were included in the study and completed it. Population characteristics are shown in Table 2. Study subjects attended the clinic at baseline (T0), and after 2 weeks (T14), 4 weeks (T28), 8 weeks (T56) and 12 weeks (T84) of product use. All subjects were included in the safety analysis data set.
Table 2 Baseline characteristics of subjects Minimal Erythema Dose (MED)
A statistically significant increase in the MED threshold compared to baseline (T0) was observed after 14, 28, 56 and 84 days of treatment (Fig. 2). The mean variation in the percentage of MED was + 1.5% at T14 (p < 0.05), + 3.0% at T28 (p < 0.01), + 6.1% at T56 (p < 0.01) and + 8.1% at T84 (p < 0.001), showing a progressive increase of the UV radiation dose necessary to induce erythema.
The Antioxidant Capacity of the Skin
Ferric Reducing Antioxidant Power (FRAP) Measurement
The mean FRAP values displayed a statistically significant increase after 14, 28, 56 and 84 days of treatment when compared to the baseline (T0) (Fig. 3). The mean variation in the percentage of the FRAP values was + 12.0% at T14, + 13.3% at T28, + 16.5% at T56 and + 22.7% at T84 (all time points, p < 0.001), indicating an increase in the antioxidant capacity of the skin.
Lipid Peroxidation (LPO) Through Malondialdehyde (MDA) Measurement
Basal lipid peroxidation (before UVA exposure) as measured by MDA concentration showed a statistically significant decrease at T28 (− 3.4%; p < 0.001), T56 (− 3.3%; p < 0.001), and T84 (− 6.4%; p < 0.001) compared to T0 (Fig. 4a).
As expected, in both measurements, 4 h and 24 h after UVA exposure (5 J/cm2), an increase in MDA was observed in all visits (T0 through to T84) compared to measurements before UVA exposure. In Fig. 4b, positive values indicate an increase in MDA concentration expressed as a percentage variation of measurements performed before UVA exposure on the same day.
Nonetheless, compared to previous visits, a smaller increase in MDA concentration was observed at each visit, both 4 h and 24 h after UVA exposure. More specifically, at T0, a 74.0% increase was observed 4 h after UVA exposure, whereas at T84 the increase was 53.3% (p < 0.001) 4 h after UVA irradiation. At 24 h post UVA exposure, a 34.7% increase was recorded at baseline (T0), whereas a 14.9% increase was registered at T84 (p < 0.001). This “reduced rate of increase” is statically significant at T28, T56 and T84 when MDA measurements were performed 4 h after UVA exposure, and at all time points (T14, T28, T56 and T84) when MDA was measured 24 h after irradiation.
Skin Moisturisation
A statistically significant increase in mean skin moisturisation values was achieved after 14 days of treatment when compared to basal conditions (T0). This increase was sustained for the whole of the duration of the study (as measured at T28, T56 and T84) (Fig. 5). Accordingly, the mean variation in the percentage of skin moisturisation compared to T0 was + 9.9% at T14, + 13.5% at T28, + 14.2% at T56 and + 13.8% at T84 (all time points, p < 0.001).
Skin Radiance
Skin gloss, also referred to as skin radiance, displayed a statistically significant increase after 14, 28, 56 and 84 days of treatment when compared to basal conditions (T0) (Fig. 6). More specifically, the mean variation in the percentage of the skin radiance compared to T0 increased by + 15.2% at T14, + 20.6% at T28, + 30.7% at T56 and + 36.1% at T84 (all time points, p < 0.001).
Skin Dark Spots (L and ITA°)
Skin lightness (L), exhibited a statistically significant increase after 14, 28, 56 and 84 days of treatment when compared to basal conditions (T0) (Fig. 7a). More specifically, the mean variation in the percentage of the L values compared to T0 increased by + 1.1% at T14, + 2% at T28, + 2.4% at T56 and + 2.6% at T84 (all time points, p < 0.001).
The mean variation in the percentage of the ITA° (Fig. 7b), measured in the brown spot, displayed an increase of 11.6% at T14, 17.2% at T28, 18.8% at T56, and 20.3% at T84, indicating a lighter skin tone (all time points, p < 0.001).
Skin Elasticity
Results showed that the overall skin firmness and elasticity improved in the course of the study (Fig. 8a–c). Skin firmness, measured as R0 (mm/s) with the Cutometer®, significantly increased after 14, 28, 56 and 84 days of treatment compared to basal conditions (T0) (Fig. 8a). The mean skin firmness (R0 = Uf), which is reduced when the skin is firmer, was − 11.2% at T14, − 13.3% at T28, − 14.4% at T56 and − 16.4% at T84 (all time points, p < 0.001).
Accordingly, both gross elasticity of the skin (Fig. 8b) (R2 parameter, Ua/Uf) and net elasticity (Fig. 8c) (R5 parameter, Ur/Ue) increased after 14, 28, 56 and 84 days of treatment compared to basal conditions (T0). The mean of gross skin elasticity increased by + 8.8% at T14, + 10.9% at T28, + 11.9% at T56 and + 13.2% at T84 (all time points, p < 0.001) and the mean of net skin elasticity increased by + 14.4% at T14, + 16.8% at T28, + 24.4% at T56 and + 28.0% at T84 (all time points, p < 0.001).
Subjective Self-Assessment of the Properties of the Product
The subjective and qualitative evaluation of the efficacy of the product showed that according to study subjects, the use of the product has been beneficial for the skin (Fig. 9: data set available in Table S1). A set of questions was answered by all subjects at all study visits (T14, T28, T56, and T84) using a self-assessment questionnaire form. The score of most of the answers (14/17) continuously improved throughout the length of the study (from T14 to T84).
Evaluation of Safety and Tolerability
The study participants reported two adverse events during the length of the study; namely, one reported that the product was difficult to digest, while the second reported slight stomach burns during the last weeks of treatment. However, based on the opinion of the investigators, these adverse events were not clearly attributable to the intake of the product. Therefore, the food supplement was considered well-tolerated.