# Development and Effect Analysis of UVB-LED General Lighting to Support Vitamin D Synthesis
## 5 Conclusions and Future Research  
This study recommends UVB-LED general lighting for indoor dwellers to support vitamin D synthesis. To confirm the efficacy of this recommendation, rats were used for the experimental tests. UVB-LED general lighting with 500 lux and over illuminance and safe UVB light radiation levels were developed. This UVB-LED light was installed with a power converter, drive control panel, and main controller to adjust the visible ray. The UVB-LED module was controlled by a 10 W constant current type AC/DC converter where the power could be adjusted between 82 and 108 mA. Furthermore, 100 mW UVB-LED light bulbs (L company) were installed in each of the four corners of the apparatus. A quartz crystal with the ability to penetrate 99% of UVB wavelength was used as a cover. Next, the UVB-LED lighting module was equipped with UVB-LED general lighting with up to 82 mA of power. The safety of the UV light source was checked against the photobiological safety standard (IEC62471), and it was shown to be within the safest exempt level (AUV <= 0.001 W/m\({}^{2}\), NUV <= 10 W/m\({}^{2}\)). Animal testing to confirm the difference between the UVB-LED general lighting (proposed lighting) and normal lighting was performed. The rat was chosen as an appropriate test subject and a test light-proofed apparatus was prepared. The proposed lighting was investigated in the G1 (experimental) and normal lighting in the G2 (control) groups, and each group consisted of 10 rats. The illuminance of the bottom of the cage was maintained at 300 lux and was provided with a 7-day acclimatization period. The experiment was performed for 14 days after the above-mentioned step. At 23:00, 02:00, and 06:00 h, 0.5 mL of blood samples were obtained from the caudal vein on both the 7 th and 14 th days. The blood samples were then separated through centrifugation and a vitamin D analysis kit (Cayman, 501050) was used. The analysis results showed that both the G1 and G2 groups had an insignificant difference of 0.32 on the first day. However, on the seventh day, the G1 group showed 25(OH)D levels at 15.10, and was 6.8% (0.97 ng/mL) higher than that of G2. Additionally, on the fourteenth day, the G1 group showed a 25(OH)D content of 13.22, which was 7.3% (0.9 ng/mL) higher than that of the G2 group. On the basis of the comparison analysis by time interval, Days 7 and 14 both showed that the G1 group had higher 25(OH)D levels. Through the present study, it was confirmed that UVB-LED general light, which can safely provide UVB light indoors, could increase the amount of vitamin D synthesis in an animal's body.  
In the future, research on a lighting control method that provides different amounts of UV light over time for optimal lighting services will be conducted. Furthermore additional animal experiments will be carried out to confirm the effectiveness of the proposed lighting. Various analysis methods (KIT) and experimental environments will be applied in the additional animal experiments. In addition, clinical studies that keep test subjects inside for a determined amount of time in light-proofed experimental setups are required to further prove the efficacy of vitamin D synthesis. Furthermore, an investigation into light systems that closely imitate not only UVB light characteristics, but also the hourly color-temperature and wavelength of natural light is planned.  
Writing of the original draft, S.-T.O. Conceptualization and supervision, J.-H.L. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIP) (No. 2017R1A2B2005601). This work was supported by the Priority Research Centers Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2019R1A6A1A03032988).  
The authors declare no conflicts of interest.