@Ortho_FL Masaatsu MIYAUCHI et al. Journal of Nutritional Science and Vitaminology. 2013
The Solar Exposure Time Required for Vitamin D3 Synthesis in the Human Body Estimated by Numerical Simulation and Observation in Japan
https://t.co/tt9w2zMAiF
こちらを見ると曇りの日は10倍以上です…