Prolonged lack of sun exposure may lead to vitamin D deficiency, which affects calcium absorption and may also produce low mood. The UVB rays in sunlight, when exposed to the surface of the skin, promote the synthesis of vitamin D. Vitamin D promotes the entry of calcium into the bone cells, resulting in stronger bones. It is difficult to supplement vitamin D through diet. Sun exposure is an effective way to supplement vitamin D at almost zero cost. If you go without sunlight for a long period of time and do not take vitamin D3 supplements, it may cause vitamin D3 deficiency, which further affects calcium absorption. In addition, sunlight can stimulate the brain to secrete serotonin, serotonin has a stabilizing effect on mood, make people happy, sunshine after serotonin secretion will make people feel happy. If you don’t sunbathe for a long time, serotonin secretion decreases, which may lead to low mood. There is a disease called seasonal affective disorder, usually occurs in Europe at high latitudes, the reason is that the local winter sunshine time is short, spring sunshine time is extended that is relieved. Sun exposure may result in tanning and sunburn, but long-term sunlessness can do more harm than good, so you can choose the right sun protection measures and then plan your time for proper sun exposure.