Back tanning helps the body synthesize vitamin D and promotes calcium absorption, which is good for your health. Sunbathing on the back is a way of sunbathing on the back. Due to the large area of the back, sunbathing can effectively promote the synthesis of vitamin D in the human body and promote the precipitation and absorption of calcium. It is beneficial to human health by increasing bone density and alleviating calcium loss. Vitamin D can be supplied through food or synthesized by the skin through sun exposure. Appropriate daily outdoor sun exposure can promote the synthesis of vitamin D, each sun exposure is generally about 2 hours is sufficient. In the hot summer, it is best not to be exposed to the sun, the shade of the tree activities have the same effect of vitamin D supplementation. The back of the sun on the health of the body has a certain health effect, but need to pay attention to the back of the sun should not be too long, do a good job of sunscreen, to prevent prolonged exposure to ultraviolet rays lead to sunburn.