Vitamin A is a fat-soluble vitamin whose main role is to maintain normal visual function. If vitamin A is deficient, it can easily cause night blindness. Vitamin A can also maintain the health of epithelial tissue cells and promote the synthesis of immunoglobulins. Vitamin A can maintain normal bone development and promote growth and reproduction. If animals are deficient in vitamin A, significant growth arrest can occur, and vitamin A can also inhibit tumor growth. Vitamin A is a nutritional supplement. Adding vitamin A to cosmetics can prevent roughness of the skin and promote normal growth and development. Although vitamin A has the above points and more beneficial functions for the human body, it is the same as other nutrients, what goes around comes around, and excessive intake can cause headaches, nausea, diarrhea, and splenomegaly, so moderate intake of vitamin A is needed.