The efficacy and role of AD preparations is mainly to prevent and treat vitamin A deficiency and vitamin D deficiency rickets. The main manifestations of vitamin A deficiency are as follows: 1. eye manifestations, signs and symptoms of the eye are the classic manifestations of vitamin A deficiency, mainly night blindness and blurred vision in dark light. 2. skin manifestations, mainly manifested as dry skin, easy to flake, itchy, dry hair and loss of luster. 3. growth and development disorders, manifested as height lagging, easy to lose tooth enamel and loss of luster in severe deficiency. 4. 4, increased susceptibility to infection, vitamin A subclinical or suspected subclinical deficiency stage, low immune function, mainly manifested as recurrent respiratory and digestive tract infections. 5, anemia, vitamin A deficiency will appear increased stored iron, peripheral serum iron decreased, similar to iron deficiency anemia of small cell hypochromic anemia. Vitamin D deficiency mainly causes vitamin D deficiency rickets.