The main manifestations of zinc deficiency in four-year-old babies: a. Decreased digestive function. Zinc deficiency can affect the taste buds cell renewal and salivary phosphatase activity, so that the tongue mucosa hyperplasia, keratinization incomplete, so that taste sensitivity is reduced, loss of appetite, anorexia and heterophagia. Second, the growth is backward. Zinc deficiency can lead to growth decline, growth retardation, short stature and delayed sexual development. Decreased immune function. Zinc deficiency may lead to impairment of T-lymphocyte function and susceptibility to infection. Delayed intellectual development. Zinc deficiency can cause impaired DNA and protein synthesis in brain cells, resulting in delayed intellectual development. V. Symptoms such as hair loss, rough skin, dermatitis, map tongue, recurrent mouth ulcers, delayed wound healing, night blindness, anemia, etc. are also likely to occur.