The most important function of vitamin A in the body – is part in the process of vision. Vitamin A is part of the visual pigment – rhodopsin, which converts the incident light to the retina of the eye into electrical impulses, which are going to the brain and create a visual image. Furthermore, vitamin A is needed for healthy skin, has a positive effect on the endocrine and immune systems and is crucial for the fertility. One of the earliest manifestations of vitamin A deficiency is a decrease in visual acuity in low light, up to complete its loss in the twilight (“chicken blindness”). Vitamin A deficiency is the leading cause of blindness in developing countries and contributes to the high level of child mortality from infectious diseases. Lack of this vitamin during pregnancy can cause serious birth defects of the child. Vitamin A is contained in butter, whole milk and cheese. Natural substance of Beta-carotene is also an important source of vitamin A .