Although vitamin A is probably best known for promoting and maintaining healthy eyesight, it has other important functions as well. One of its major contributions is to improve the body’s resistance to infection. It does this in part by maintaining the health of the skin, mucous membranes, and other surface linings (intestinal tract, urinary tract, respiratory tract) so that harmful bacteria and viruses can’t get into your body. Vitamin A also boosts immunity by enhancing the infection-fighting actions of the white blood cells called lymphocytes. Vitamin A is also vital to the growth of bones, the division of cells in your body, and to human reproduction.