Vitamin A is a group of compounds that aid in vision, reproduction, cell division, bone growth, and cell differentiation (in which a cell becomes part of the brain, muscle, lungs, blood, or other specialized tissue.) Vitamin A helps to regulate the immune system, which helps prevent or fight off infections by making white blood cells that destroy harmful bacteria and viruses. Vitamin A may also help lymphocytes, which are a type of white blood cell, fight infections more effectively. Vitamin A promotes healthy surface linings of the ex and the urinary, respiratory, and intestinal tracts. If those linings break down, it becomes easier for bacteria to enter the body and cause infection. Vitamin A also helps mucous membranes and skin function as a barrier to bacteria and viruses.
Vitamin E is found naturally in certain foods, added to others, and available as a dietary supplement. "Vitamin E" is the collective name for a group of fat-soluble compounds that have distinctive antioxidant activities. Serum concentrations of vitamin E (alpha-tocopherol) depend on the liver, which takes up the nutrient after various forms are absorbed from the small intestine. The liver preferentially resecretes only alpha-tocopherol via the hepatic alpha-tocopherol transfer protein, and the liver metabolizes and excretes the other vitamin E forms. As a result, blood and cellular concentrations of other forms of vitamin E are lower than those of alpha-tocopherol and have researched less. Antioxidants protect cells from the damaging effects of free radicals, molecules that contain an unshared electron. Free radicals damage cells and may contribute to the development of cancer and cardiovascular disease. Unshared electrons are very energetic and react rapidly with oxygen to form reactive oxygen species (ROS). The body forms ROS endogenously when it converts food to energy, and antioxidants may protect cells from the damaging effects of ROS. The body is also exposed to free radicals from environmental exposures, such as air pollution, cigarette smoke, and ultraviolet radiation from the sun. ROS is part of the signaling mechanisms among cells. Vitamin E is a fat-soluble antioxidant that stops the production of ROS that is formed when fat undergoes oxidation. Scientists are investigating whether, by limiting free-radical production and possibly through other mechanisms, vitamin E might aid in preventing or delaying the chronic diseases associated with free radicals.
Beta Carotene is a substance found in carrots, apricots, sweet potatoes, pumpkin, cantaloupe, winter squash, mangos, collard greens, spinach, kale, broccoli, and other oranges, red, and dark green fruits and vegetables. It is a carotenoid that may be made into vitamin A in the body. It is most efficiently made into retinol. Alpha-carotene and beta-cryptoxanthin are converted to vitamin A as well, but only half as efficiently as beta-carotene.
