Vitamin A
Vitamin A is a fat soluble vitamin that aids in vision, reproduction, and the immune system. It also helps the kidneys, heart, lungs and other organs operate.
There are two kinds of vitamin A. The first type is preformed vitamin A. This type is found in meat, poultry, fish and dairy products.The second type of vitamin A is provitamin A. This type is found in fruits and vegetables. The most common form of provitamin A is beta-carotene.
How much vitamin A should an adult require? The FDA has establised a Daily Value for both types of vitamin A as 5,000 IU. Taking too much can be dangerous and adults should not take more than 10,000 IU per day. Most Americans get enough vitamin A from their food and deficiencies in it are very rare.
Here is a comprehensive fact sheet about vitamin A