Beta Carotene is converted into Vitamin A in the body. It performs antioxidant functions which regular Vitamin A does not. Beta Carotene and Vitamin A are essential for the maintenance of healthy epithelial tissue, which is found in the eyes, skin, respiratory system, GI, urinary and urinary tracts.

In standardised supplementation, every 0.0006 mg of Beta Carotene is equivalent to 1 IU of Vitamin A.

eg. 15mg = 25,000 IU

Article: http://www.umm.edu/altmed/articles/beta-carotene-000286.htm