Final answer:
Vitamin A does not help with the absorption of calcium and phosphorus; that is the role of vitamin D. Vitamin A's key functions include maintaining healthy epithelial cells.
Step-by-step explanation:
Vitamin A plays crucial roles in the body, but aiding in the absorption of calcium and phosphorus from the small intestine is a function of vitamin D, not vitamin A. The synthesis of vitamin D facilitates the absorption of calcium and phosphorus, important for bone health and maintenance of normal serum concentrations of these minerals. In addition to helping with calcium absorption, vitamin D increases the biosynthesis of calcium binding protein in the intestinal mucosal cells, essential for the transport of calcium through the intestine. However, vitamin A is vital for maintaining healthy epithelial cells, which form the lining of various structures within the body, including the eye, the respiratory tract, and the urinary tract.