Without these the iguana will die. This is why light is so important to iguanas. UVA rays are needed by plants and can be found in plant-growth lights. Reptiles require UVB rays to synthesize or make vitamin D3. Vitamin D can be acquired from food or from the exposure to the sun.
Vitamin D is needed for calcium metabolism by aiding in the absorption of calcium.
Vitamin D works hand in hand with Vitamin A. An absence of these vitamins can cause metabolic bone disease and other abnormalities. In your reptile enclosure it will be crucial that you have a UVB light, which can be turned on for an hour or two each day. Make sure there is both light and shade so the iguana can go back and forth. Adult iguanas can become aggressive and territorial when they reach sexual maturity. It is also important to remember the baby iguana that you buy at the pet store that starts out at six inches can grow to be four to six feet in length at adulthood.