Like most reptiles, an iguana has a three-chambered heart with two atria, one ventricle, and two aortae with a systemic circulation.

Although they will consume a wide variety of foods if offered, green iguanas are naturally herbivorous and require a precise ratio of minerals (2 to 1 calcium to phosphorus) in their diet. It is important for captive iguanas to have a variety of leafy greens along with fruits and vegetables such as turnip greens, collards, butternut squash, acorn squash, mango, and parsnip.

The skin they are shedding has all the nutrients they may have lost growing their new skin, so why shouldn't they eat it?

The blue iguana (Cyclura lewisi) has the longest lifespan--25 to 40 years in the wild--with one specimen living 69 years in captivity.