What you feed your iguana will be directly related to their overall health and well-being. Green Iguanas are herbivores, that is, they are plant eaters. Animal proteins, such as dog food, cat food, and various “people food” treats should be avoided completely if possible. Iguanas do tend to like junk food, like pizza, but it is not good for them, and feeding them alot of food like this can lead to kidney failure at a young age. If you do feed your iguana “treats”, we’d recommend keeping it at a once per month MAXIMUM to be on the safe side. Kale, bok choy, broccoli, cauliflower, brussel sprouts, and other cabbage-related vegetables should be fed only in small amounts. These vegetables can cause thyroid problems if they are fed to your lizard frequently. Spinach should not be fed at all to an iguana, because it binds calcium.
Iguanas require a diet that is high in calcium, low in phosporous, and contains Vitamin D3. Greens should be the staple of the diet. By greens we mean, Collard greens, Mustard greens, Dandelion greens(you can pick these right out of your yard as long as they are not treated with pesticides and washed before feeding), Turnip greens, etc. Mixed vegetables, squash, zucchini, yams, raspberries & blackberries(high in calcium), bananas, and other fruits and vegetables or commercial iguana food can also be added, but the large majority of the diet should be greens. If your iguana is getting a proper diet than no extra vitamins really need to be added to the food.