When people call with problem iguanas, I always ask what they are feeding their iguanas. The answer, invariably, is "Vegetables." When I ask what kind of vegetables, the response ranges from "Well, you know, just...vegetables!" to something along the lines of, "Oh! Lettuce, zucchini, broccoli and once a week or so, a little bit of fruit."

The fact that iguanas can survive for years on a lousy diet makes it all the more difficult for people to grasp that the diet they are feeding their iguana (often coupled with improper environmental conditions) is making their iguana sick and affecting its growth and development.

Your mom or dad probably nagged you to "eat your vegetables!" Since two of my mother's favorite food groups were Coca-Cola® and See's® Candies, she didn't do much in the way of vegetable nagging. My dad was the veggie and fruit nagger. As it turns out, he was right, although my mom's diet was a lot more fun.

The mainstream and health news over the past decade has been full of reports from researchers finding that certain vegetables and fruits may help reduce the risks of certain types of cancer and a variety of other diseases and disorders. Consuming of a wide range of vegetables and fruit on a daily or aggregate weekly basis is healthier, reports say, than a diet based primarily on animal protein and grains and tubers.

When humans follow these dietary guidelines, we consume a variety of foods during the course of a day, week, and month. In this way, the individual vegetables and fruits we eat form only a small part of our total diet, not the primary ingredient (unless you are like me when artichokes and blueberries are in season). So, even if we concentrate on the many vegetables and fruits that are high in antioxidants, individually these plants will still be a part of a much larger diet and so are unlikely to result in the nutrition-related disorders that could result if we ate just a few plants exclusively.

This is essentially how a wild iguana eats. Throughout the course of a year, more than 50 different types of plants will be eaten, providing a wide variety over time, though selections may be somewhat more limited on a season-by-season basis. Iguanas have been documented to travel great distances to get to a particular type of plant, by-passing plants lower in protein (and ignoring small animals and carrion) on their way to those sought-out plants and when returning to their usual basking and sleeping areas.

Falling Into a Rut

Lack of recognizing or understanding the many facets that go into constructing a proper diet for iguanas, combined with trying to keep things as easy or quick as possible, leads many owners into offering a very limited selection of food on an ongoing basis. Plants that have the potential for causing harm if eaten as a significant part of diet don't cause problems for the vast majority of humans because we eat these foods as a small part of a much larger, varied diet. Make these problematic plants the main source of food for humans or iguanas and the problems that those foods can cause will manifest. The convenience and lack of understanding dietary needs and pitfalls is why we see iguanas who are fed on things that people can quickly cut up or pull out of a bag. Broccoli florets and Brussels sprouts are two vegetables that are easily cut into small pieces for iguanas. Bags of pre-washed Spring Greens (which are small leaves of mostly lettuce-type plants) and baby spinach are commonly used or, worse, the bags of iceberg mixed with a few carrot and red cabbage shreds.

When these harmful and mostly low-in-nutrient foods are combined with the equally convenient soaked monkey biscuit, and maybe some kale (all the books list kale as one of the high calcium greens), you get not a healthy iguana, but one that is stunted and lethargic. These iguanas are also usually deficient in calcium though their owners may not yet have observed the signs. Contributing to the owner's conclusion that their iguana is doing well is the fact that many of these iguanas have great color and got tame very fast. In fact, their iguanas are malnourished, suffering from hypothyroidism, and on their way to metabolic bone disease.

There are sevral phytochemicals known to impair iodine uptake or otherwise contribute to the formation of goiter, which is the enlargement of the thyroid gland caused by inadequate iodine uptake. People--and iguanas--may have hypothyroism without their thyroid gland being so swollen that it is clearly visible as a swelling protruding from their neck.

When fed in excess, broccoli, Brussels sprouts, kale, cabbage, cauliflower, and bok choy, and soy cause hypothyroidism. This disordrer causes the metabolic rate to slow down, lethargy, and muscle and joint aches. The slowed metabolism and reduced activity leads to weight gain, but overall growth and development is slowed. These vegetables may be fed in small amounts in addition to the regular vegetables, mixed into their salad, but should never become the primary ingredients or regular additions to the diet.