Green Iguana Captive Dietary Needs

Green Iguana Captive Diet

Authored by Shaun Dixon, of Iguanas of the World.

One of the most common questions regarding the Green Iguana (Iguana iguana) I get asked time and again is,

“What can I feed my Iguana?”

The importance of diet can’t be stressed enough with our pet reptiles. A large amount of reptile illness can often be rooted back to diet in some way. Whether it’s an over, or under provision of certain vitamins or minerals (see Calcium Conundrum for more on this topic). It can also be the inability to process them through factors surrounding the environment such as lighting and heating. It can all quite often come back to dietary related issues. There are many ‘care sheets’ out there which are fantastic stepping-stones. Sadly though, for many owners, they cannot find many of the mentioned food items.

Red Petunia

Healthy Variety, Including Red Petunia

Green iguanas Iguana iguana are natural herbivores, folivores and frugivores. This means a large percentage of their diets in the wild are compiled of leaves, shoots, flowers, buds, petals, and fruits. A herbivore feeding strategy is more complicated than a carnivore species of reptile such as a snake who gain all of their nutrition, from a ‘whole food source.’

In a study, ‘Optimal foraging of a herbivorous lizard‘, the green iguana in their natural environment, Wouter D. Van Marken Lichtenbelt, Œcologia (1993) 95:246-256: demonstrated that, comparisons between intake and biomass availability of the various food items, revealed the lizards were selective and changes in seasonal food availability, led to periodic switching of food plants. The extent to which, nutrient constraints determining iguana feeding ecology, were investigated.

Iguanas in the wild eat a wide and varied seasonal diet. Unfortunately, to complicate matters, many of the care sheets out there today have not been updated for a long time. I suspect part of the reason; for UK keepers at least, many of the foods suggested to feed, cannot be readily  bought in the areas they live. If they are here, they can be under different names, and unfortunately, it is human nature to take the most convenient route. But this can result in impacting the long-term health of Green Iguanas Iguana iguana, as Sean McCormack brought up on his blog 10 basic rules for keeping pet reptiles  

“reducing the amount of effort taken in providing a varied and appropriate diet for the animals in our care. We are already at a massive disadvantage in that replicating the diet of our reptile species in the wild, is virtually impossible. So we have to make a serious effort to provide the next best thing”

Preparing a Green Iguana Diet

Petunia & Geranium Petals

Petunia & Geranium Petals

The only diet I agree with, is the ‘wild’ diet. In recent years, my goal has been to mimic as close to their natural diet as possible. I don’t believe in taking the easiest and most convenient route; leaving micronutrients, mental health, stimuli, and possible other health and healing benefits yet to be discovered, to chance. This is why we should aim for a wider variety of foods, and making a very serious effort for our wonderful scaly companions. With a little research, carefully looking at food items, and what is available to forage or grow from seed. There is an enormous variety of plants available. Along with more recent developments made in some supplementation, nutritional needs can be met easier and more readily than ever before.

Unfortunately, many of the foods we may try to avoid like those with high oxalic acid, such as Spinach, and Swiss Chard, are also the food items required by these animals for other health reasons. So they shouldn’t be avoided.

Green Iguana Dietary Vitamin Intake 

Much Ado About Chameleons Author
Olimpia Martinotti compares the
All In One Vitamins

In captivity, most nutritionists agree for normal bone growth development with muscle and organs to function normally (such as the heart), the overall aim of the diet should range between a ratio of Calcium (Ca) 1: Phosphorus (Ph) 1:1 to 3:1. Most dietary care guides we see for reptiles therefore suggest aiming for a ratio of 2:1. *More on Calcium and Reptiles Owners must also be aware of nutritional antagonists such as oxalic acid. This substance has the ability to inhibit the dietary absorption of calcium and other trace minerals from the total diet. If you feed high oxalic acid content foods in excess, it could also pose a risk of oxalate salt build-up on the kidneys, and gall bladder.

Unfortunately, many of the foods we may try to avoid with oxalic acid, such as Spinach, and Swiss Chard, are also the food items required by these animals for other health reasons. So they can not, or should not, be avoided completely.

Iodine, Goitrogens, and Phytochemicals

Iodine, for example, is required for a healthy thyroid. The thyroid organ is responsible for the function and production of hormones. Many of the food items we feed on a regular basis, such as Collards and Turnip greens carry high amounts of goitrogens. Goitrogens are the substance naturally found in many plant foods. These substances can interfere with iodine uptake, therefore the hormonal balance of the reptile. Being high in goitrogens, care should be taken to ensure they are not fed these kinds of foods exclusively. This is where many of the foods high in oxalic acid can be beneficial, in moderation (Spinach for example). Phytochemicals, such as saponins, and tannins, are naturally found in vegetables, and plant foods. These substances, over time, can affect the formation of blood cells in high enough levels. Therefore, these plants should be balanced out with Vitamin A.

Pansy Variety, with Hibiscus

A Variety of Pansies, & Hibiscus

Vitamin A

Vitamin A can cause a serious overdose (hypervitaminosis A). Especially the synthetic fat soluble form. So aim to feed carotene based sources as a precursor of vitamin A. As the animal can synthesise what it needs and requires with no risk of overdosing also, be aware of high levels of Magnesium/ Potassium. These can cause the formation of ionic salts in the kidneys or gall bladder, and/or difficulty with proper osmoregulation and hydration.

  • Meet dietary requirements from all food groups.
  • Make the diet as close to natural as possible
  • Provide a balanced, and stimulus enriching colourful diet.

My Yearly Plan

My dietary aims will be 80-120 food varieties a year. With 53% of the total yearly diet being natural feed. Falling back only on Supermarket and Greengrocer food when little is abundant, or can’t be grown in the winter months.

  • 80 Leafy green varieties. Including Shrubs, vines, weeds, trees, herbs, and leafy green vegetables.
  • 10 Root vegetable varieties (aiming for one starch vegetable, 3 x weekly)
  • 10 Fruits.
  • 20 Flowers, buds, petals.
  • In the summer months aiming for 8-12 greens daily, 2 root vegetables, 1 fruit, and 2 flower and bud varieties.
  • In the winter months aiming for 6-8 greens daily, 2 root vegetables 1 fruit, and 2 flowers.

A yearly dietary plan example. 2016. With 120 food items.

 Iguana Annual Diet  
Spring GreensBasil leaves Crimson CloverButternut Squash
Nasturtium flowersHollyhock flowersMallow flowersSowthistle flowers
Squash blossomCactus flowersClover budsAlfalfa buds
Squash shootsRibwort PlantainSwiss ChardHibiscus flowers
Calendula leavesSowthistle leavesBeet GreensDandelion flowers
Petunia leavesWild GeraniumPumpkin leavesFuschia flowers
Fuschia leavesHollyhock leavesRadicchio leavesViola flowers
Pansie leavesMallow leavesRed gem lettucePansy flowers
Viola leavesDianthus leavesBaby leaf lettucePetunia flowers
Grape vineNasturtium leavesLittle gem lettuceApple
Prickly pear cactusMulberry leavesCurly Kale leavesStrawberries
Knapp weedBramble leavesBok Choi leavesBlackberries
ChickweedHibiscus leavesRomaine lettuceBlueberries
BindweedAsh tree leavesDandelion leavesRaspberry
Lemon thymeLime tree leavesCauliflower leavesOptunia
Plum leavesHawthorn leavesPumpkin leavesMulberries
Hazel leavesOreganoBrocoli leavesFigs
Willow leavesLemon balmSweetheart CabbagePapaya
Buddleia leavesDillChicory leavesMango
Stinging NettleCurly Leaf parsleyRadish leavesSoy Bean
HawkweedFlat leaf parsleyPea-shoot leavesBrocoli
VetchCorianderEndive leavesAsparagus
HawkbitTarragonEscarole leavesGreen beans
Cow ParsleySageWatercressRunner Beans
Sticky WillyTymeMizuna MustardMangetout
Field ThistleRosemaryHedge Mustard leavesSugar Snap peas
Milk ThistleMarjoram leaves Giant Red MustardBell Peppers
PurslaneMethi LeavesAlfalfa/Lucerne GreensChopped Okra
Salad BurnetMint leavesArugula greens

Every Year, aims are to rotate other foods around into the diet, in replacement of other foods.

Primrose variety

A Primrose Variety

Next year, I aim to feed a different variety of flowers and leaves, and replace some of the trees and shrubs, for vines of other varieties. Along with growing some of my own natural varieties of course. Amaranth, will be included, the green variety, as per recommendation on growth trials by S Donoghue, Growth and Morphometrics of Green iguanas (Iguana iguana), with more focus toward legumes, beans and peas for the plant protein content needed for the 26% growth in younger specimen.

This diet list however is not exclusive. Nor is it the only amounts of foods that can be fed.


With my Supplementation. It is fed on a rotation.

  • 1st Monday-Wednesday of every month, Verm X.
  • Monday Multivitamin + (Alfalfa dust, if no fresh)
  • Tuesday Calcium Carbonate + Bee Pollen.
  • Wednesday Multivitamin + (Alfalfa dust, if no fresh)
  • Thursday Calcium Carbonate, and Manuka Honey.
  • Friday Multivitamin (Alfalfa dust, if no fresh)
  • Saturday and Sunday, (no supplementation) but with additional focus on hydration and fibre of last-minute food items, stalks and stems.

For further suggestions on what green iguanas can eat, or if you wish to learn how to forage certain food items, many of the tortoise care websites can be helpful, and quite often what is safe for tortoises is often safe for other ‘hindgut fermenters‘ (Melissa Kaplan gives a great overview of hindgut fermentation), like iguanas.

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