What is the best diet for iguanas?

The foundation of keeping any iguana healthy and thriving in captivity rests almost entirely on replicating its natural, strictly herbivorous diet. ^[1][9] Unlike many common reptile pets, green iguanas require massive amounts of high-fiber vegetables, with very little room for fruit or any animal protein. ^[5][7] Getting this balance wrong is the single biggest threat to their long-term health, often leading to serious issues like Metabolic Bone Disease (MBD) or kidney failure. ^[1][5]

# Herbivore Foundation

Iguanas, particularly adult green iguanas, are folivores, meaning their primary food source in the wild consists of leaves, flowers, and fruits found in the forest canopy. ^[9] In a captive setting, the diet must mimic this structure: high in fiber, low in fat, and low in animal protein. ^[1][5] This contrasts sharply with diets sometimes recommended for omnivorous lizards, and understanding this difference is critical for long-term care. ^[3]

A common pitfall for new owners is overfeeding protein or relying too heavily on commercially prepared pellets. ^[2][7] While pellets can provide a baseline of nutrients, they should never replace the bulk of the diet, which must come from fresh produce. ^[7] An ideal meal plan should be centered around dark, leafy greens, which provide the necessary bulk and nutrients without the sugar load found in fruits. ^[1]

# Primary Produce

The majority of an iguana’s daily intake—often cited as 70% or more—should consist of dark, leafy greens. ^[5][7] These greens are essential because they offer the right balance of fiber and nutrients, especially calcium. ^[1]

The best staples to rotate through regularly include:

• Collard Greens ^[1][7]
• Turnip Greens ^[1][7]
• Mustard Greens ^[1][7]
• Dandelion Greens ^[1][7]
• Escarole ^[1][7]
• Endive ^[1][7]

Beyond the greens, other vegetables offer valuable variety. Squash varieties, such as butternut or acorn squash, are good additions, as are vegetables like green beans and sweet potatoes. ^[1][5] Introducing a wide variety helps ensure that the iguana receives a broad spectrum of vitamins and minerals that a limited selection might miss. ^[1] When preparing food, chopping or shredding the vegetables finely is usually recommended to make consumption easier for the lizard. ^[5]

Here is a sample guideline for daily intake composition, keeping in mind that rotation is key:

When considering the variety, it is helpful to think in terms of an alternating schedule rather than a fixed daily meal. For instance, one week might feature Collards and Turnip Greens as the primary base, while the next focuses on Dandelion and Mustard Greens, ensuring the lizard isn't reliant on one specific plant that might lack a trace element needed elsewhere. ^[1]

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# Sugar Caution

Fruits are often appealing to iguanas due to their bright colors and sweet taste, but they must be heavily restricted. ^[1][5] In the wild, fruit consumption is typically seasonal and makes up a very small percentage of the diet. ^[9] In captivity, feeding too much fruit—anything above about 10% of the diet, and often less—can lead to obesity, diarrhea, and digestive upset because the high sugar content throws off the gut flora. ^[1][5][7]

If you offer fruit, it should be used sparingly, perhaps as a tiny piece once or twice a week, or only after the iguana has consumed the vegetable portion of its meal. ^[7] Good choices, when used in moderation, include berries, melon, and papaya. ^[1]

# Avoid List

Just as important as knowing what to feed is knowing what not to feed. ^[8] Certain common vegetables contain compounds that actively interfere with nutrient absorption or are directly toxic. ^[8]

Spinach is a prime example that keepers must be wary of. ^[1][5] While it is green, spinach is very high in oxalates, which bind to calcium, preventing the iguana from absorbing this essential mineral even if it is present in the food. ^[1][7] High oxalate intake combined with low calcium leads directly toward MBD. ^[1]

Other items to strictly exclude or limit severely include:

• Iceberg Lettuce: Offers almost no nutritional value other than water content. ^[1][5]
• Rhubarb: Can be toxic. ^[1][8]
• Avocado: Considered toxic to many reptiles. ^[1]
• Most high-protein items: Including dog/cat food, eggs, or meat, which stress the kidneys and can lead to gout or calcium imbalances in adult herbivores. ^[1][3]

Furthermore, research into plants that may contain toxins is ongoing, and owners should always cross-reference any new vegetable with reliable veterinary sources before offering it. ^[8] A simple check against a list of common household and garden hazards is necessary to maintain a safe environment. ^[8]

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# Mineral Balance

Because captive iguanas cannot bask under the intense, unfiltered UV-B radiation found outdoors, supplementation is non-negotiable for most owners. ^[5][7] Vitamin D3 is required for the proper absorption of calcium, and if the light source is inadequate, this vitamin must be supplemented through diet. ^[1]

The most critical factor to manage is the Calcium to Phosphorus (Ca:P) ratio. ^[1][7] For a healthy adult iguana, the diet should aim for a ratio of at least 2:1, meaning there should be twice as much usable calcium as phosphorus. ^[1][7] Many vegetables naturally contain phosphorus but little calcium, which is why leafy greens are so important, and why supplementation is necessary. ^[7]

A common method involves dusting the prepared vegetable mix with a calcium supplement (often without D3) several times a week. ^[5] On other days, a multivitamin powder containing Vitamin D3 should be used. ^[5] If the enclosure has proper, high-output UVB lighting, the frequency of D3 supplementation may need to be adjusted based on veterinary advice, as excessive D3 can also be harmful. ^[7] An important distinction here is that an iguana eating a diet composed mostly of low-calcium items like fruit and iceberg lettuce will become calcium deficient even if it is heavily supplemented, because the sheer volume of the food is wrong; therefore, addressing the 80% vegetable base comes before the dusting routine.

# Life Stage Adjustments

While the overall philosophy remains herbivorous, there are minor adjustments needed as an iguana grows. ^[1] Juvenile iguanas have higher caloric and protein needs relative to their body size as they are growing rapidly. ^[1][3]

For young iguanas, it may be acceptable to offer very small amounts of animal protein, such as cooked, unseasoned chicken or insects, perhaps once or twice a week—though this practice is becoming less common as keepers emphasize a more strictly plant-based, high-fiber diet for all ages. ^[1][3] The overwhelming consensus points towards ensuring the juvenile diet is rich in calcium-containing greens to support rapid bone development and avoid MBD during this critical phase. ^[1]

As the iguana matures into an adult, the requirement for animal protein drops to zero. ^[1][9] The adult metabolism is set up to process large volumes of tough plant matter, and any heavy protein load risks long-term kidney damage. ^[1] The focus shifts entirely to maintaining that high-fiber, low-sugar vegetable base, ensuring adequate hydration, and maintaining proper supplementation protocols. ^[5][7]

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# Water Access

Regardless of age or the specific mix of vegetables offered, consistent access to fresh, clean water is essential. ^[1][5] Iguanas absorb a significant amount of their necessary water through their diet, but a shallow, large water dish that they can soak in and drink from should always be available. ^[5] Regular soaking or misting can also aid in hydration and shedding, but the water dish remains a constant requirement for good husbandry. ^[1]