The Effects of Calcium-Binding Vegetables for Lizards

Meeting the nutritional needs of a pet lizard is one of the most difficult aspects of lizard husbandry. One of the primary challenges is providing enough calcium in a captive lizard̵7;s diet. Unfortunately, some vegetables can undermine these efforts and lower a lizard̵7;s calcium levels.

  1. Calcium and Lizard Biology

    • Calcium is important for lizard̵7;s muscle performance, metabolism, and developing and maintaining strong bones. Female lizards of many species use high quantities of calcium when producing eggs. In order to use ingested calcium, lizards must have enough activated vitamin D, also termed D3, in their systems. When lizards are exposed to light in the UVB portion of the spectrum, their bodies converts vitamin D to its active form.

    Challenges of Captivity

    • In captivity, many of the fruits and insects fed to lizards are deficient in calcium. Overcome this by selecting foods high in calcium as dietary staples, like collard greens and dandelions. Additionally, you can add calcium supplements to the lizard̵7;s food two or three times per week to make up for any deficiencies. Supply UVB radiation by providing full-spectrum reptile lights or regular access to natural, unfiltered sunlight.

    Calcium-Binding Vegetables

    • Even a keeper who provides UVB light properly, offers calcium rich vegetables and supplements regularly can cause her lizard to have a calcium deficiency. Calcium-binding vegetables are high in calcium but are also high in oxalic acid or oxalates. Oxalates bind together with calcium, inhibiting absorption. Over time, a diet high in oxalates can lead to low levels of calcium in the blood -- despite the fact that the lizard̵7;s diet was made up of high-calcium foods. If fed occasionally, high-oxalate foods pose little risk, but you shouldn̵7;t feed such foods as part of the regular diet. Spinach, broccoli, kale, grapes, cilantro, pears and strawberries are high-oxalate items frequently offered to green iguanas (Iguana iguana) and other lizards.

    Other Dietary Roadblocks

    • In addition to vegetables high in oxalates, foods with high levels of phosphorus can inhibit calcium absorption. The ratio of calcium to phosphorus in the animal̵7;s diet should be 2-to-1. A diet high in fat can also reduce available calcium by reducing the calcium's solubility and therefore its absorption.

    Effects of Low Calcium

    • When a lizard̵7;s calcium levels drop, the body pulls reserve calcium from the bones. This causes a condition termed metabolic bone disease, or MBD. It is a serious, largely untreatable condition. MBD results in swollen, soft or misshapen bones; digestive malfunction; muscle tremors; and weakness, and it can lead to egg-binding in gravid females. Some juvenile lizards with MBD retain their juvenile head shapes or exhibit stunted growth as a result of improper hormone production, due to low calcium levels in the blood.

    Recommended Vegetables

    • Though variety is clearly the key to a balanced diet, some foods should be staples of most lizard diets. Collard greens, mustard greens, turnip greens, snap peas, dandelion, alfalfa, watercress, endive and prickly pear cactus leaves ̵1; with the thorns removed ̵1; should form the bulk of the diet. All of these vegetables are low in oxalates and have excellent calcium-to-phosphorus ratios.