Evaluation of Vitamin D Status in the Green Iguana (Iguana iguana): Oral Administration vs UVB Exposure

Abstract

Vitamin D is scarce in most foods, and technically is not a nutrient, but a hormone. Our ancestors obtained sufficient exposure of their skin to solar ultraviolet radiation B, 390-320 nm, (UV-B), the wavelengths that permit conversion of pre-vitamin D to vitamin D, to satisfy their requirements for vitamin D. In the United States, milk is fortified with vitamin D to assure adequate intakes, particularly since many believe that avoidance of the sun is an important safeguard against skin cancer. While estimates of dietary requirements for humans appear rational, we know very little about effective and safe levels of vitamin D for reptiles (1). This is a critical issue since both deficiency and toxicity can produce abnormal calcium and phosphorus metabolic responses. Long term feeding of vitamin D at 4,000 IU per kg of diet will produce signs of toxicity in some domestic animals (2).