Iodine in biology
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for iodine in 2000. For people age 14 and up, the iodine RDA is 150 μg/day; the RDA for pregnant women is 220 μg/day and the RDA during lactation is 290 μg/day. For children 1–8 years, the RDA is 90 μg/day; for children 8–13 years, 130 μg/day. As a safety consideration, the IOM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. The UL for iodine for adults is 1,100 μg/day. This UL was assessed by analyzing the effect of supplementation on thyroid-stimulating hormone. Collectively, the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
Puppy nutrition
To date, there is little information available about minimum requirements of dietary iodine for developing puppies. However, literature suggests that overdosage of iodine in puppies has deleterious effects on the thyroid gland. High dietary iodine may cause both hypothyroidism and changes in bone metabolism, considering that thyroid hormones are key factors in osteogenesis, as they stimulate osteoblasts, and promote collagen synthesis and mineralization of the osteoid. This is particularly important during juvenile development, as these hormones favor the action of growth hormone (GH) and its facilitator, insulin growth factor-1 (IGF-1) at the osteoplastic level. Hypothyroidism acquired at an early age presents a delay in the maturation and development of the ossification sites of newly-developing bone. It is therefore important to closely monitor the amount of iodine in puppy diets in order to prevent overdosage. The NRC states an adequate intake and recommended allowance of 900 μg/kg (DM) which translates into 220μg/1000 kcal. These values have been shown in multiple studies to be the recommended maximum allowance of iodine that would result in no abnormalities.