8 - Iodine bioavailability

Abstract

Publisher Summary Iodine is an essential micromineral for all animal species, including humans. It occurs in plant tissues predominantly as inorganic iodide and is readily absorbed in this form from all segments of the intestinal tract. Few definitive studies of iodine bioavailability have been done since 1973. The current information is primarily from the work of Miller and his associates at the University of Tennessee with dairy cattle. Early studies have shown that either sodium iodide (NaI) or potassium iodide (KI), as supplemental sources of iodine, were effective in maintaining normal thyroid weights in rats fed with goitrogenic diets. Several researchers have used uptake of stable or radioactive iodine by the thyroid or other tissue as an indication of bioavailability of an iodine source. Injectable forms of iodized oils, as well as iodized oils administered orally, have served as effective sources of supplemental iodine in the reduction of endemic goiter in human populations. Iodine is unique in that stability of the carrier compound is of great importance. Goitrogenic substances present in feed or food are the most important factors influencing iodine bioavailability. Perchlorates and rubidium salts were known to interfere with iodine uptake by the thyroid. Sodium iodide, potassium iodide, and thylenediamine dihydriodide are well utilized by animals as sources of iodine. Calcium iodate and pemacalcium orthoperiodate are also of high bioavailability and have been shown to have greater physical stability. Potassium iodide or sodium iodide has usually served as the reference standard when comparative studies were conducted.