Optimal Iodine Intake

Thyroid Factor

The Natural Thyroid Diet

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The recommended daily iodine intake is variable depending the age of the subject (table 1). The recommended intake of iodine in neonates reflects the observed mean iodine intake of young infants exclusively fed human milk in iodine-replete areas [4, 5]. However, it is well established that the iodine content of breast milk is critically influenced by the dietary intake of the pregnant and lactating mother [4, 5]. The iodine intake required in order to achieve a positive iodine balance and to insure a progressively increasing intrathyroidal iodine pool in the growing infant is at least 15 |xg/kg/day in full-term and 30 |xg/kg/day in preterm infants; this corresponds approximately to 90 |xg/day [6].

These recommendations derive from consensus statements by several groups, including the International Council for Control of Iodine Deficiency Disorders, the World Health Organization, UNICEF, and the Food and Nutrition Board of the US National Academy of Sciences. The amounts are based on the following: the calculated daily thyroid hormone turnover in euthyroidism, the iodine intake producing the lowest values for serum thyrotropin (TSH) and for serum thyroglobulin (TG), the amount of thyroid hormone replacement necessary to restore euthyroidism to athyreotic subjects, the iodine intake associated with the smallest thyroid volumes in populations, and the lowest incidence of transient hypothyroidism in neonatal screening with blood spot TSH. About 90% of iodine is eventually excreted in the urine. The median urinary iodine concentration in casual ('spot') samples, expressed as micrograms per liter (^g/l), is currently the most practical biochemical laboratory marker of community iodine nutrition. It is more useful and much simpler than measuring 24-hour samples or calculating urinary iodine/creatinine ratios. Recommendations by the International Council for the Control of Iodine Deficiency Disorders, WHO, and UNICEF [9] set 100 |xg/l as the minimal urinary iodine concentration for iodine sufficiency. This figure corresponds roughly to a daily intake of 150 |xg iodine. The upper limit for safe iodine intake is uncertain and varies widely among individuals and populations. Occasional intake up to 1 mg iodine per day may be safe for most people, and much higher amounts are usually tolerated for a brief period of time, without major problems.

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