Iodine requirements/recommendations

Iodide or iodate are used to iodize salt. The level of salt iodization depends on per capita salt consumption, moisture, light, heat, and contaminants. The recommended daily iodine requirements are 50 pg for infants, 90 pg for children (2-6 yrs), 120 pg for schoolchildren (7-12 yrs), 150 pg for adults and 200 pg for pregnant and lactating women. 

The normal daily iodine requirement is 65 to < 75 pg, equivalent to 1 pg kg body weight or to 220 pg I per kg consumed DM (Anke 2004a, Anonymous 1996). The daily recommended iodine intake is much higher, at 200 pg. 

The normative iodine requirement of adult humans is 1 pg I kg body weight. The recommended iodine intake is 2pgkg body weight (Anke etal. 2000), which corresponds with the WHO recommendation (Anonymous 1989). 

The recommended dietary iodine intakes represent amounts of iodine sufficient to prevent symptoms of deficiency and impairment of health or performance while maintaining the body s store of iodine (see sections Requirements/ Recommendations for Iodine Supplementation and Response Criteria and Dose—Response Studies of Iodine Requirement in Farm Animals ). Recommended daily... 

The requirements/recommendations for iodine supplementation vary between animal categories. To ensure an adequate iodine content in milk, lactating animals require more iodine than growing animals. 

Recently, a WHO technical consultation group met to review the maternal iodine requirements during gestation (Benoist et al, 2007). Consideration was given to the fact that the amount recommended should be sufficient to prevent brain damage or thyroid function disorders due to iodine deficiency during pregnancy. There is a lack of data to indicate an optimal intake. Therefore, conclusions were reached after evaluation of the efficiency of gut absorption of iodine, the estimated metabolic needs, and the typical daily losses in the feces and urine. 

The beneficial effects of iodine supplementation in the prevention and control of developed thyroid abnormalities due to iodine deficiency have been discussed so far in this chapter. However, supplementation with excess iodine, including the improvement of a previous iodine-deficient state, may cause thyroid dysfunctions, viz., iodine-induced hypothyroidism/iodide goiter in susceptible subjects (Roti and Vagenakis, 2000) and iodine-induced hyperthyroidism (IIH) especially in individuals over 40 years of age and who have been iodine deficient for a long period in the past (Vidor et ai, 1973). It may also increase the ratio of papillary/follicular carcinomas (Slowinska-Klencka et ai, 2002). In other words, both low and excess intake of iodine is related to further risk of thyroid disease. Although a daily intake of up to 1000 pg/day by a normal adult individual is quite safe (WHO, 1994), the upper limit is much lower in a population that has been exposed to iodine deficiency in the past. Therefore, to prevent IDD, the recommended iodine requirement in an adult individual is fixed within a narrow range of 150 rg/day (Knudsen et ai, 2000). Iodine supplementation under certain conditions in certain populations causes adverse effects, e.g., iodide goiter and iodine-induced hypothyroidism, IIH, iodine-induced thyroiditis and thyroid cancer. 

The First Latin American Conference on Nutrition, held in Montevideu (Uruguay) in July 1948, discussed many nutritional problems, and focused primarily on salt iodi-zation, both as a measure to meet human iodine requirements, and as a means to eradicate endemic goiter. It also discussed the legalization of this procedure and included a recommendation on the content of iodine that should be added to salt. 

Iodine requirements in the infant are not precisely known but it is efficiently absorbed and therefore the oral recommended dose is approximately the same as the intravenous dose. 

The FNB-NRC recommends that many added sources of iodine in the American food system, such as iodophors in the dairy industry, alginates, coloring dyes, and dough conditioners, be replaced wherever possible by compounds containing less or no iodine. This recommendation was prompted because the iodine consumed by human beings has increased in recent years, and there is evidence that the quantity of iodine presently consumed in the United States is well above the nutritional requirement. Although there is no direct evidence of an increased human iodine toxicity problem because of the increased intake, there is some concern that if this trend continues, the greater iodine concentration may contribute to an increase in thyroid disorders. 

The daily iodine requirement for prevention of iodine deficient goiter in adults is approximately 1 ig/kg weight, that is 50 to 75 pg/day. An allowance of 150 pg/day is recommended in order to provide an extra margin of safety and to meet increased demands that may be imposed by natural goitrogens under certain conditions... 

Directing the iodination reaction toward histidine residues in proteins, as opposed to principally tyrosine modification, is possible simply by increasing the pH of the lodobeads reaction from the manufacturer s recommended pH 7.0-8.2 (Tsomides et ai, 1991). No reducing agent is required to stop the iodination reaction as is the case with chloramine-T and other methods. 

The methods discussed produce trihalides of varying purity however, if very pure trihalides are required, they can be sublimed at high temperature from any oxide or oxohalide impurities. The trichlorides can usually be obtained pure, but the tribromides and triiodides tend to be contaminated with oxides and oxoiodides. The various methods of preparing triiodides are compared by a few authors 39, 40, 49, 132), and they recommend their preferred route, which generally is the direct reaction between the metal and iodine. 

These are classified as those with a requirement below one pg (microgram) per day. Elements in this class include boron, chromium, fluoride, iodine, molybdenum, nickel, selenium, cobalt and manganese. Cobalt is part of vitamin (see above). However, there appear to be no recommended dietary intakes for any of these except molybdenum. 

The last reagent is added as a moderator to prevent a runaway reaction nitrobenzene, or an alternative oxidant (iodine or chloroanil are often recommended), is required to convert the product, 1,2-dihydroquinoline, into quinoline. 

Starch-iodine complexation is temperature dependent. At 50°C, the color is only one-tenth as intense as at 25°C. If maximum sensitivity is required, cooling in ice water is recommended.20 Organic solvents decrease the affinity of iodine for starch and markedly reduce the utility of the indicator. 

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