Iodine intake States

In 1985, to combat iodine deficiency in the former state of East Germany, salt for human consumption was iodized and iodine was added to animal feed (Anke et al., 1993). Eliminating iodine deficiency in farm animals improved the iodine content of milk and eggs. This further increased the dietary iodine intake of East Germans (see section The Effect of Iodine Intake on the Iodine Gontent of Eggs, Meat and Milk ). The program successfully reduced iodine deficiency in both humans and farm animals, and could be used as a model for iodine supplementation in other countries. 

Several authors (Rasmussen et al, 2001 Knudsen et al, 2002 Voelzke et al, 2003) stated that food questionnaires are refiable instruments to assess a population s iodine intake. However, there are indications that self-estimations concerning iodine intake recorded on a diary card are unreliable when compared with iodine intakes obtained by direct analysis of real diets (Lightowler and Davis, 2002). 

Previous studies investigating dietary intake of micronutrients have reported that the dupficate portion technique offers the most accurate estimation. A study comparing dietary assessment methods to measure selenium intake concluded that diet record assessment was not adequate for predicting selenium intakes of individuals, and that duplicate diet analysis remains the recommended measure for research purposes (Duffield and Thomson, 1999). Furthermore, Koutras et al. (1970) state that if iodine intake is to be measured, the best method is the dupficate portion technique. However, the dupficate portion technique is labor intensive and requires a significant amount of subject commitment therefore, its use is usually restricted to small groups and data are usually collected over a short period of time. 

Previous studies assessing iodine intake in vegans have estimated intake from dietary supplements based on manufacturers declarations. Therefore, such intakes may be considered an approximation, as analysis has shown that the iodine content may differ from that stated on the packaging of the supplements and may also vary from tablet to tablet. 

The autoimmune prone BB-DP rat, on the other hand, more easily developed AITD under the influence of a diet rich in iodine, depending on the previous state of the thyroid (Ruwhof and Drexhage, 2001). In severe ID, those animals had less severe lymphocytic thyroiditis and the production ofTg-Ab was depressed, probably as part of a general lowering of thyroid autoimmunity induced by severe ID. The results obtained with these different strains of rats may be viewed as a model for the individual heterogeneity in response to changes in iodine intake. 

Notes In a comparison of the clinical characteristics at baseline in the patients with iodine restriction, the pretreatment iodine intake in the recovery group (patients who recovered from hypothyroidism to the euthyroid state spontaneously after 12-week iodine restriction) tended to be higher than that of the nonrecovery group (patients who did not recover from hypothyroidism to the euthyroid state after 12-week iodine restriction), but the difference was not statistically significant. ... 

It can be seen in Figure 78.6 that the incidence of thyroid cancer (all forms) is at the same level today as in 1971, with about 4.6 (women) and 2.0 (men). The overall thyroid cancer incidence in Sweden is somewhat higher than the incidence reported from the UK (number of cases/100000/year) 1.4 (men) and 3.7 (women), respectively (Office for National Statistics Registrations, UK, 2006) but clearly lower than that reported in the United States 4.3 (men) and 12.5 (women), respectively. In the US, an increase in incidence of about 4.8% was observed from 1992 to 2002 National Cancer Institute. The increase in thyroid cancer incidence has been postulated to be correlated with an increased iodine intake in a population. There is a suggested increase in thyroid cancer of the papillary type about 20 years after the... 

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 response to thionamides depends on the dose and environmental iodine intake. It occurs faster in subjects living in countries with moderately low iodine intake than in areas with iodine deficiency. Antithyroid drug doses should be gradually decreased to the minimal maintenance dose as serum thyroid hormone levels fall. The aim is to restore the euthyroid state within 1-2 months. 

Development of iodine-induced thyroid dysfunction is influenced by a person s prior iodine intake. Cases of thyrotoxicosis being induced by contrast media are mainly reported in Europe or Australia, where dietary iodine levels are low, as described by Fradkin and Wolff (1983). Except for cases due to amiodarone, the incidence of iodine-induced hyperthyroidism is very low in regions where dietary iodine is adequate (Roti and degfl Uberti, 2001). Neonates treated with PVP-I often develop hypothyroidism in iodine-insufficient regions of Europe, but rarely do so in iodine-sufficient regions of the United States, as described by Brown et al. (1997). Thus, persons who five in areas where iodine is deficient in the diet are at risk of developing thyroid dysfunction induced by iodine-containing pharmaceuticals. 

As is discussed elsewhere in this volume, the United States is considered an iodine-replete nation. Although iodine intake may be decreasing, iodine insufficiency is not thought to be a cause of hypothyroidism or goiter in the United States. Therefore, in this chapter we will review... 

Iodine deficiency was common worldwide. Some countries in Europe, Asia, Africa and some states of Australia are still iodine deficient despite major national and international efforts to increase iodine intake, primarily through the voluntary or mandatory iodization of salt. 

The two most recent NHANES surveys showed that for women of childbearing age and pregnant women, the median UI excretion levels were adequate (127 and I4lpg/1, respectively, in 1988-1994 132 and 173 pg/1, respectively, in 2001-2002) (Table 115.3) (Caldwell et al., 2005). Thyroid hormone, requiring adequate iodine intake, is critical for neural development in utero and in early life. Although cretinism due to iodine deficiency is not a problem in the United States, subtle developmental delays could result from mild maternal iodine deficiency. 

An increase in iodine intake is only the first step in the amehoration of iodine deficiency. The increase must be sustained, which has not always been the case. In the United States, iodine supplementation of salt and other foods has never been mandated by the government. Furthermore, the iodine content of most foods is not listed on package labels. The last market basket analysis for US iodine intake was conducted in 1982—1994, and reported in 1996 (Pennington and Schoen 1996). Public awareness of the primary sources of iodine in the US diet and its importance in our daily diet has not been stressed. 

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