Iodine content in foods

Rehable data on iodine content in foods can only be obtained by the careful performance of appropriate, accurate analytical methods carried out by trained analysts. The choice of the appropriate methods performed in the state of statistical control and under other quality control measures is the second crucial prerequisite to ensuring the quality of the results obtained. Obtaining a sufficiently homogeneous and representative sample is the third basic prerequisite for arriving at valid and meaningful analytical results. 

Table 75.1 Comparative iodine content in foods from two zones in india ((ig per tOOg of dry matter)...

Table 131.3 Iodine content in food samples from Bafoulab6, Kayes region...

The iodine content from food of plant origin is low in comparison to food of animal origin (Table 9-4.11). In Gentral Europe, foodstuffs rich in sugar and starch, such as cereals, pudding, honey, bread, rolls, rolled... 

Hassanein M, Anke M and Hussein L (2000) Determination of iodine content in traditional egyptian foods before and after a salt iodination programme. Pol J Food Nutr Sci 9 25-29. 

Various analytical techniques for the determination of different levels of total iodine or iodine species in foodstuffs and related materials are presently available. They differ in principles, equipment needed, detection limits, reliability, i.e., accuracy and precision of results, the ease of performance, sample throughput, and analysis cost. The choice of the most appropriate method largely depends on the purpose of the analysis, e.g., whether it concerns routine monitoring and/or screening or whether delicate certification of a foodstuff reference material is to be carried out. Obviously, one of the decisive parameters is whether the method s detection limit is sufficiently low for the given purpose. For this reason, it appears useful to give the typical iodine levels in various foods to facilitate the choice of the appropriate method(s). Table 2.5 lists the average iodine content of foods (fresh and dry basis), which was adapted from the data reported by Koutras et al. (1985). 

Because of the variability of iodine content in specialized enteral preparations, the iodine status of individuals should be monitored with prolonged use of these products and regular assessment of goiter, urinary iodine content, and thyroid function tested. Such monitoring is also appropriate if specialized enteral preparations are only part of the total nutritional intake, particularly if protein- and iodine-rich foods are restricted. 

Iodine status assessments should also be based on food production surveillance and prospective clinical studies measuring Ul, iodine content in daily diets and goiter prevalence. 

The iodine concentration in foods of all types varies considerably due to a number of factors, such as soil composition, animal breeding, climate, and other environmental variables. Moreover, the amount of iodine from each food depends on the source, preparation, processing and volume consumed. The iodine value for a food represents an average and does not consider the wide variations in the iodine content of the food hence some values, such as those from food composition tables, used in the evaluation of iodine intakes are likely to be subject to error. In addition, the use of food composition tables may be considered inappropriate to reasonably estimate iodine intake in groups of individuals consuming unconventional foods not listed, or inconsistently listed, in such tables. 

Iodine concentrations in foods and total diets are extremely variable depending on geochemical, soil and cultural conditions that influence the iodine uptake of staple crops and foods of animal origin. The iodine content of food ultimately depends on the concentration of iodine in the soil of the region in which the food is produced. Thus, in... 

The major natural food source of iodine is fish. The iodine content of fish reflects that of the water they inhabit thus, high levels of iodine are present in marine fish and shellfish compared to freshwater fish (Figure 45.1). Milk and dairy products contain relatively high amounts of iodine and are considered to be the most important sources of iodine in developed countries. The iodine content of milk is largely influenced by the use of iodophors as teat sterilants and equipment sanitizers in dairy husbandry, and the supplementation of animal feeds due to iodine deficiency in dairy cattle, exacerbated by the inclusion of goitrogenic feeds in the diet (COT, 2003). In addition, seasonal variations in the iodine content of foods are particularly evident in cows milk, with greater iodine... 

An increase in precision may be achieved by increasing the number of subjects, although more involved dietary assessment methods, such as the duplicate portion technique, are labor intensive and require a significant amount of subject commitment therefore, their use is usually restricted to small groups and data are collected over a short period of time (Petersen and Barraj, 1996). However, short time periods will miss any seasonal differences in the iodine content of foods that may occur. Seasonal variations were minimized in the Waldmann study, as 7-day FFQs were completed in both the autumn and spring seasons. 

Establishing links between acmal dietary iodine intake and iodine deficiency disorders relies on the availability of precise techniques to enable accurate estimation of nutritional intake. However, the evaluation of iodine intake is difficult, due to wide variations in the iodine content of food hence, obtaining an accurate assessment is not possible with food composition tables. This is particularly pertinent to vegans who consume a variety of unconventional foods not listed, or inconsistently listed, in such tables. 

The volume of food ingested by the infant is small, iodine content in formula preparations is insufficient, and parenteral nutrition does not supply enough iodine. This problem is not exclusive to Spanish premature babies, as the iodine content of many formulas in other countries is also inadequate. Therefore, supplements should be added if iodine intake is found to be inadequate. Breast milk appears to be the best source of iodine for the premature infant. 

Generally, the iodine content of foods varies across regions and countries, according to the amounts of naturally occurring iodine and the levels and extent of iodine supplementation in table salt, animal feed and processed foods. This is illustrated in Tables 54.3-54.5, which also reflect differences in reference tables used in various countries to describe the nutritional content of common foods (Krajcovicova-Kudlackova et al., 2003 Lightowler etal., 1996). 

The limited iodine salts available for use in food and beverages are potassium/sodium iodide, potassium/sodium iodate, or calcium iodide/iodate. Potassium iodide/iodate is the most widely used iodine salt in food and beverage formulations. Calcium salts are becoming less popular in food fortification because of their poor solubility and lower iodine content. 

As a result of changes in the iodine content of food products in the United States, iodine intake has varied over the years. 

Figures 116.1 and 116.2 show the estimated 24-h iodine excretion among users and nonusers of dietary supplements before and after fortification. They show that even among nonusers of dietary iodine supplements Hving in an area with low iodine content in groundwater and thereby a relatively low iodine intake, the iodine intake from food seems to be adequate after fortification.

The dietary associations were generally weak, but the true associations may have been masked by measurement error including that arising ffom intraindividual variation in spot measurements of urinary iodine. An individuals iodine concentration varies substantially day-to-day, due to the combined effects of circadian patterns of iodine excretion (Als et at, 2000), rapid renal clearance of dietary iodine following meals and inconsistency in the iodine content of food. We were able to average measures for children in the pre-intervention surveys who participated... 

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