Maria Andersson

Global Iodine Status in 2011 and Trends over the Past Decade

Salt iodization has been introduced in many countries to control iodine deficiency. Our aim was to assess global and regional iodine status as of 2011 and compare it to previous WHO estimates from 2003 and 2007. Using the network of national focal points of the International Council for the Control of Iodine Deficiency Disorders as well as a literature search, we compiled new national data on urinary iodine concentration (UIC) to add to the existing data in the WHO Vitamin and Mineral Nutrition Information System Micronutrients Database. The most recent data on UIC, primarily national data in school-age children (SAC), were analyzed. The median UIC was used to classify national iodine status and the UIC distribution to estimate the number of individuals with low iodine intakes by severity categories. Survey data on UIC cover 96.1% of the worlds population of SAC, and since 2007, new national data are available for 58 countries, including Canada, Pakistan, the U.K., and the U.S.. At the national level, there has been major progress: from 2003 to 2011, the number of iodine-deficient countries decreased from 54 to 32 and the number of countries with adequate iodine intake increased from 67 to 105. However, globally, 29.8% (95% CI = 29.4, 30.1) of SAC (241 million) are estimated to have insufficient iodine intakes. Sharp regional differences persist; southeast Asia has the largest number of SAC with low iodine intakes (76 million) and there has been little progress in Africa, where 39% (58 million) have inadequate iodine intakes. In summary, although iodine nutrition has been improving since 2003, global progress may be slowing. Intervention programs need to be extended to reach the nearly one-third of the global population that still has inadequate iodine intakes.

Prevention and control of iodine deficiency in pregnant and lactating women and in children less than 2-years-old: conclusions and recommendations of the Technical Consultation

The Consultation reached a general consensus on several important issues. First, that universal salt iodisation‡ (USI) remains the key strategy to eliminate iodine deficiency disorders. Second, that where USI has been effective for at least 2 years, with salt adequately iodised and consumed by more than 90% of the population 1 , it can be reasonably expected that the iodine needs of women of child-bearing age and pregnant and lactating women are covered by their diet, and that the iodine stored in the thyroid gland is sufficient to ensure adequate hormone synthesis and secretion. Third, that iodised salt may not provide enough iodine to meet a child’s needs during complementary feeding, especially if the mother is only marginally iodine sufficient, unless complementary foods are fortified with iodine. It may be necessary therefore to give additional iodine to makesure that requirements are met until such time as the child starts to eat the normal family food. Finally, there was consensus that monitoring of both iodised salt quality and iodine nutrition are important to ensure that an optimal state of iodine nutrition is reached and then sustained. The Consultation made several specific recommendations concerning requirements, indicators and strategies to control iodine deficiency disorders in pregnant and lactating women, and in children less than 2-years-old.

Iodine deficiency in 2007: Global progress since 2003

Background Iodine deficiency is a global public health problem, and estimates of the extent of the problem were last produced in 2003. Objectives To provide updated global estimates of the magnitude of iodine deficiency in 2007, to assess progress since 2003, and to provide information on gaps in the data available. Methods Recently published, nationally representative data on urinary iodine (UI) in school-age children collected between 1997 and 2006 were used to update country estimates of iodine nutrition. These estimates, alongside the 2003 estimates for the remaining countries without new data, were used to generate updated global and regional estimates of iodine nutrition. The median UI was used to classify countries according to the public health significance of their iodine nutrition status. Progress was measured by comparing current prevalence figures with those from 2003. The data available for pregnant women by year of survey were also assessed. Results New UI data in school-age children were available for 41 countries, representing 45.4% of the worlds school-age children. These data, along with previous country estimates for 89 countries, are the basis for the estimates and represent 91.1% of this population group. An estimated 31.5% of school-age children (266 million) have insufficient iodine intake. In the general population, 2 billion people have insufficient iodine intake. The number of countries where iodine deficiency is a public health problem is 47. Progress has been made: 12 countries have progressed to optimal iodine status, and the percentage of school-age children at risk of iodine deficiency has decreased by 5%. However, iodine intake is more than adequate, or even excessive, in 34 countries: an increase from 27 in 2003. There are insufficient data to estimate the global prevalence of iodine deficiency in pregnant women. Conclusions Global progress in controlling iodine deficiency has been made since 2003, but efforts need to be accelerated in order to eliminate this debilitating health issue that affects almost one in three individuals globally. Surveillance systems need to be strengthened to monitor both low and excessive intakes of iodine.

Assessment of iodine nutrition in populations: past, present, and future

Iodine status has been historically assessed by palpation of the thyroid and reported as goiter rates. Goiter is a functional biomarker that can be applied to both individuals and populations, but it is subjective. Iodine status is now assessed using an objective biomarker of exposure, i.e., urinary iodine concentrations (UICs) in spot samples and comparison of the median UIC to UIC cut-offs to categorize population status. This has improved standardization, but inappropriate use of the crude proportion of UICs below the cut-off level of 100 µg/L to estimate the number of iodine-deficient children has led to an overestimation of the prevalence of iodine deficiency. In this review, a new approach is proposed in which UIC data are extrapolated to iodine intakes, adjusted for intraindividual variation, and then interpreted using the estimated average requirement cut-point model. This may allow national programs to define the prevalence of iodine deficiency in the population and to quantify the necessary increase in iodine intakes to ensure sufficiency. In addition, thyroglobulin can be measured on dried blood spots to provide an additional sensitive functional biomarker of iodine status.

Global Iodine Nutrition: Where Do We Stand in 2013?

BACKGROUND Dietary iodine intake is required for the production of thyroid hormone. Consequences of iodine deficiency include goiter, intellectual impairments, growth retardation, neonatal hypothyroidism, and increased pregnancy loss and infant mortality. SUMMARY In 1990, the United Nations World Summit for Children established the goal of eliminating iodine deficiency worldwide. Considerable progress has since been achieved, largely through programs of universal salt iodization. Approximately 70% of all households worldwide currently have access to adequately iodized salt. In 2013, as defined by a national or subnational median urinary iodine concentration of 100-299 μg/L in school-aged children, 111 countries have sufficient iodine intake. Thirty countries remain iodine-deficient; 9 are moderately deficient, 21 are mildly deficient, and none are currently considered severely iodine-deficient. Ten countries have excessive iodine intake. In North America, both the United States and Canada are generally iodine-sufficient, although recent data suggest pregnant U.S. women are mildly iodine-deficient. Emerging issues include discrepancies between urinary iodine status in pregnant women compared to school-aged children in some populations, the problem of re-emerging iodine deficiency in parts of the developed world, the importance of food industry use of iodized salt, regions of iodine excess, and the potential effects of initiatives to lower population sodium consumption on iodine intake. CONCLUSIONS Although substantial progress has been made over the last several decades, iodine deficiency remains a significant health problem worldwide and affects both industrialized and developing nations. The ongoing monitoring of population iodine status remains crucially important, and particular attention may need to be paid to monitoring the status of vulnerable populations, such as pregnant women and infants. There is also need for ongoing monitoring of iodized salt and other dietary iodine sources in order to prevent excess as well as insufficient iodine nutrition. Finally, it will be essential to coordinate interventions designed to reduce population sodium intake with salt iodization programs in order to maintain adequate levels of iodine nutrition as salt intake declines.

P2 Receptor Expression Profiles in Human Vascular Smooth Muscle and Endothelial Cells.

P2 receptors mediate the actions of the extracellular nucleotides ATP, ADP, UTP, and UDP, regulating several physiologic responses including cardiac function, vascular tone, smooth muscle cell (SMC) proliferation, platelet aggregation, and the release of endothelial factors. P2 receptor characterization has been hampered by the lack of selective antagonists. The aim of the current study was to investigate the mRNA and protein expression of P2X and P2Y receptors in human SMC and in endothelial cells (EC). Smooth muscle cells were obtained from human mammary artery and EC from human umbilical vein. Using real-time PCR, the authors established quantitative mRNA assays. Protein expression was studied using Western blotting with recently developed antibodies. The P2X1 receptor was highly specific for human SMC, while the P2X4 was the highest expressed receptor in EC. The P2Y2 receptor was present in both SMC and EC. UTP-mediated effects in these cells are likely to be mediated by P2Y2 and not P2Y4 receptors since the latter had considerably lower expression. The P2Y6 receptor was expressed in both SMC and EC. The P2Y1 and surprisingly the P2Y11 receptors were the most abundantly expressed P2Y receptors in the endothelium. Overall, Western blotting confirmed the mRNA findings in most aspects, and most interestingly, indicated oligomerization of the P2Y1 receptor that may be important for its function. In conclusion, P2X1, P2Y2, and P2Y6 are the most expressed P2 receptors in SMC and are thus probably mediating the contractile and mitogenic actions of extracellular nucleotides. The P2X4, P2Y11, P2Y1, and P2Y2 are the most expressed P2 receptors in EC, and are most likely mediating release of nitric oxide, endothelium-dependent hyperpolarizing factor (EDHF), and t-PA induced by extracellular nucleotides. These findings will help to direct future cardiovascular drug development against the large P2 receptor family.

Ten Repeat Collections for Urinary Iodine from Spot Samples or 24-Hour Samples Are Needed to Reliably Estimate Individual Iodine Status in Women

Although the median urinary iodine concentration (UIC) is a good indicator of iodine status in populations, there is no established biomarker for individual iodine status. If the UIC were to be used to assess individuals, it is unclear how many repeat urine collections would be needed and if the collections should be spot samples or 24-h samples. In a prospective, longitudinal, 15-mo study, healthy Swiss women (n = 22) aged 52-77 y collected repeated 24-h urine samples (total n = 341) and corresponding fasting, second-void, morning spot urine samples (n = 177). From the UIC in spot samples, 24-h urinary iodine excretion (UIE) was extrapolated based on the age- and sex-adjusted iodine:creatinine ratio. Measured UIE in 24-h samples, estimated 24-h UIE, and UIC in spot samples were (geometric mean ± SD) 103 ± 28 μg/24 h, 86 ± 33 μg/24 h, and 68 ± 28 μg/L, respectively, with no seasonal differences. Intra-individual variation (mean CV) was comparable for measured UIE (32%) and estimated UIE (33%). The CV tended to be higher for the spot UIC (38%) than for the estimated 24-h UIE (33%) (P = 0.12). In this population, 10 spot urine samples or 24-h urine samples were needed to assess individual iodine status with 20% precision. Spot samples would likely be preferable because of their ease of collection. However, the large number of repeated urine samples needed to estimate individual iodine status is a major limitation and emphasizes the need for further investigation of more practical biomarkers of individual iodine status.

Update on iodine status worldwide.

Purpose of reviewSalt iodization has been introduced in many countries to control iodine deficiency. The two most commonly used approaches to assessing iodine nutrition on the population level are estimation of the household penetration of adequately iodized salt (HHIS) and measurement of urinary iodine concentrations (UICs). The aim of this review is to assess global and regional iodine status in 2012 by using each of these indicators. Recent findingsThe most recent national data on HHIS were obtained from UNICEF. The most recent data on UICs, primarily national data in school-age children, were obtained from a systematic literature search, the International Council for the Control of Iodine Deficiency Disorders and the WHO Micronutrients Database. The median UIC was used to classify national iodine status and the UIC distribution to estimate the number of individuals with low iodine intakes. Thirty-two countries are iodine deficient based on the national median UIC. Globally, 29.8% of school-age children (246 million) are estimated to have insufficient iodine intake. Out of 128 countries with HHIS data, 37 countries have salt iodization coverage that meets the international goal of at least 90% of households consuming adequately iodized salt and 39 countries have coverage rates of less than 50%. Overall, ≈70% of households worldwide have access to iodized salt. SummaryIodized salt programs need to be strengthened and extended to reach nearly one-third of the global population that still has inadequate iodine intakes.

The Swiss iodized salt program provides adequate iodine for school children and pregnant women, but weaning infants not receiving iodine-containing complementary foods as well as their mothers are iodine deficient.

BACKGROUND If children and pregnant women in the population are iodine sufficient, it is generally assumed infants are also sufficient. But weaning infants may be at risk of iodine deficiency because iodized salt contributes little dietary iodine during this period. To fill this gap, iodine fortification of infant formula milk (IFM) and complementary foods (CF) is likely important. OBJECTIVES The objective of the study was to first confirm that Swiss school children and pregnant women remain iodine sufficient and then to assess iodine status in infancy and the relative contribution of breast milk and IFM/CF to their iodine intakes. METHODS We measured urinary iodine concentrations (UIC) in national cross-sectional samples of: 1) pregnant women (n=648); 2) school children (n=916); 3) infants at three time points: at 3-4 d after birth and at 6 and 12 months (n=875); and 4) breast-feeding mothers (n=507). We measured breast milk iodine concentrations in the mothers, assessed iodine sources in infant diets, and analyzed iodine content of commercial IFM/CFs (n=22) and salt samples from the school childrens households (n=266). RESULTS Median (m) UICs in pregnant women (162 μg/liter) and school children (120 μg/liter) were sufficient, and 80% of the household salt was adequately iodized (≥15 ppm). However, mUICs in infants not receiving IFM/CF were not sufficient: 1) mUIC in breast-fed infants (82 μg/liter) was lower than in non-breast-fed infants (105 μg/liter) (P<0.001) and 2) mUIC in breast-fed weaning infants not receiving IFM/CF (70 μg/liter) was lower than infants receiving IFM (109 μg/liter) (P<0.01). mUIC was low in lactating mothers (67 μg/liter) and median breast milk iodine concentration was 49 μg/kg. CONCLUSIONS In countries in which iodized salt programs supply sufficient iodine to older children and pregnant women, weaning infants, particularly those not receiving iodine-containing IFM, may be at risk of inadequate iodine intakes.

Epidemiology of iodine deficiency: Salt iodisation and iodine status

Universal salt iodisation (USI) and iodine supplementation are highly effective strategies for preventing and controlling iodine deficiency. USI is now implemented in nearly all countries worldwide, and two-thirds of the worlds population is covered by iodised salt. The number of countries with iodine deficiency as a national public health problem has decreased from 110 in 1993 to 47 in 2007. Still one-third of households lack access to adequately iodised salt. Iodine deficiency remains a major threat to the health and development of populations around the world, particularly in children and pregnant women in low-income countries. Data on iodine status are available from 130 countries and approximately one-third of the global population is estimated to have a low iodine intake based on urinary iodine (UI) concentrations. Insufficient control of iodine fortification levels has led to excessive iodine intakes in 34 countries. The challenges ahead lie in ensuring higher coverage of adequately iodised salt, strengthening regular monitoring of salt iodisation and iodine status in the population, together with targeted interventions for vulnerable population groups.