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 world's 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.