Fundamentación del sistema de actividades

Correcting iodine deficiency has been a long term commitment of the World Health Organization, with the goal of eliminating iodine deficiency by 2000 set in the 1990 World Summit for Children2. Iodine repletion in the general population is such that

the median urinary iodine concentration is higher than 100 μg/L, with no more than 20% of the population being below 50 μg/L.

Diverse vehicles for iodine supplementations are available, including water, milk, dairy products, flour, oil, salt, etc. Iodination of water can be an effective way to increase iodine levels in humans, crops and animals. Iodised irrigation water has been successful in reducing iodine deficiency in China (111). Similarly, fortified animal feeds can also raise the iodine concentration in animal products. Accordingly daily iodine supplementation can be obtained through food products like bread, milk and infant formula (112). Another approach is to add iodine into foods, such as flour. However, little research has been conducted and the effect of this approach is still unclear. Further assessments are needed, particularly on the iodisation technology,

2_{In 2002, the target was later extended to 2005 at the Special Session on Children of the United}

optimal iodine fortification levels and its potential coverage. Iodised oil is usually distributed in populations in remote areas where other iodine supplementation vehicles are difficult to reach. It is prepared by adding iodine to seed or vegetable oil. It contains about 40% organically combined iodine. Iodised oil can be administered orally or given by intramuscular injection once or twice a year (113;114).

Compared to the previous vehicles, salt is the major vehicle for iodine supplementation worldwide. It is mainly because of the following advantages (32;57):

 Salt is commonly and stably consumed by people throughout the year;

 Salt production is limited to a few geographical areas;

 The quality of iodised salt is easily monitored;

 The addition of iodine to salt does not affect its taste, odour and colour;

 Salt iodisation programmes are easy to implement.

Salt iodisation is the most cost-effective way to improve the population iodine intake. It costs only US$0.02-0.09 per person per year to obtain sufficient iodine. The implementation of salt iodisation in children can avert $1,000 per child death and save $34-36 per disability-adjusted life years (DALYs) (115).

Universal salt iodisation (USI) was adopted in the 54th World Health Assembly in 1994 to promote the use of iodised salt in the general population and eliminate IDD in the world. The WHO, United Nations Children's Fund (UNICEF) and International Council for Control of Iodine Deficiency Disorders (ICCIDD) have been recommending salt iodisation as the primary strategy for controlling iodine

deficiency since then. USI requires all food grade salt be iodised. Several countries in Europe and North America, such as Sweden, Austria and the United States, add potassium iodide (KIO3) to salt. Other countries usually add potassium iodate (KI)

because it is more stable and less soluble than KIO3, especially in hot and humid

conditions (e.g. tropical regions). Assuming average daily salt intake of 10 grams per capita and 40% iodine loss from salt during delivery and cooking (107), the salt industry is advised to add 20-40 mg iodine in each kg of salt during production.

Therefore individuals can consume 150 μg/day iodine, as recommended by the

WHO.

To achieve the goal of sustainable elimination of IDD, two indicators are used: 1) at

least 90% of households should be covered by adequately iodised salt (≥15 ppm); and 2) median UI should be 100-199 μg/L in the general population and 150-249 μg/L in pregnant women (107).

Remarkable achievements have been obtained since the introduction of USI worldwide. More than 170 countries have adopted the USI programme for controlling iodine deficiency by 1998 (116). Of the 130 countries affected by IDD, 110 have established legislations on salt iodisation (117). The overall coverage of iodised salt is steadily improving: an estimated 69% of households worldwide are using iodised salt, compared to less than 20% in 1990s (23), although populations in Central Eastern Europe, Commonwealth of Independent States and South Asia have much lower coverage of iodised salt. The number of countries at risk of iodine deficiency reduced from 110 in 1993 to 47 in 2007 (118), and further down to 32 in

2011 (17). Over 90 million newborns every year are now protected from learning disabilities caused by IDD.

Figure 2.3 Iodine status based on national median UIC data

Note: Reprinted from Andersson et al. (17) with permission.

However, the progress of the USI programme differs from one region to another. Wide geographical variations are observed in the availability and consumption of iodised salt (119) in different parts of the world. For instance, East Asia has an 86% coverage of iodised salt, whereas 49% South Asian households are still not protected by iodised salt. More disparities are found from country to country (90). In South Asia, Sri Lanka and Bhutan have met the USI 90% target line, while the coverage in Pakistan and Afghanistan is less than 30% (119). In Africa, the goitre prevalence rate dropped considerably after introduction of iodised salt: 20%, 60%, 50% and 38% reduction in goitre rates were achieved in Kenya, Cameroon, Zambia and Zimbabwe respectively (120). In Lesotho, iodine deficiency is no longer a public health problem after legislation on USI was established in 2000 (121). Access to iodised salt can

vary even within a country. For example, with 30% households covered by iodised salt in Russia, the coverage in 7 out of 17 surveyed regions is lower than 10% (122).

Additionally, there are diverse geographical patterns of iodine status at national and sub-national level. In Sub-Saharan Africa, several countries (e.g. Chad and the Central African Republic) are severely iodine deficient, whereas their neighbouring countries, such as Nigeria and the Democratic Republic of Congo, are at risk of IIH (Figure 2.3). Valeixet al.(123) reveal a west-east pattern with regard to median UIC concentration in France. In a study in Albania, significant geographical variations of

median UIC (3.52-1,079 μg/L) are found among four regions (124). In Russia, while

iodine deficiency has been reduced in certain Russian regions (e.g. Moscow and Tartarstan) in accordance with increased urinary iodine concentration, it remains unchanged in others (122).