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Effectiveness of salt iodization for the prevention of iodine-deficiency disorders
References
Two papers in this issue, “Virtual elimination of iodine-deficiency disorders achieved in nine counties of Jiangsu Province, China” [1] and “Knowledge, attitudes, and practices of people in Ulaanbaatar, Mongolia, with regard to iodine-deficiency disorders and iodized salt” [2], report contemporary success in the introduction of a programme of iodized salt in a developing country. The latter of these depended on an education campaign and achieved a substantial consumption of this salt, despite its slightly higher price. The study demonstrated that where policy makers decide that a campaign for the iodization of salt in endemic areas must be based on achieving sufficient voluntary consumption, it can be effective. Unfortunately, it was accompanied by an increase in total salt consumption by 58% of the families, because they thought more salt would be good for them. Although most individuals are not affected by salt intake at moderate levels, some have a rise in blood pressure [3]. The higher the sodium intake, the higher is the prevalence of essential hypertension in a population, with an associated increase in morbidity and mortality from cardiovascular diseases.
It is only fair to point out, therefore, that where acceptable, there is a cheaper and better alternative. This is legislation requiring the iodization of all salt for human consumption in a country or region. It can be highly effective if compliance with the legislation is ensured by careful laboratory monitoring and enforcement For example, after legislation requiring the iodization of all salt for human consumption was implemented and monitored in Guatemala, the nationwide prevalence of endemic goitre fell from 38% in 1962 to 14% in 1965 [4], and two years later it was 5%. No investment in a nationwide education campaign was required, and there was no effect on salt consumption.
Countries that have followed the legislative approach of making salt iodization obligatory have been successful wherever they have implemented it. Those countries that have relied on the promotion of voluntary consumption of iodized salt have spent much more money and rarely achieved comparable results. Nevertheless, this paper is of value for those countries where, for policy or political reasons, a public information campaign is required to promote either voluntary use of iodized salt or the acceptability of legislation for compulsory iodization. However, the other paper demonstrates once again that if iodization of all or most salt for human consumption is achieved, goitre promptly disappears as a public health problem [1]. This is the basis for the increasingly successful global programme for the elimination of iodine-deficiency disorders of UNICEF/World Health Organization/International Council for the Control of Iodine-Deficiency Disorders [5]. The feasibility and effectiveness of iodization of even crude moist salt was conclusively demonstrated by the Institution of Nutrition of Central America and Panama (INCAP) in the early 1960s, as indicated above. In the intervening years, new data have established the lasting effect of iodine deficiency in pregnancy on the cognitive performance of offspring [6]. It is a tragic irony that almost 40 years later the Bulletin finds it useful to publish a paper that confirms the effectiveness of the iodization of salt for a new generation.
Nevin S. Scrimshaw
1. Zhao J, Wang H, Ge J, Zhang Q, Huan X, Shang L, Pan R, van der Haar F. Virtual elimination of iodine-deficiency disorders achieved in nine counties of Jiangsu Province, China. Food Nutr Bull 1998;19:347-353.
2. Yamada C, Oyunchimeg D, Igari T, Buttumur D, Oyunbileg M, Umenai T. A study of knowledge, attitudes, and practice of people on iodine deficiency disorders and iodized salt in Ulaanbaatar, Mongolia. Food Nutr Bull 1998;19(4):354-359.
3. Dahl LK, Heine M, Tassinari L. Effects of chronic excess salt ingestion: evidence that genetic factors play an important role in susceptibility to experimental hypertension. J Exp Med 1962; 115:1173-90.
4. de Leon JR, Retana OG. La erradicación del bocio endemico en Guatemala: informe final. Nutr Bromotol Toxico 1966;5:43-51.
5. UNICEF. The state of the world’s children, 1998. Oxford: Oxford University Press, 1998.
6. Stanbury JB, ed. The damaged brain of iodine deficiency. Elmsford, NY, USA: Cognitive Communications, 1994.
