Iodine supplementation - Benefits outweigh risks

In 1990, iodine deficiency affected almost one-third of the world populatio n and was the greatest single cause of preventable brain damage and mental retardation. Following a resolution adopted by the World Summit for Childre n in 1990, major programmes of iodine supplementation were implemented by t he governments of the affected countries with the support of major donors. Iodisation of salt was recognised as the method of choice. Nine years later , by April 1999, 75% of the affected countries had legislation on salt iodi sation and 68% of the affected populations had access to iodised salt. The prevalence of iodine deficiency disorders decreased drastically in most cou ntries and the deficiency disappeared completely in some such as Peru. This result constitutes a public heath success unprecedented with a non-infecti ous disease. However, occasional adverse effects occurred. The principle effect is iodin e-induced hyperthyroidism which occurs essentially in older people with aut onomous nodular goitres, especially following iodine intake that is too rap id and of too massive an increment. The incidence of the disorder is usuall y low and reverts spontaneously to the background rate of hyperthyroidism o r even below this rate after 1 to 10 years of iodine supplementation. The p ossible occurrence of iodine-induced thyroiditis in susceptible individuals has not been clearly demonstrated by large epidemiological surveys. Iodine supplementation is followed by an increased prevalence of occult papillary carcinoma of the thyroid discovered at autopsy but the prognosis of thyroi d cancer is improved due to a shift towards differentiated forms of thyroid cancer that are diagnosed at earlier stages. Iodine-induced hyperthyroidism and other adverse effects can be almost enti rely avoided by adequate and sustained quality control and monitoring of io dine supplementation which should also confirm adequate iodine intake. Available evidence clearly confirms that the benefits of correcting iodine deficiency far outweigh the risks of iodine supplementation.