As a result of collaborative efforts with international organizations and the salt industry, many developing and developed countries practice universal salt iodization (USI) or have mandatory salt fortification programs. As a consequence, the prevalence of iodine deficiency decreased dramatically. The United States and Canada are among the few developed countries that do not practice USI. Such an undertaking would require evidence of deficiency among vulnerable population groups, including pregnant women, newborns, and developing infants. Government agencies in the United States rely heavily on data from NHANES to assess the iodine status of the general population and pregnant women in particular. NHANES data suggest that pregnant women in the United States remain mildly deficient. This is important, because the developing fetus is dependent on maternal iodine intake for normal brain development throughout pregnancy. Professional societies have recommended that pregnant and lactating women, or those considering pregnancy, consume a supplement providing 150 µg iodine daily. The United States and Canada collaborate on the daily recommended intake and are also confronted with the challenge of identifying the studies needed to determine if USI is likely to be beneficial to vulnerable population groups without exposing them to harm.
The role of enhanced thyroid-stimulating hormone (TSH) secretion, in the aetiology of thyroid cancer is not totally consistent. Circumstances and conditions which cause (e.g., iodine deficiency, through suboptimal intake in water and food) or indicate (e.g., goitre) increased TSH secretion have been associated to increased risk of thyroid cancer, most notably follicular and anaplastic carcinomas. Elevated incidence and mortality rates of thyroid cancer, however, are also found in areas were iodine intake is high (Hawaii, Iceland). At least in some countries (Switzerland), a favourable impact of the introduction of iodized salt on mortality from thyroid cancer has been reported. Elsewhere, the correction of iodine deficiency has coincided with elevations of diagnostic standards (e.g., spread of thyroid scintigraphy, ultrasound, and fine-needle biopsy) and corresponding increases in incidence of papillary carcinomas, often clinically silent, thus hampering a distinction of the two phenomena. Upward trends of papillary carcinoma incidence have, however, been seen in most affluent countries, irrespective of the iodine status of the population.
The Interregional center of public health and development assisted by Sechenov Moscow Medical Academy undertook, 1999-2000, a study of the standard of knowledge, attitude and conduct of consumers in respect to the use of iodinated salt (IS) in the prevention of iodine-deficient diseases (IDD). It was demonstrated that, on the average per one district, 19% of city respondents and 13% of rural respondents used IS only. About 31% of city respondents used IS when it was available at the next-door shop, i.e. from time to time. This figure reached 48% in Irkutsk and Orenburg Regions. The share of those who used IS sometimes in rural regions made an average of 20.7%. 67.2% of those who believe that IDD can be prevented think that ID can also be prevented. Less than 5% of them say ID cannot be regarded as a reliable tool in the prevention of IDD.