|Food and Nutrition Bulletin Volume 17, Number 3, 1996 (UNU Food and Nutrition Bulletin, 1996, 104 pages)|
|Public health nutrition|
|Salt iodine variation within an extended Guatemalan community: The failure of intuitive assumptions|
The standard for countries with well-regulated and well-standardized commercial production of iodized salt is generally to have relatively homogeneous stocks, all with iodine content in accordance with their package label and within the specified and advertised limits. This would apply to industrialized nations such as the United States and Canada. Alternatively, without an attempt at iodine fortification, mined salt and even sea salt will have background iodine contents of 0 to 10 ppm. Variation in iodine content is a relatively recent phenomenon, uncovered with the advent of attempts to implement iodization of salt in developing countries with traditionally elevated prevalences of iodine-deficiency disorders. Uneven salt iodine concentrations were uncovered in surveys in the northern Indian Uttar Pradesh region , among 40 of the 44 districts in Kenya , and across the country of Guatemala .
A survey of 36 salt samples from different parts of Guatemala found a median iodine content of 7 ppm and a range of 0 to 64 ppm . There was a definite tendency towards more iodine in samples collected from cities and larger towns than in those from smaller and more rural sites, consistent with the trend reported around the world. Six packages of iodized salt of the same commercial brand from a supermarket chain in Guatemala City advertised concentrations within the range of 30 to 100 ppm . Hence, we hypothesized that salt purchased in the more urban setting (township) would have higher iodine content than that bought in rural hamlets, and that salt with a commercial identification on the package would be more likely to be iodized than salt of a no-name brand. However, our results do not support these hypotheses: we found no urban-rural difference in the municipality of San Pedro Sacatepequez and no difference in iodine content between samples labelled as iodized and those not so labelled.
As in our earlier study , the iodine contents in more than 60% of salt samples were below the mandated range; compared with the national sample, however, the median concentration in this specific district was three times higher (24 vs 7 ppm) but still below the minimum mandated level of 30 ppm. We can only speculate on the reasons for the less than adequate iodine levels in a majority of the salt samples from San Pedro Sacatepequez county and from throughout the country .
A number of factors are known to influence the stability of iodine in salt, such as the duration of storage, size of salt crystals, impurities, moisture of the salt, ambient temperature and humidity, and sunlight exposure. Iodate, which is used to fortify salt in Guatemala, is intrinsically more stable than the iodide used in industrialized nations. The presence of an inadequate amount of iodine in salt suggests an attempt to fortify the salt at the site of production. Inadequate quality control and lax government monitoring and enforcement probably play a role in the genesis of most samples in the range of 5 to 29 ppm. For samples with lower iodine levels, we cannot discount the introduction of unfortified salt into the supply either as contraband from a neighbouring country or from national producers not in compliance with the legal requirements to fortify their product.
In conclusion, the demonstration in recent years of a great variation and general inadequacy in the iodine concentrations of salt in the Guatemalan market [10, 11] was confirmed in this inquiry in a circumscribed region just outside the nation's capital. Within the county, no urban-rural difference was detected, and the presence or absence of a label of iodized salt provided no guidance as to the actual iodine content. The definitive control of iodine-deficiency disorders in this region and in Guatemala as a whole cannot be assured until an sufficient control of the quality of iodized salt is achieved.