In 2008, the 22nd Australian Total Diet Study produced by the Food Standards Australia New Zealand at food standards.gov.au, confirmed that nearly 50% of Australians, once an iodine-sufficient population, had inadequate iodine intakes. Now, it seems the Unites States may be facing the same future. Research shows iodized salt, as an iodine source, is highly variable and may fall short of the recommended levels. This could lead to an increase in iodine deficiency disorders.
United States Iodized Salt Low in Iodine
In a study by Purnendu K. Dasgupta et al, “Iodine Nutrition: Iodine Content of Iodized Salt in the United States”, published in the 2008 Environmental Science & Technology journal, Volume 42, issue 4, samples of iodized table salt from freshly opened containers were analysed for their iodine source. The results revealed 47 of the 88 samples (53%) fell below the United States Food and Drug Administration’s (USFDA) recommended iodine content. Six containers exceeded the recommended levels.
Additionally, the study revealed inconsistencies within salt containers. Several samples from individual salt containers, at differing depths, showed uniformity in some containers with great variations in iodine content of others.
Iodine Intake Decreasing
According to Purnendu K. Dasgupta et al, the iodine intake in the United States, like Australia, has been decreasing over the last decade. Iodized salt is the main source of iodine in the United States. The United States introduced iodized salt in 1924; however, it has never been mandatory for fears by some parties of “medication by legislation”.
The reasons behind the decrease in iodine intake include:
- Health concerns with high salt, for example, hypertension
- Removal of iodine from breads
- Reduced use of iodine-based disinfectants in milk production
- Reduced use of iodine in animal feed
- Variability and possibly low levels of iodine in iodized salt
- Replacement of table salt for sea salt, which has a low iodine content (64mcg per kilogram)
- Reduced consumption of cow’s milk.
Additionally, Jason V. Dyke, one of the researchers in the Purnendu K. Dasgupta et al study, states on his research profile for the Dasgupta Research Group, approximately 70% of food grade United States salt is not iodized.
Iodine Facts in the United States
The National Health and Nutrition Surveys (NHANES) have monitored urine iodine levels over the last 33 years. Median urinary iodine concentration (UIC) levels tests the body’s iodine status. In children and adults, levels below 100mcg/L indicate iodine deficiency, in pregnant women the iodine deficiency stage is below 150mcg/L. The following shows the median urinary iodine concentration levels from each of the NHANES surveys in adults and reproductive women.
Adults:
1971-1974 median UIC = 320mcg/L
1988-1994 median UIC= 145mcg/L
2001-2002 median UIC= 165mcg/L
2003-2004 median UIC= 160mcg/L.
Women in reproductive years:
2001-2002 36% of reproductive women were below 100mcg/L; 15% were below 50mcg/L
2003-2004 median UIC= 136mcg/L; however, 15% were below 50mcg/L.
These iodine facts show median urinary iodine concentrations in adults have fallen since 1974 but stabilised over the 2001 to 2004 periods. However, in reproductive women deficiencies were prevalent, falling below the level of deficiency of adults of 100mcg/L and 150mcg/L for pregnant women.
Fetal Development Affected the Greatest by Iodine Deficiency
Women of reproductive years and infants are the most vulnerable to iodine deficiency. Iodine is crucial for nervous system development in fetal development and infants. In the 2007 publication “Assessment of Iodine Deficiency Disorders and Monitoring their Elimination” the World Health Organisation (WHO) the United Nations Children's Fund (UNICEF), the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) states, “On a worldwide basis, iodine deficiency is the single most preventable cause of brain damage.”
Iodine deficiency has also been linked with attention deficient disorder (ADD). The link between ADD and iodine and the fact that approximately 2 million children in the United States have ADD prompted the study by Purnendu K. Dasgupta et al. They wanted to check that the production of iodized salt was being properly carried out. They concluded in their study “The ultimate question for future generations pondering the too much vs too little iodine dilemma may be simple: if we have a right to have children, do children have a right to be born with their full potential?”
References:
Dasgupta, P. K., Liu, Y., & Dyke, J. V. (2008). Iodine nutrition: iodine content of iodized salt in the United States. Environ Sci Technol, 42(4), 1315-1323.
Patrick, L. (2008). Iodine: deficiency and therapeutic considerations. Altern Med Rev, 13(2), 116-127.
Caldwell, K. L., Miller, G. A., Wang, R. Y., Jain, R. B., & Jones, R. L. (2008). Iodine status of the U.S. population, National Health and Nutrition Examination Survey 2003-2004. Thyroid, 18(11), 1207-1214.
Melissa Peterson - Melissa Peterson is a naturopath specializing in nutrition education. Melissa has been writing and editing technical and patient-friendly ...
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