Iodized salt was introduced in the 1920’s to combat widespread goiter,specifically in the goiter belt (Great Lakes, Midwest, and intermountain regions of the U.S.). Salt fortification was called for after an experiment involving 5,000 Ohio schoolgirls using sodium iodide. The four year study showed an immediate decrease in goiter rate for those who previously had one, with no development of goiter in those who initially were goiter free. Half of the non-iodine controls developed goiter, proving the effectiveness of iodine supplementation in goiter prevention. In 1951, a follow-up study was completed in Michigan, showing that the introduction of iodized salt dropped the goiter rate from 38.6% to 1.4%. The resulting decrease in goiter rate and mental
retardation (cretinism) from salt iodization was a huge success, resulting in use of iodized salt around the world. 

Iodized salt is the most important source of iodine worldwide. It is commonly used in prophylaxis programs for the prevention of iodine deficiency. The iodine content of U.S. and Canadian iodized salt is 100 ppm, or 77 µg iodine/g sodium chloride, while it is generally 20-40 ppm in other countries. Iodized salt levels can vary by brand, and will decrease in concentration over time. It would take two grams (2,000 mg) of iodized salt in the U.S. to reach the daily recommended amount of iodine (150 µg) for non-pregnant adults. A majority of salt consumed in the U.S. comes from processed foods that do not typically use iodized salt. Unless meals are
prepared at home with branded iodized salt, the chance of supplying the body with enough iodine daily will significantly decrease. New dietary guidelines for Americans now recommend a decrease in salt consumption from 2.3 to 1.5 g/day, potentially resulting in a decrease in iodine intake and an increase in people
suffering from iodine deficiency.

Before you go buy iodized salt (the salt you have at home is most likely iodized – check the label), determine if
the foods you consume daily provide at least the daily recommended amount of iodine (see link below). Dairy and grain provide the highest levels of iodine in the U.S. diet with one glass of milk containing about 56 µg iodine (this can vary significantly). Frequent seafood consumption also helps in providing the body with iodine naturally. If you want to make sure you are getting at least 150 µg a day of iodine, you may want to supplement with a product containing at least that much (check your supplement labels, many contain iodine!) and work with your healthcare provider. Additionally, over 90% of dietary iodine is excreted in the urine, so a urine iodine test would help determine if you are getting enough daily iodine in your diet.

ZRT Laboratory offers two types of iodine tests. One in dried urine measuring iodine dietary intake, and the other, a Comprehensive Iodine/Thyroid test, correlating iodine measurement with a thyroid profile in dried bloods spot measuring fT3, fT4, TSH, TPO and Thyroglobulin.

Iodine contents of different foods: http://www.dietitians.ca/Nutrition-Resources-A-Z/Fact-Sheet-Pages(HTML)/Minerals/Food-Sources-of-Iodine.aspx

 

Sources:
Kimball OP. History of the Prevention of
Endemic Goiter. Bull World Hlth Org 1953;9:241-8.
Dunn JT. Guarding Our
Nation’s Thyroid Health. J Clin Endocrinol Metab 2002;87:489-99.

U.S.
Department of Agriculture and U.S. Department of Health and Human Services.
Dietary Guidelines for Americans, 2010. 7th Ed. Washington, DC: U.S.
Government Printing Office, 2010.

Pennington JT, Schoen SA, Salmon GD, et
al. Composition of Core Foods of the U.S. Food Supply, 1982–1991. J
Food Comp Anal 1995;8:171–217.

Nath SK, Moinier B, Thuiller F, Rongier M,
Desjeux JF. Urinary Excretion of Iodide and Fluoride from Supplemented Food
Grade Salt. Int J Vitam Nutr Res 1992;62:66-72.

Vought RL, London
WT. Iodine Intake, Excretion and Thyroidal Accumulation in Healthy
Subjects. J Clin Endocrinol Metab 1967;27:913-9.