Last updated Dec 18, 2010
How much Iodine do we really need?
Due to new rearch results, this article is being rewritten.
In brief, a study has found a fundamental error in the Iodine Loading test methodology of Abrahms used for assessing whole body sufficiency of Iodine.
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The test assumes that there is a Iodine deficiency if a person has excreted less than 90% of the Iodine within 24 hrs after ingesting a test dose of 50mg of Iodine.
A recent study found that within 24 hours, healthy persons excreted at an average 70.4% of the ingested Iodine. Even after 3x24 hours, 90% excretion had not been quite achieved (it was 86.2% at an average). See image below where the peak is the amount excreted after 24 hrs and still 24 hrs later there was a significant amount in the urine (13.1 %).
This means that the test of Abrahams, although technically refined and precise, yields a considerable overestimation of Iodine deficiency because of the wrong assumption that always at least 90% of the test load of 50 mg Iodine is excreted within 24 hours. Considering that still after 72hrs no one of the research subjects had achieved 90% excretion, it is obvious that a very different limit needs to be set, perhaps 70% or less during the first 24hrs (larger numbers of subjects are required to establish a reference valuse).
Consequently, the opinion of Abrahms, that Iodine deficiency is endemic in the population needs to be revised. It may still be common, especially in inland and montaneous areas, but this study indicates that the extent of deficiency may be less than Abrahams found, perhaps to a considerable extent.
Also the conclusion of Abrahms that we need about 12 mg daily for preventing deficiency is no more valid. The Japanese intake, through traditional food, is of this order of magnitude, but it does not prove that Iodine is the reason for the high life expectancy especially among people eating this food. The amount of seaweed that yields 12 mg per day, may be the amount required for providing some other important substance, and therr are several health promoting substances in seaweed.
My conclusion is that the recommendations of Abrahams need to be revised. The first step would be for Abraham to recalculate his test results using perhaps 70% excretion as the 24hr level. A new round with his technically excellent test method needs to be made in order to establish what dose of Iodine is required for sustaining sufficiency.
Source: Theodore Zava. "Evaluation of the Iodine Loading Test: Urine Iodine Excretion Kinetics after Consumption of 50 mg Iodine/Iodide."; Townsend letter; Jan 2013.