iThei mdcdaelcinfd o c elllllrllll do thlsdtcfdbhfenMost guidelines now state that the doses at which adverse events to io-
dine occur may vary and that people with autoimmune thyroid disease
may experience adverse effects with iodine intakes considered safe for the
general population.
The dosage of iodine found in multivitamins and prenatal vitamins (150–
220 mcg) is not likely to be an issue for most people with Hashimoto’s. The
benefits of small doses of iodine likely outweigh the risks during pregnancy
and lactation, but I would caution against using higher doses of iodine.
Study participants who took as little as 400 mcg of iodine a day devel-
oped subclinical hypothyroidism.
Iodine intake seems to have a narrow therapeutic index. Some studies
even show having a slight deficiency is protective against developing
Hashimoto’s.
How Much Iodine Am I Getting?
While the average American may consume between 6 and 10 grams of
salt a day—largely due to processed foods—it is difficult to estimate the
amount of iodine contained in the Standard American Diet due to un-
certainty about whether the prepared food was made with iodized or
non-iodized salt.
The FDA estimates that between 2003 and 2004, the average iodine intake
in the United States ranged from 138 to 353 mcg. This data, however, does
not factor in the iodine people obtain from the use of iodized salt.
Proponents of high-dose iodine diets and regimens often cite that
Japan—a country with the highest iodine intake—averages 1,000–3,000
μg/day but has a lower incidence of chronic diseases. Yet incidence rates of
Hashimoto’s in Japan and the US are reported to be similar. Interestingly,
an association with one particular gene was found to contribute to the
development of Hashimoto’s in Japanese, but not in Caucasian, subjects.
So perhaps the Japanese are genetically better-adapted to high iodine in-
take than Caucasian populations are.
Test to Measure Iodine Status
More than 90 percent of dietary iodine is excreted in urine, thus dietary
iodine intake can be measured through a urinary iodine test. Spot urine
iodine measurements are a relatively easy tool to use. ZRT Lab (more infor-
mation in the Lab Test chapter) allows people in most states to order their
own spot urinary iodine tests.