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Iodine Restrictions

Iodine Restrictions

When performing measurement of the thyroid iodine uptake rate or the radioiodine scintigraphy test, foods containing iodine must be restricted for one week before the tests.

As the thyroid iodine uptake rate measurement or radioiodine scintigraphy test may be performed when you receive your first examination, please restrict iodine intake before your first examination. Be aware, however, that these tests may not be necessary, depending on the examination results. For re-examination, iodine restrictions are necessary only when instructed by the doctor.

The test takes two days.
Moreover, as the test requires quite a lot of time, be sure to eat breakfast before coming to Kuma Hospital.

Foods that you cannot eat

While iodine is contained in various foods, seaweed tends to have the greatest effect on test results.
Please refrain from eating seaweed during the iodine restriction period.

A list of foods and food ingredients containing large amounts of iodine is shown below. Be careful to avoid ingesting these foods.

Foods containing large amounts of iodine

  • Konbu seaweed (konbu products such as grated yam konbu, tsukudani, konbu tea, etc.)
  • Wakame seaweed
  • Nori seaweed (nori tsukudani and other processed foods)
  • Hijiki and agar (mitsumame, tokoroten, etc.)
  • Iodine eggs

Flavor enhancers containing iodine

  • Konbu soup base
  • Flavorings available on the market (Some flavorings on the market contain konbu soup base or konbu extract. Example: Shimaya Dashinomoto, Ajinomoto hondashi, etc. Before use, always be sure to check the ingredients on the label. Soup bases using dried bonito, dried sardines, or dashijako are not a problem. Synthetic flavorings such as Ajinomoto, Haimi, or Inoichiban, etc., are also not a problem.)

Instant foods using the above flavorings containing iodine

Drugs containing iodine

  • Lugol, applied to the throat in ear, nose, and throat specialty
  • Isodine gargle and other mouthwashes
  • Dan-Rich (cold medicine), and other drugs using iodine

Precautions for eating at restaurants

As many Japanese dishes such as udon, sushi, donburi, or tsukemono pickles use konbu soup bases, their acceptability may be difficult to discern. When eating out at restaurants, avoidance of Japanese dishes is recommended.
Even Western-style dinner courses may have konbu soup base mixed into the miso soup or tsukemono pickles, and should be avoided.

List of dishes with low levels of iodine

  • Curry rice
  • Hayashi rice
  • Omelet rice
  • Fried rice
  • Hamburger steak
  • Croquettes
  • Pork cutlets
  • Sandwiches
  • Fried chicken
  • Mabodofu
  • Sweet and sour pork
  • Happosai
  • Gratin
  • Doria
  • Spaghetti (excluding Japan-style spaghetti)
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