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Dr. Tsubokura's Radiation Lecture Vol.28

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

55. Seaweed is rich in iodine

From a global standpoint, Japanese people consume a large amount of iodine from seafood.

Kombu, edible kelp, is especially rich in iodine compared to other seafood, such as seaweed, Hijiki, and laver. For example, one tablespoon (approx. 15 grams) of Tsukudani, simmered Kombu in soy sauce and mirin, contains 10 times more iodine than the recommended daily intake value for adults.

The amount of iodine contained in 500ml of sports drinks and instant noodles is about half of the recommended daily intake value, and blended teas contain more than sports drinks.

As you can see, kelp is used in many drinks, and many Japanese dishes contain iodine, such as miso soup with kelp and some simmered dishes.

Even if you consume too much iodine from a meal, most of it will be discharged in the urine. Therefore, there is no problem—the amount of iodine is adjusted to maintain the appropriate amount in the body. However, in the long term, excessive iodine intake could harm your health.

56. Iodine protects the thyroid

Japanese people tend to over-consume iodine by eating a large amount of seafood, such as kelp. Excessive amounts of iodine are mainly discharged in urine.

More than half of children in the Fukushima Prefecture had a high concentration of iodine in their urine, indicating that the children were consuming a high amount of iodine in everyday meals.

This fact also suggests that “an adequate (regular) amount of iodine occupied the thyroid at the time of the earthquake forward.” Furthermore, it means that “the radioactive iodine released after the nuclear accident did not have a space to enter in the thyroid. Therefore, a high daily intake of iodine worked as a protection against radiation exposure of the thyroid to radioactive iodine.”

Urine with an excessive amount of iodine does not indicate the increased radiation exposure of the thyroid by “radioactive iodine.”

Rather, this fact suggests the opposite.


The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on January 24th and 31st 2016 was reproduced for MRIC Global under the author's permission.

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