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Dr. Tsubokura's Radiation Lecture Vol.24

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

47. Sufficient amount of iodine from seafood

Thyroid glands produce thyroid hormones by using iodine, whose function is to strengthen metabolisms. Seafood—such as kelp, seaweed, and codfish—is a rich source of iodine. The fact that Japanese people consume much seafood in their everyday diets is well-known. Therefore, it has been suggested that Japanese people rarely develop iodine deficiencies, even if they do not have a special intention of maintaining their iodine levels.

After the 2011 Fukushima Daiichi nuclear accident, an irregular type of iodine spread into the environment. This iodine, which is called radioactive iodine, emits radiation and damages the thyroid gland.

The thyroid glands of people who eat seafood on a daily basis are filled with normal iodine. Thus, their thyroid glands have no room for absorbing radioactive iodine.

Japanese people’s custom of eating seafood is fortunate, as this custom protected them from thyroid exposure to radioactive iodine at the time of the accident.

By the way, the half-life of radioactive iodine is only 8 days, and this substance no longer exists in our daily environment.

48. Moderate progress of thyroid cancer

Thyroid glands produce thyroid hormones by using iodine, which strengthens metabolisms. Various kinds of thyroid-related disorders exist, and they are roughly classified into two categories: the category related to hormonal imbalances and the one related to the development of tumors. The diagnosis methods differ between the two categories of diseases. Typically, the former is diagnosed with blood samples, and the latter is diagnosed with physical examinations and ultrasonography.

Tumors are further classified as either benign or malignant. The occurrence of malignant tumors in the thyroid gland is called thyroid cancer. The incidence of one type of thyroid cancer, thyroid papilla carcinoma, reportedly increased among the residents who were affected by exposure to a large amount of radioactive iodine during the Chernobyl accident.

Generally speaking, thyroid cancers progress more slowly than the other types of cancers. It also reacts to treatment well and often has a good outcome, with a 20-year survival rate of 97% or more.


The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on November 29, December 6th 2015 and was reproduced for MRIC Global under the author's permission.

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