After the hydrogen explosion accident at the Fukushima nuclear power plant in Japan, not only the local people in Japan, but also the public in our country showed great concern about the possible nuclear leakage that might endanger the coastal areas of our country. Especially, many people learned that the Japanese authorities were distributing "iodine tablets" to residents around the nuclear power plant. Some coastal areas in our country even saw a rush to buy iodine tablets, leading to their sell-out in pharmacies. There were even stock market speculators who turned their attention to listed companies producing "iodine tablets". So, why is it said that "iodine tablets" can resist nuclear radiation? Is it necessary for residents in the coastal areas of our country to take them? What adverse consequences will inappropriate intake bring? Let us understand the various relationships between iodine, human body, and radiation.
What is the use of iodine for the human body?
Iodine is an essential element for the human body. We have known since we were young that we need to consume iodized salt, otherwise we would get "big neck disease". The most important function of iodine in the human body is as a raw material for synthesizing thyroid hormones. As the name suggests, thyroid hormone is a hormone secreted by the thyroid gland, which is an important hormone for maintaining human development, growth, and promoting material metabolism. Without it, some very serious problems will occur. For example, if this hormone is lacking from childhood, the growth and development of bones, nervous system, etc. will be affected, causing children to be short in stature and intellectually disabled. Clinically, it is called "cretinism". In addition, there are some diseases such as myxedema and simple goiter, all of which are related to it.
As for the "big neck disease" that was prevalent in some regions in the past, clinically called "endemic goiter", it is usually due to iodine deficiency, making the body's iodine intake insufficient. Therefore, thyroid cells will continue to compensate and proliferate - because the body mistakenly thinks that there are not enough thyroid cells, which leads to insufficient hormone synthesis, and finally the neck becomes enlarged.
Will being full of "iodine" protect against nuclear radiation?
So, many people may wonder, what is the relationship between iodine and radiation? Can iodine really protect against radiation?
In the waste of nuclear reactors, and of course including the radioactive substances leaked in nuclear accidents, there is a large amount of a radioactive element called "iodine-131". This is a radioactive isotope of iodine, which releases β and γ rays during decay. It belongs to a highly toxic nuclide and is often used in medicine for its radioactivity to treat thyroid diseases. The "iodine tablets" possibly distributed in this event in Japan are preventive protective measures against the radiation of iodine-131.
As mentioned earlier, the thyroid in the human body needs to absorb iodine elements to complete the synthesis of thyroid hormones. The specific synthesis mechanism we will not elaborate on today. Just understand that these iodine elements will eventually enter the thyroid tissue. Therefore, if these radioactive iodine-131 elements are absorbed by the thyroid, they will continuously radiate and damage the thyroid tissue, and even other organs and tissues in the human body. Since this radiation occurs inside the body, it is called "internal irradiation". When we ingest a certain dose of iodine, making the thyroid reach a "saturated state" for iodine absorption, it will no longer absorb those radioactive iodine elements, which is equivalent to "resisting" nuclear radiation.
However, in the nuclear waste leaked from the reactor, besides iodine-131, there are also a large number of radioactive substances with long half-lives, such as cesium-137, and some second-class radioactive substances with short half-lives. Taking iodine tablets has no effect on these types of nuclear radiation.
What are the adverse effects of excessive iodine intake?
After this public crisis event occurred, especially as the media's reporting on the event "deepened", it made people in the coastal areas of our country also start worrying about their own safety. There were even reports claiming that Finland had already started hoarding medicinal iodine agents. So, is it necessary for the coastal areas of our country to take iodine agents to prevent radiation hazards? What are the adverse consequences of taking iodine casually?
Many people would say that we are consuming iodine every day, and there is iodine in salt and seafood. Our parents have always warned us to eat more iodine, which is good for health. Indeed, the normal human body can excrete over-consumed iodine within a certain degree through normal channels, generally without serious consequences. Usually, the daily iodine requirement for normal adults, which is also the recommended daily iodine intake by the World Health Organization, is 150-300 micrograms. The average iodine content in iodized salt in our country is 30mg/kg, meaning that if we consume 5-10 grams of salt per day, the daily iodine intake is just in line with the recommended requirements.
However, inappropriate iodine intake can lead to hyperthyroidism or autoimmune thyroiditis and other diseases. And in most areas of our country, the food iodine intake itself is not low, especially in coastal areas rich in seafood. Adding iodine intake from iodized salt may be one of the reasons for the increased incidence of thyroid diseases. Last year, the Ministry of Health also released the "Risk Assessment of Iodized Salt and Residents' Iodine Nutrition Status in China." It is visible that too much iodine can also cause problems.
Is it necessary for residents in the coastal areas of our country to take iodine to prevent nuclear radiation at this stage?
As mentioned above, on the one hand, it may turn latent autoimmune thyroid diseases into manifest ones, or increase the risk of hyperthyroidism; and on the other hand, taking iodine can only solve the internal radiation problem caused by iodine-131. Regarding the latter, iodine-131 is a radioactive element with a relatively short half-life, only 8.0197 days. That is to say, after about a few weeks, the content of radioactive iodine-131 will be negligible.