In recent years, the debate over "too much iodine" and "too little iodine" has never ceased. Why does such a tiny element like iodine spark such a controversy?
The Main Functions of Iodine
Iodine is an essential nutrient for the human body. It was first isolated from seaweed ash in 1813 by a French scholar and was later named Iodine. The total amount of iodine in the human body is about 20 to 50 milligrams, and it is mainly distributed in the thyroid gland. The thyroid gland is located at the Adam's apple, on both sides of the ring-shaped cartilage just below it. Under normal circumstances, the thyroid gland is not visible or palpable in the neck.
Iodine in the body is mainly used to synthesize thyroid hormones; therefore, its physiological effects are achieved through these hormones. Thyroid hormones play an important role in the human body's growth, development, and metabolism. They can promote the synthesis and decomposition of proteins, fats, and carbohydrates; participate in maintaining and regulating body temperature, and keeping normal metabolism and vital activities; promote metabolic and physical growth and development. If children lack iodine, their growth and development can be hindered. They promote the development and differentiation of the nervous system, which is especially important for a fetus and infants. If a fetus or infant lacks iodine, it will directly impair intellectual development. In addition, iodine can also promote the absorption and utilization of vitamins in food, activate many important enzymes, and promote material metabolism.
The Main Functions of Iodine
Our understanding of iodine began with iodine deficiency disorders. The iodine we need mainly comes from food and drinking water, and the iodine content in these is related to the geographical environment where plants grow or animals graze. If the soil lacks iodine, the plants will also be deficient in iodine, and the iodine intake of animals will be insufficient. As people mainly consume local water, plants, and animals, this can lead to insufficient iodine intake. Generally, coastal areas have the highest iodine content in soil, followed by plains, while mountainous areas are often iodine-deficient regions.
Since iodine is involved in various physiological processes in the body, such as metabolism, having too little iodine is not an option. For adults, the initial clinical symptom of iodine deficiency is an enlarged thyroid gland. This is because when iodine is deficient, thyroid cells proliferate to gather as much iodine as possible, forming a visible lump in the neck called a goiter, commonly known as a "struma." Nowadays, it is rare to see people with a "struma," but I remember seeing some elderly people with a large one in their necks when I was a child.
During pregnancy, iodine deficiency can affect fetal development. Severe iodine deficiency can lead to miscarriage, stillbirth, premature birth, and congenital malformations, with the most severe harm being to the fetal nervous system. If children in their developmental stage lack iodine, it can lead to poor physical and nervous system development, manifesting as intellectual disabilities, deaf-mutism, short stature, etc. In severe cases, it is clinically known as "cretinism."
If too little iodine is not good, then is too much iodine better? The answer is also no. Long-term excessive iodine intake may cause high-iodine goiter. In some high-iodine areas, long-term intake of high doses of iodine can lead to iodine-induced hyperthyroidism.
How Much Iodine is Needed Daily
The recommended daily iodine intake for each person is: 50 micrograms for children under 3 years old, 90 micrograms for ages 4-10, 120 micrograms for ages 11-13, and 150 micrograms for ages 14 and above. Pregnant and lactating women need not only to meet their own body's needs but also to support the development of the fetus or the needs of the infant, so their requirement is about 200 micrograms higher than that of the average adult.
The foods richest in iodine are primarily seafood, such as kelp, seaweed, algae, and marine fish. Besides seafood, animal foods have a higher iodine content than plant-based foods, with grains, vegetables, and fruits having the lowest iodine content. If your body lacks iodine, you can appropriately eat more seafood. Conversely, you should eat less. Additionally, iodine is also added to salt, but the iodine in salt is unstable. Light exposure, air oxidation, and heating can deactivate the iodine. For example, when frying or stir-frying at high temperatures, the loss rate of iodine in salt can reach 25% to 67%. Therefore, to preserve the iodine content in salt, it is best to store it in an airtight container in a place away from light. Of course, if you want to reduce your iodine intake, you can do the opposite to deactivate it.
In conclusion, the key to nutrition lies in balance and moderation. Not only should iodine intake be appropriate, but the same applies to other nutrients. More is not always better when it comes to nutrition; only moderation is the healthiest.
Seafood is very rich in iodine
This article is excerpted from "Dr. Ma Talks About Nutrition" by Guansheng Ma, authorized by Phoenix Hanzhang Books. Reproduction is strictly prohibited.