Which vegetables contain iodine?
Among foods, seafood has the highest iodine content, with kelp, jellyfish, seaweed,苔条 (a type of seaweed), and mussels being particularly rich.
Traditional Chinese medicine ingredients such as seaweed, kelp, and Rhizoma Dioscoreae Bulbiferae should be strictly avoided.
Generally speaking, most terrestrial plants have low iodine content, averaging no more than 1.0 mg per kilogram. However, spinach and celery have higher iodine levels, reaching 1.64 mg and 1.60 mg per kilogram, respectively.
The iodine content in seafood is several times that of terrestrial plants, in some cases as high as tens of times. Typically, the kelp we eat has an iodine content of 10.0 mg per kilogram.
Sea fish and seaweed are also good sources of iodine in daily life. Regular consumption of kelp not only replenishes the body's iodine but also allows for the intake of other trace elements, amino acids, and vitamins. Therefore, only seafood is a food naturally high in iodine. You should pay attention to eating more of it, as it is the best natural source of iodine supplementation.
Nowadays, some mineral waters also contain iodine, so be mindful when drinking them. Also, do not eat iodized salt!
Seawater is the most abundant and stable source of iodine, with an iodine concentration of 50-60 micrograms per liter, earning it the name "iodine reservoir." Due to evaporation, some of the iodine in seawater enters the atmosphere. This results in about 400,000 tons of iodine entering the atmosphere annually, which then falls back to land in the form of rain or snow. This is the cycle of iodine in nature.
The iodine content in volcanic rock soil can be as high as 9.0 mg per kilogram. Soil in areas with steep terrain, inland areas, and areas formed by glacial runoff has low iodine content, while soil in coastal areas and islands has high iodine content.
Organisms obtain iodine from nature, and after concentration, the iodine level is higher than that in the natural environment. Therefore, after concentration, plants have a higher iodine content than soil; animals have higher iodine content than plants; and seafood has higher iodine content than terrestrial products.
Marine organisms have a very high iodine content. The foods with the highest iodine content are seafood, such as kelp, seaweed, fresh hairtail, dried clams, dried scallops, mussels, sea cucumbers, jellyfish, and lobster. Kelp has the highest iodine content, exceeding 240 mg per kilogram in dried kelp. Next are sea shellfish and fresh sea fish (around 800 micrograms per kilogram). However, the iodine content in salt is extremely minimal; the more refined the salt, the less iodine it contains. The iodine content in sea salt is about 20 micrograms per kilogram. If a person consumes 10 grams of salt per day, they can only obtain 2 micrograms of iodine, which is far from meeting the needs to prevent iodine deficiency disorders.
Among terrestrial foods, eggs and milk have the highest iodine content (40-90 micrograms per kilogram), followed by meat. The iodine content in freshwater fish is lower than that in meat, and plants have the lowest iodine content, especially fruits and vegetables.
80%-90% of the iodine in the human body comes from food, 10%-20% is obtained through drinking water, and 5% comes from the air. Therefore, iodine in food is the main source of iodine for the human body. Iodides in food must be reduced to iodide ions before they can be absorbed; iodine bound to amino acids can be directly absorbed. Calcium, fluorine, and magnesium in the gastrointestinal tract hinder iodine absorption, which is particularly significant in conditions of iodine deficiency. Insufficient protein and calories in the body can also hinder the gastrointestinal absorption of iodine. The respiratory tract and skin can also absorb small amounts of iodine.
The physiological role of iodine in the human body is achieved through the synthesis of thyroid hormones. Thyroid hormone is one of the most important hormones in the body, and its main physiological functions are:
(1) Maintaining the body's energy metabolism (breaking down substances to provide energy for life activities) and heat production (maintaining body temperature). A reduction in thyroid hormone synthesis caused by iodine deficiency leads to impaired basic life functions and decreased physical energy, and this effect is lifelong.
(2) Promoting physical development. Thyroid hormone regulates bone development, sexual development, muscle development, and height and weight in children during their growth period. A deficiency in thyroid hormone can lead to symptoms and signs of developmental retardation, such as stunted physical development, delayed sexual development, short stature, and weak muscles.
(3) Brain development. During a certain period of fetal or infant brain development, the brain must rely on thyroid hormones. A deficiency can lead to varying degrees of brain developmental retardation, resulting in varying degrees of intellectual disability after birth. This disability is largely irreversible, and supplementing iodine after this critical period is of no help. However, iodine supplementation can still ensure normal physical development, correct hypothyroidism, restore physical energy, and indirectly improve mental function.