Scientific research indicates that organisms obtain iodine from nature, and the iodine concentration after enrichment is higher than that in the natural environment. Therefore, after enrichment, plants have higher iodine content than the soil; generally, animals contain more iodine than plants; and seafood has higher iodine content than land products.
The foods with the highest iodine content are seafood, such as kelp, laver, fresh hairtail, dried clams, dried scallops, dried mussels, sea cucumbers, jellyfish, lobster, etc. Among these, kelp has the highest iodine content, reaching over 240 mg/kg in dried kelp. Next are sea shellfish and fresh sea fish (around 800 μg/kg). Regular consumption of kelp not only supplements the body's iodine but also allows for the intake of other trace elements, amino acids, and vitamins.
Among land foods, eggs and dairy products have the highest iodine content (40 μg/kg to 90 μg/kg), followed by meat. Freshwater fish have lower iodine content than meat, and plants have the lowest iodine content, especially fruits and vegetables. Generally, most land plants have low iodine content, with an average of no more than 1.0 mg per kilogram. Only spinach and celery have higher iodine content, reaching 1.64 mg/kg and 1.60 mg/kg, respectively.