Most of the kelp that people buy in the market is dried. Due to seawater pollution and other reasons, some commercially available kelp now contain a high arsenic content, and must be carefully treated before eating.
Arsenic and arsenic compounds are often toxic, and long-term over-intake can lead to chronic poisoning. The World Health Organization stipulates that the daily allowable intake of arsenic in the human body is 0.05 mg/kg body weight. The content of dried kelp arsenic that has just been processed has greatly exceeded the above standards. Experiments have proved that dried kelp is soaked in water for 5 to 10 hours, and the arsenic content in it is still as high as 5 mg/kg. After soaking in water for 24 hours, the arsenic content can meet the safety standards for consumption. When soaking, it is best to use weakly acidic water, such as taomi water or add a few drops of vinegar to tap water, so that the arsenic compound in kelp will react with the acid to become a soluble substance and dissolve in water.
Some people worry that kelp will be soaked for a long time and there will be a loss of nutrition. Indeed, after a long period of soaking, kelp loses some nutrients. Among them, vitamin B1 and niacin will lose a part, some trace elements and mannitol will lose more, and iodine will also have a certain loss. But these do not have much of an impact on the nutritional value of kelp. Iodine, in particular, is high in kelp and the loss of a small portion is irrelevant.
As we all know, patients with hyperthyroidism should not eat kelp, because the content of iodine in kelp is rich, which will aggravate the disease. In addition, pregnant women and nursing mothers should not eat more kelp. Because the iodine in kelp can enter the fetus and baby with the blood circulation, causing thyroid dysfunction.
Kelp is rich in iron, do not drink tea immediately after eating kelp (tea contains tannic acid), and do not immediately eat sour fruits (sour fruits contain vegetable acids). Because tannic acid and vegetable acids affect the absorption of iron.
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