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Food · Vegetables · Sea Vegetables
food source · 1
Kelp concentrates iodine from seawater to very high levels, and one serving can far exceed a day's need. It is a source of iodine and also one whose portion needs limiting: too much iodine disrupts the thyroid just as too little does.
Mechanism · Seaweed concentrates iodine
Iodine is dissolved in seawater, and large brown seaweeds such as kelp build it up in their tissues to a level almost unmatched among natural foods. The thyroid regulates how much iodine it takes in, but a large excess over a long time can still disrupt hormone production.
Safety · Use a little, and ask your doctor first
A pinch of dried kelp or a bowl of kelp soup can hold tens to hundreds of times the US adult recommended intake of 150 µg, and it is common for a single serving of commercial kelp or seaweed supplements to exceed the tolerable upper intake level, so kelp is best used in small amounts, for example to make stock. People with thyroid disease or who take thyroid medication should ask their doctor before eating a lot of kelp or taking seaweed supplements.