What foods are naturally high in iodine? Iodine is a component of almost every living plant and animal. No standard measurements of iodine in food exist because iodine concentrations vary across the world. In general, foods from the sea contain the most iodine, followed by animal foods, then plant foods. Of all foods, seaweed (like kelp), is the most well known and reliable source of natural iodine. Egg and dairy products can also be good sources. Select Food Samples for Iodine Content.