Kelp is a large leafy brown algae that belongs to the algae family, and grows in the cold waters of the world's oceans.    Kelp is a good source of marine minerals such as potassium, magnesium, calcium and iron. As with most green foods, seaweed contains vitamins, cell salts and about 70 other minerals and trace elements, essential for good nutrition.    Kelp is particularly rich in iodine. Iodine promotes the production of thyroid hormones, which are required to maintain the metabolic rate. Iodine also helps in weight regulation and affects the rate of general metabolism.