Fucus vesiculosus, known by the common name Blader wrack, is a seaweed found on the coasts of the North Sea, the western Baltic Sea, and the Atlantic and Pacific Oceans, also known by the common names black tang, rockweed, bladder Fucus, sea oak, black tany, cut weed and rock wrack. It was the original source of iodine, discovered in 1811, and was used extensively to treat goitre, a swelling of the thyroid gland related to iodine deficiency. In the 1860s, it was claimed that bladder wrack, as a thyroid stimulant, could counter obesity by increasing the metabolic rate and, since then, it has been featured in numerous weight-loss remedies.