For several decades, Europeans and North Americans harvested kelp for its iodine. The fronds were cut off exposed rocks at low tide, hence one popular name cut weed. Eventually, other iodine sources replaced kelp, and the harvesting ceased. Kelp is definitely high in iodine. Back in the days before iodized salt, when iodine deficiency was a real problem, kelp was a real blessing. But today, iodine deficiency is virtually unheard of in developed countries.  Kelp in particular is a good source of potassium, calcium, iodine, magnesium, and selenium. Kelp also contains an ingredient, Fucoidan.  Fucoidan is a sulfated polysaccharide found in the cell walls of many species of Brown seaweed. Fucoidans may support immune function, provide cardiovascular support, and may keep certain levels of inflammation within a healthy range. The iodine in Kelp promotes a healthy metabolism.