The medicinal virtues of kelp are primarily related to its content of viscous fiber called algin. Algin is responsible for the use of kelp in the treatment of obesity, arteriosclerosis, and rheumatism and as a blood purifier. This results in fewer toxins entering the circulatory system. It also reduces caloric intake. Herbalists primarily employ kelp as a natural mineral supplement. Kelp is especially prized for its iodine content, used to treat hypothyroidism and obesity.