Kelp, a brown seaweed available in capsule, liquid and tablet form, has a variety of purported medicinal benefits. It contains large amounts of iodine as well as essential vitamins and nutrients. According to the book "Prescription for Herbal Healing," kelp has a very high level of trace minerals. However, as with most herbal and alternative remedies, more research is needed to confirm the safety and effectiveness of kelp. Consult with your health care provider before incorporating kelp into your health care regimen.Weight loss ranks high on Memorial Sloan-Kettering Cancer Center's list of kelp's purported uses. According to the Center, iodine-rich kelp acts as a natural supplement for obesity. Because iodine stimulates thyroid function, it may increase the rate at which the body uses energy, thus reducing fat deposits. For this reason, kelp has a long history as a remedy to reduce cellulite, those lumps of fat that commonly appear on thighs.According to the University of Michigan Health System, kelp acts as a mild laxative to relieve constipation. Phyllis A. Balch, author of "Prescription for Herbal Healing," notes that almost 45 percent of kelp's weight consists of alginic acid, a dietary fiber that swells in water. Balch states, "Algin forms a gel within the intestines that coats and soothes the intestinal lining and softens the stool."Kelp acts a natural antioxidant. Unattached oxygen molecules, called free radicals, float freely through the body, creating damage to healthy cells. Kelp's nutrients and compounds have the ability to help neutralize free radicals. According to MayoClinic.com, antioxidants may assist the body in preventing cancer, among other illnesses. In addition, Memorial Sloan-Kettering Cancer Center claims that in a 2005 study conducted on rats, researchers at University of California, Berkeley, found that a diet containing kelp may help reduce a sex hormone linked to breast cancer. Findings indicate that kelp's hormone-modulating effect may work as an anti-estrogen to decrease the division of breast cells that have have DNA mutations, a risk factor for breast cancer. However, high-quality human studies are needed to confirm kelp's usefulness for the disease.Conflicting reports exist regarding kelp's efficacy as a treatment for hypothyroidism, otherwise known as underactive thyroid. Rich in iodine, kelp is used in herbal and alternative medicine to treat excessive functional activity of the thyroid, a gland vital in regulating normal growth and metabolism. Numerous human studies have examined the impact of kelp on the thyroid. A 2003 University of New Mexico study indicated that kelp stimulated slow metabolisms in postmenopausal women by increasing the level of thyroid-stimulating hormones. However, the MedlinePlus cautions that while research may point to kelp's effectiveness as a treatment for hypothyroidism, not enough evidence exists to fully support this claim. In fact, according to "Prescription for Herbal Healing," studies in Japanese coastal towns, where large quantities of kelp are consumed, show that a kelp diet may contribute to hypothyroidism. Researchers found that while regular consumption of kelp first stimulates thyroid activity, it may actually deplete activity with extended use.