As of 2015, kelp and kelp-based supplements are not known to have medically valid benefits for the thyroid, according to University of Utah Health Care. While iodine can treat certain thyroid-related disorders such as goiters and hyperthyroidism, kelp may contain amounts significant enough to cause hyperthyroidism or hypothyroidism.
Kelp may also worsen pre-existing thyroid conditions or cause heavy metal poisoning, warns University of Utah Health Care. Before undergoing kelp or any type of herbal supplementation, patients should first consult their doctors. Unsubstantiated medical benefits of kelp include improvement of sensory receptors, healthier nails and blood vessels, better digestion, easier weight management, decreased risk of breast cancer, and reduction of hair loss. Patients who take kelp should use only the dosage indicated in the instructions.