The use of kelp (various species of seaweed) for supporting or treating goiter is primarily justified by scientific evidence. Goiter, an enlargement of the thyroid gland, is most commonly caused by iodine deficiency. Kelp is a rich natural source of iodine, an essential micronutrient required for the synthesis of thyroid hormones. Historically, populations with diets deficient in iodine—especially those living inland or far from the sea—were more susceptible to goiter. Supplementation with iodine, including via kelp, has long been recognized as an effective preventive and therapeutic measure for simple (iodine-deficiency) goiter.

Modern scientific research and public health interventions have confirmed the role of iodine in preventing and managing goiter. The introduction of iodized salt and, in some cases, seaweed supplements like kelp, has led to a marked decrease in goiter prevalence worldwide. Clinical guidelines recognize iodine supplementation as standard care for iodine-deficiency goiter, and kelp is an established natural source. However, excessive iodine intake, including overconsumption of kelp, can potentially lead to thyroid dysfunction, so dosage is important.

In summary, there is strong scientific validation for the use of kelp as a source of iodine in the prevention and treatment of iodine-deficiency goiter, though care must be taken regarding dosing to avoid iodine excess and related thyroid problems.