Kelp, a type of brown seaweed, is used to support the glandular system primarily due to its high natural iodine content. Iodine is an essential trace element required for the synthesis of thyroid hormones, which are critical regulators of metabolism and are produced by the thyroid gland, a major component of the glandular (endocrine) system. Deficiencies in iodine can lead to thyroid dysfunction, including goiter and hypothyroidism. Multiple scientific studies have documented the role of dietary iodine, including from kelp and other seaweeds, in maintaining normal thyroid function (Leung et al., 2012). However, excessive intake of kelp can lead to excessive iodine consumption, which may cause thyroid dysfunction, particularly in susceptible individuals (Katagiri et al., 2014).

While the scientific evidence for kelp’s support of thyroid health via its iodine content is strong, there is less direct evidence for benefits to other glands of the endocrine system. Most clinical validation pertains to iodine-deficiency states. Thus, kelp's use for supporting the glandular system is considered scientifically justified, but primarily in the context of thyroid health. Caution is advised regarding dosing and potential contaminants (e.g., heavy metals) sometimes found in seaweed products.