sea moss

Sea moss is a red seaweed (most often Chondrus crispus, also called Irish moss) sold as a raw "gel," dried, or in capsule and powder supplements. Like other seaweeds it is naturally rich in iodine and other minerals, and it is a source of the polysaccharide carrageenan.

There is no NIH Office of Dietary Supplements or NCCIH fact sheet specifically for sea moss, and rigorous human evidence that it treats, prevents, or improves any health condition appears to be limited. Most marketing claims rest on its nutrient and iodine content rather than on controlled studies in people, so its specific health benefits are not established. Treat efficacy claims with caution and do not rely on it to treat any medical condition.

There is no established or standardized supplement dose for sea moss, and iodine content can vary widely between products. Because seaweed can deliver large and unpredictable amounts of iodine (adults need only about 150 micrograms daily, per MedlinePlus, and very high intake can affect the thyroid), talk to a clinician or pharmacist before using it, especially if you are pregnant, breastfeeding, or have a thyroid condition.

Sea moss, like other seaweeds, can be high in iodine, and too much iodine can disrupt thyroid function. MedlinePlus notes that very high iodine intake can reduce thyroid function, and that iodine from "seaweed and seaweed-based supplements" can also contribute to an overactive thyroid (hyperthyroidism). Separately, seaweed can concentrate heavy metals such as arsenic, lead, cadmium, and mercury from the water it grows in; this is a commonly reported concern for seaweed products generally, though it is not addressed in the cited MedlinePlus pages. People who are pregnant or breastfeeding, who have thyroid disease, or who take thyroid medicine should be especially cautious and consult a clinician first.

Reported concerns are driven mainly by its iodine load. Per MedlinePlus, too much iodine can cause an overactive thyroid, with symptoms such as nervousness or irritability, a rapid or irregular heartbeat, weight loss, and trouble tolerating heat; very high iodine intake can also reduce thyroid function. Digestive upset may also occur (anecdotally), and possible contamination with heavy metals is a long-term safety concern for seaweed products in general.

Because sea moss can add a substantial amount of iodine, it may interact with thyroid and anti-thyroid medications. MedlinePlus states that combining high doses of iodine with anti-thyroid medicines can have an additive effect that could lead to an underactive thyroid (hypothyroidism). Discuss sea moss with your clinician if you take thyroid medication, other iodine-containing products, or have any chronic condition.