Sea moss

Also known as irish moss, chondrus crispus, seamoss.

Last reviewed October 9, 2026 · Jump to references

What is Sea moss?

In plain words

Sea moss is a red seaweed sold as food, gels, and supplements. The body uses its iodine to make thyroid hormones, while much of its fiber passes through without being digested. Researchers study its nutrients and effects on gut health, but human evidence for benefits from sea moss supplements is limited. Iodine levels vary, and too much can disrupt thyroid function; seaweed can also contain heavy metals.

Technical definition

Sea moss typically refers to Chondrus crispus (Irish moss), a red macroalga containing carrageenan sulfated polysaccharides, minerals, and variable amounts of iodine; the commercial name also encompasses other red algae. It has no single molecular target: absorbed iodine supports thyroid hormone synthesis, while its polysaccharides largely resist human digestive enzymes. It is marketed as a food or dietary supplement, not an FDA-approved treatment for disease.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.