Is sea moss (Irish moss) a worthwhile supplement?

Sea moss (Chondrus crispus, also known as Irish moss) is naturally low in fat, moderately high in protein and rich in carbohydrates. It is a good source of minerals such as zinc. These are established compositional facts, but they say nothing about whether your body actually absorbs those nutrients, or about any health effect you might notice.

In laboratory research on cells, there are some interesting signals. Fatty extracts of sea moss inhibited inflammatory pathways in human immune cells. Carrageenan, a carbohydrate from this type of seaweed, inhibited the growth of cancer cells in a culture dish by as much as 91%. Crude extracts also showed antimicrobial activity. These are, however, purely laboratory findings. A culture dish is not a human being, and going from these results to an effective supplement is a long step.

There are no clinical studies or randomised trials in humans showing that sea moss as a supplement does anything for your health. They simply do not exist. The only human-oriented study that comes close looked at sea moss as a bread ingredient: adding 2% to wholegrain bread produced an acceptable product with slightly more fibre and minerals. Higher percentages tasted less pleasant. But that concerns food, not capsules or powders.

Sea moss supplements are sold online, sometimes with far-reaching health claims. That they contain bioactive compounds is scientifically plausible, but whether those compounds also work in humans when taken as a supplement, and at what dose, is entirely unknown. In addition, seaweeds can contain iodine and heavy metals in varying concentrations, which may pose risks at high intakes, although that is not covered by the sources available here.