The science-backed benefits of sea moss (and possible side effects)

Irish sea moss has recently exploded in popularity as a superfood claimed to be capable of curing everything from low energy to skin woes and sluggish digestion. Sea moss supplements often come with compelling claims, but it’s crucial to separate marketing hype from scientific reality.

What is sea moss?

Sea moss, also known as Irish moss or Chondrus crispus, is a type of red algae that grows along the rocky Atlantic coasts, including the shores of Ireland.

Seaweeds have been a nutritional staple in coastal and Asian diets for centuries. They’re inherently rich sources of micronutrients, including:

• Vitamins: A, Bs, C, D, E, and K.
• Minerals: Iodine, iron, potassium, zinc, copper, magnesium, and calcium.
• Essential fatty acids and dietary fibre.

Are there science-backed benefits?

While there’s plenty of research around the health benefits of seaweed, there are limited studies about sea moss and its health benefits for humans.

Animal studies indicate potential prebiotic benefits, meaning the complex carbohydrates in the sea moss may help to feed beneficial gut bacteria and therefore support gut health. Other animal studies have shown antioxidant and anti-inflammatory effects due to its rich composition of polyphenols and other bioactive compounds.

These findings are typically based on studies using freeze-dried, ground seaweed rather than the overly processed form that we find in capsules these days.

The catch? Results from animal studies can’t be directly applied to human health, and the majority of claims surrounding common sea moss gels or supplements have yet to be verified in human clinical trials.

Are there known side effects?

There may be some concerns around the compound extracted from sea moss, commonly known as Carrageenan. It is often highly processed to create a thickener and emulsifier in common foods like ice-cream, jams, drinks and meat (often labelled as 407 on the ingredients list). 

Carrageenan is stripped of most of its nutritional benefits and is chemically different from the wholefood. Some research suggests that carrageenan may cause gut upset in some individuals, particularly those with Inflammatory Bowel Syndrome (IBS). Some studies have also shown that regular intake may also increase inflammatory markers.

Should you take sea moss supplements?

If you’re interested in the nutritional benefits of seaweed, less processed versions like seaweed flakes, Nori and whole sea moss are healthy foods to eat in moderation. If you’re considering a concentrated form like capsules or gel, it’s important to be mindful of the nutritional composition of the supplement and where it is sourced from.

Sea moss is rich in iodine, an essential nutrient for thyroid hormone production. However, consuming too much iodine can be harmful and may disrupt thyroid function for those with pre-existing conditions.

Seaweed naturally absorbs the nutrients and minerals from the water in which it grows. For wild-sourced sea moss, this process can also lead to the accumulation of heavy metals, which pose a significant health risk when consumed regularly and in concentrated forms.

The nutritional content of sea moss depends on the environmental conditions and waters where they’re grown. If buying Irish sea moss, it’s worth doing your research to understand where it’s grown and if it’s been tested for accurate nutritional information, including heavy metal contamination.

The bottom line

Think of sea moss as you would other wholefoods: its benefits lie in its natural, nutrient-dense state..

While whole sea moss (Chondrus crispus) shows potential in lab and animal research for its antioxidant and prebiotic effects, there’s currently not enough clinical evidence in humans to justify many of the health claims we see online.

Before starting any sea moss supplement, please consult with a healthcare professional. Focus on getting essential vitamins and minerals from a diverse diet rich in wholefoods first, and view sea moss as a nutritious dietary addition, not a miracle cure.

Reviewed by the Healthylife health experts October 2025.