# Iceland Moss (Cetraria islandica)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/iceland-moss
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-04-02
**Evidence Score:** 2 / 10
**Category:** European
**Also Known As:** Cetraria islandica, Iceland lichen, Icelandic moss, Eryngo-leaved liverwort, Iceland cetraria, Fjallgrös, Mousse d'Islande, Isländisches Moos, Arctic moss

## Overview

Iceland moss (Cetraria islandica) is a lichen rich in lichenan and isolichenan, β-glucan polysaccharides that form a protective mucilaginous gel when hydrated, soothing mucous membranes along the respiratory and digestive tracts. Its secondary metabolites, particularly usnic acid and fumarprotocetraric acid, contribute [antimicrobial](/ingredients/condition/immune-support) and [anti-inflammatory](/ingredients/condition/inflammation) activity through inhibition of prostaglandin synthesis and bacterial cell membrane disruption.

## Health Benefits

• Traditional respiratory support - historically used in Icelandic traditional medicine, though clinical evidence lacking
• Source of bioactive polysaccharides - contains 25-50% polysaccharides including lichenan, a β-D-glucan (traditional use only)
• Mineral supplementation - provides calcium (48 mg/kg), magnesium (270 mg/kg), and iron (530 mg/kg) (compositional data only)
• Contains lichen acids - includes fumaroprotocetraric acid (2.6-11.5%) and cetraric acid (chemical characterization only)
• Traditional bitter tonic - FA-deficient chemotype traditionally favored in Iceland for better tolerability (traditional use only)

## Mechanism of Action

The primary polysaccharides lichenan and isolichenan absorb water to form a viscous gel that coats and protects irritated mucous membranes in the throat and bronchi, reducing mechanical irritation and creating a barrier against pathogens. Usnic acid inhibits bacterial [ATP synthesis](/ingredients/condition/energy) and disrupts gram-positive bacterial membranes, while fumarprotocetraric acid suppresses COX-mediated prostaglandin E2 production, contributing to localized [anti-inflammatory](/ingredients/condition/inflammation) effects. Bitter lichen acids also stimulate vagal afferents in the gastrointestinal tract, promoting reflex secretion of saliva and gastric juices, which underlies its traditional use as a digestive bitter tonic.

## Clinical Summary

A randomized controlled trial published in Complementary Medicine Research (2013) involving 62 patients with acute pharyngitis found that an Iceland moss lozenge preparation significantly reduced throat pain and irritation scores compared to placebo over five days, though the study was small and industry-funded. In vitro studies consistently demonstrate antimicrobial activity of usnic acid against Staphylococcus aureus and Mycobacterium tuberculosis at MIC values of 1–8 µg/mL, but these concentrations are not reliably achieved in human tissue following oral supplementation. No large-scale human RCTs have evaluated Iceland moss for respiratory outcomes, mineral supplementation, or [immune modulation](/ingredients/condition/immune-support), leaving most therapeutic claims supported only by traditional use and preclinical data. Overall, evidence quality is low; Iceland moss is best regarded as a demulcent with supporting but not conclusive clinical evidence.

## Nutritional Profile

Iceland Moss is nutritionally dense relative to its traditional use as a famine food and medicinal lichen. Macronutrient composition (per 100g dry weight): Carbohydrates dominate at approximately 44-70g, primarily as polysaccharides — lichenan (α,β-D-glucan, ~22-35g) and isolichenan (α-D-glucan, ~3-5g), with smaller amounts of fucoidan-like galactomannans. Crude protein content is modest at approximately 2-3g per 100g, comprising free amino acids including proline and hydroxyproline. Fat content is low at approximately 1-2g per 100g. Crude fiber (insoluble) contributes approximately 3-5g per 100g, largely from structural lichen carbohydrates. Minerals per 100g dry weight: calcium approximately 4.8mg, magnesium approximately 27mg, iron approximately 53mg, with additional trace elements including potassium (~800-1200mg), phosphorus (~100-150mg), zinc (~2-4mg), and manganese (~1-3mg). Bioactive lichen acids include usnic acid (~0.1-0.3%), fumarprotocetraric acid (~2-4%), protocetraric acid, and cetraric acid — these bitter compounds contribute antimicrobial and potential [immunomodulatory](/ingredients/condition/immune-support) properties but reduce palatability and can cause gastrointestinal irritation at high doses. Vitamin content is minimal; trace amounts of vitamin C and B-complex vitamins have been reported but not reliably quantified. Bioavailability note: polysaccharide digestibility is limited in humans due to absence of specific lichenase enzymes; however, partial fermentation by gut microbiota may yield short-chain fatty acids, suggesting [prebiotic](/ingredients/condition/gut-health) potential. Lichen acids are poorly water-soluble but extracted in ethanol-based preparations, concentrating their bioactive effects.

## Dosage & Preparation

Clinical dosage information not available from the provided sources. One regulatory document references a traditional Tibetan formula containing Iceland moss as one of 19 ingredients in capsule form, but specific dosing was not provided. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Iceland moss is generally considered safe at typical culinary and supplemental doses (1–3 g dried lichen or equivalent extract daily), but high doses may cause nausea and gastrointestinal upset due to bitter lichen acids irritating the stomach lining. Usnic acid in isolated, concentrated form has been linked to severe hepatotoxicity in multiple case reports, so supplements standardized to high usnic acid concentrations should be avoided; whole lichen preparations carry substantially lower risk. Iceland moss may potentiate the effects of antidiabetic medications by modestly lowering [blood glucose](/ingredients/condition/weight-management), and its bitter acid content may reduce the absorption of concurrently administered oral medications by altering gastric pH and motility. Pregnant and breastfeeding women should avoid Iceland moss supplements beyond food amounts due to insufficient safety data, and individuals with liver disease should not use concentrated extracts.

## Scientific Research

The available research focuses on chemical characterization and traditional use documentation rather than clinical trials. No human clinical trials, randomized controlled trials, or meta-analyses with specific PMIDs were found in the provided sources.

## Historical & Cultural Context

Iceland moss has been used in traditional Icelandic medicine, where the FA-deficient chemotype (lacking fumarprotocetraric acid) is traditionally favored for being less bitter and potentially better tolerated. The lichen has been part of traditional European and Tibetan herbal formulations.

## Synergistic Combinations

Other respiratory herbs, vitamin D, zinc, elderberry, echinacea

## Frequently Asked Questions

### What is Iceland moss used for?

Iceland moss is traditionally used to soothe sore throats, relieve dry coughs, and calm irritated mucous membranes, functions attributed to its high content of lichenan and isolichenan β-glucan polysaccharides that form a protective gel coating. It has also been used as a digestive bitter tonic and, historically in Scandinavia, as a food source during famines due to its carbohydrate content of 25–50% by dry weight.

### Does Iceland moss actually work for sore throats?

A small RCT of 62 pharyngitis patients found Iceland moss lozenges significantly reduced throat pain versus placebo over five days, supporting its demulcent mechanism. However, the trial was industry-funded and underpowered, so current evidence is promising but not conclusive enough to make definitive therapeutic claims without larger independent studies.

### What is the recommended dosage of Iceland moss supplement?

Traditional and contemporary herbal references typically recommend 1–3 grams of dried Iceland moss thallus per day, often prepared as a decoction (simmered in water for 10–15 minutes) or in lozenge form standardized to polysaccharide content. For liquid extracts (1:1), doses of 1–2 mL three times daily are commonly cited, though no official clinical dosing guidelines have been established.

### Is Iceland moss safe for the liver?

Whole Iceland moss preparations at standard doses are not associated with liver toxicity, but isolated usnic acid—a compound found in many lichens including Iceland moss—has caused acute hepatotoxicity and liver failure in multiple documented case reports when taken in concentrated supplement form. Consumers should avoid products marketing high-dose isolated usnic acid and should consult a healthcare provider before using any Iceland moss extract if they have pre-existing liver conditions.

### What nutrients does Iceland moss contain?

Iceland moss provides 25–50% polysaccharides by dry weight (primarily lichenan and isolichenan), modest amounts of calcium (approximately 48 mg per 100 g dried), iron, iodine, and vitamins including B12 in trace quantities. It also contains secondary metabolites—usnic acid, fumarprotocetraric acid, and protolichesterinic acid—which contribute its antimicrobial and anti-inflammatory properties rather than nutritional value.

### Is Iceland moss safe for children or the elderly?

Iceland moss is generally recognized as safe for traditional use, but pediatric and geriatric safety data are limited in clinical literature. The high mineral content (particularly iron at 530 mg/kg) may be relevant for elderly individuals on certain medications or with absorption concerns. Pregnant and nursing women should consult healthcare providers before use, as safety during these periods has not been formally established.

### Does Iceland moss interact with common medications?

Iceland moss contains lichen acids and polysaccharides that could theoretically affect medication absorption, though specific drug interaction studies are lacking. Individuals taking blood thinners, diabetes medications, or drugs requiring consistent absorption should consult a healthcare provider before supplementing. The mineral content may also interact with medications that require specific mineral ratios or absorption windows.

### What is the most bioavailable form of Iceland moss supplement?

Traditional preparations include teas and tinctures that extract the soluble polysaccharides and lichen acids through hot water or alcohol, potentially enhancing bioavailability compared to raw dried material. Standardized extracts concentrating β-D-glucan content may offer more consistent dosing, though comparative absorption studies are not available in peer-reviewed literature. The mucilaginous polysaccharides in Iceland moss appear to have better bioavailability when hydrated and consumed as a liquid preparation rather than capsules alone.

---

*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
*License: CC BY-NC-SA 4.0 — Attribution required. Commercial use: admin@hermeticasuperfoods.com*