Bai Mu Er
StarTremella fuciformis Berk.
Traditionally used for
- Ears & hearing
- Nose & throat
- Cough & breathing
- Colds & fever
- Digestion
- Bowel health
- Energy & fatigue
Cautions & contraindications
- Toxic — professional use only
☯ TCM Properties
Nourishes Lung Yin; Benefits the Stomach and Generates Fluids; Tonifies Qi; Moistens the Intestines and Unblocks the Bowels
Traditional Chinese Uses
Bai Mu Er (white wood ear fungus, silver ear mushroom) is a neutral, sweet herb that nourishes Lung and Stomach Yin and generates Body Fluids. It is used for dry cough, dry throat, thirst, and the residual symptoms of febrile illness that depleted Body Fluids. As a food-grade tonic, it is commonly cooked in sweet soups with rock sugar and wolfberries as a classic Chinese dietary remedy for Lung Yin deficiency and dry respiratory conditions.
Western Herbalism Properties
Relationships
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Botanical Description
Tremella fuciformis, known as snow fungus, white jelly mushroom, or silver ear, is a basidiomycete jelly fungus in the family Tremellaceae, distributed across tropical and subtropical regions worldwide, including East and Southeast Asia, Australia, Africa, and the Americas, where it grows as a parasite on the mycelium of wood-decaying Annulohypoxylon ascomycetes inhabiting fallen broadleaved logs. The fruiting body is gelatinous, translucent, and pure white to pale yellowish when fresh, drying to a brittle ivory-cream mass; it consists of numerous thin, ruffled, leaf-like or seaweed-like lobes radiating from a central base, the entire structure reaching 5-15 cm across. The texture is firm-jellied and rubbery when hydrated. Microscopically the hymenium bears characteristic longitudinally septate basidia that produce ellipsoid basidiospores. The species is widely cultivated commercially in China by inoculation onto sterilized substrate logs alongside its host fungus and is used both as food and as a tonic.
Active Constituents
Glucuronoxylomannan (Tremella fuciformis polysaccharide, TFP)
Acidic heteropolysaccharideConcentration: the dominant constituent of the dried fruiting body and the fraction all Tremella pharmacology refers to
An acidic heteropolysaccharide built on a linear alpha-(1 to 3)-D-mannan backbone, heavily substituted at the C-2 position of the mannose residues with beta-D-xylose, beta-D-glucuronic acid and beta-(1 to 2)-linked D-xylobiose. The glucuronic acid residues give it its acidic character and its extreme water-binding capacity, which is what makes rehydrated Yin Er gelatinous and is the physical basis of the classical moistening and fluid-generating action. It is also the fraction used in the two human trials on this fungus.
Beta-glucan (soluble fungal glucan fraction)
PolysaccharideConcentration: 6.4 g per 180 mL in the beverage used in the 12-week prediabetes randomised trial
The soluble glucan load is the plausible active in the metabolic trial, acting through viscosity, delayed gastric emptying and slowed carbohydrate absorption rather than any receptor-level mechanism. Note the dose: 6.4 g of beta-glucan per serving is a food-scale, not a decoction-scale, exposure.
Uronic acid-rich polysaccharide fractions
Polysaccharide (uronic acid-rich)Fractions enriched in uronic acid are the ones reported to reduce adiposity in high-fat-diet mice. Monosaccharide analyses of purified Tremella fractions vary between studies, with mannose, xylose, glucuronic acid, glucose, galactose and fucose all reported in differing ratios, so a given commercial extract is not interchangeable with the fraction used in any particular paper.
⚠ Drug Interactions
Bongkrekic acid produced by Burkholderia gladioli pathovar cocovenenans in spoiled or over-soaked fungus
This is not a herb-drug interaction but the single serious hazard of this food-medicine, and practitioners should state it to patients rather than assume it is common knowledge. Burkholderia gladioli pathovar cocovenenans is a soil and plant bacterium that, on wet starchy or fungal substrate at near-neutral pH and ambient temperature, produces bongkrekic acid. Bongkrekic acid binds the mitochondrial adenine nucleotide translocase and locks it in the m-state, abolishing ATP/ADP exchange across the inner mitochondrial membrane, so cellular energy production stops in the most metabolically active organs first: liver, brain, heart and kidney. Reported LD50 ranges are 1 to 3.16 mg/kg in humans and 0.68 to 6.84 mg/kg in mice, so a few milligrams is a lethal adult dose.
Two points make this a practical danger rather than a theoretical one. First, the toxin is heat-stable: boiling and even pressure cooking do not destroy it, and it cannot be washed off. Second, Tremella is one of the principal vehicles. Of 19 bongkrekic acid outbreaks reported to the China National Foodborne Disease Outbreak Surveillance System between 2010 and 2020 (146 illnesses, 139 hospitalisations, 43 deaths, case-fatality rate 29.5%), the single largest outbreak, 52 cases, was linked to Tremella fuciformis; homemade fermented cereal products, tremella and starch jelly dominated the earlier years, with wet rice noodles and Auricularia auricula appearing later. Spoiled fresh (undried) Tremella and rehydrated fungus left standing are the specific conditions implicated. The same mechanism and the same organism account for the well-publicised wood ear (Auricularia) poisonings.
Clinical note: Tell patients: soak Yin Er on the day it is to be eaten and cook it the same day; if overnight soaking is unavoidable, soak it in the refrigerator; discard any batch that has been standing at room temperature for 24 hours or more, and discard fresh undried Tremella that is at all slimy, discoloured or off-smelling, regardless of how it will be cooked. Cooking is not a rescue. A patient presenting with vomiting, abdominal pain and then rapidly deteriorating liver function after a Tremella dish is a medical emergency for hospital transfer, not a case for herbal management.
Insulin, metformin, sulfonylureas and other glucose-lowering therapy
In a 12-week double-blind randomised trial in 56 overweight or obese prediabetic adults, a 180 mL daily beverage delivering 6.4 g of Tremella fuciformis beta-glucan lowered HbA1c from 6.03 plus or minus 0.16% to 5.96 plus or minus 0.25% (p = 0.047, Cohen's d 0.39) and waist circumference from 95.2 plus or minus 12.51 cm to 93.46 plus or minus 11.48 cm (p = 0.022, Cohen's d 0.45), with no change in the placebo arm. Fasting glucose, lipids and insulin sensitivity measures did not change. The mechanism is most likely the viscous soluble fibre load slowing carbohydrate absorption, not a pharmacological insulin-sensitising action.
Clinical note: The effect is real but small (roughly 0.07 percentage points of HbA1c) and does not by itself require dose adjustment. It matters when Yin Er is eaten daily as a food in a patient on insulin or a sulfonylurea and titrating close to hypoglycaemia; ask about it when reviewing a glucose log rather than treating it as a hidden hypoglycaemic.
Cholinesterase inhibitors and other cognitive-symptom therapy
In an 8-week randomised, double-blind, placebo-controlled trial, 75 adults with subjective cognitive impairment received Tremella fuciformis 600 mg/day (n = 30), 1200 mg/day (n = 30) or placebo (n = 15). The Tremella groups improved more than placebo on total subjective memory complaint questionnaire score, with exploratory imaging showing group-by-visit interactions in left precuneus, right supramarginal gyrus, right middle frontal gyrus and right postcentral gyrus at corrected p < 0.05. Adverse event frequency did not differ between high-dose (40.4%), low-dose (35.1%) and placebo (41.4%) groups. This is a single small trial in subjective complaints, not in diagnosed cognitive impairment, and there is no pharmacokinetic interaction on record with donepezil or memantine.
Clinical note: Reasonable to use alongside conventional care. The thing to guard against is a patient with progressive objective memory loss deferring neurological assessment because a supplement helped their subjective complaint score.
Evidence Tier
Moderate evidence · 3 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
2
1 verified · 1 unverified
Other clinical trial
0
Observational / case report
0
In vitro / animal
0
Other / unclassified
1
0 verified · 1 unverified
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Efficacy and Safety of Tremella fuciformis in Individuals with Subjective Cognitive Impairment: A Randomized Controlled Trial
Eight-week randomised, double-blind, placebo-controlled trial in 75 adults with subjective cognitive impairment, allocated to Tremella fuciformis 600 mg/day (n = 30), 1200 mg/day (n = 30) or placebo (n = 15). The primary endpoint was change in total score on the subjective memory complaint questionnaire, with short-term memory and executive function as secondary endpoints. The Tremella groups improved more than placebo on the primary endpoint, and exploratory neuroimaging found significant group-by-visit interactions in the left precuneus, right supramarginal gyrus, right middle frontal gyrus and right postcentral gyrus at corrected p < 0.05. Adverse events were comparable across high-dose (40.4%), low-dose (35.1%) and placebo (41.4%) arms. Small, single-centre, and in subjective rather than objectively confirmed impairment.
Tremella fuciformis beverage improves glycated hemoglobin A1c and waist circumference in overweight/obese prediabetic subjects: a randomized controlled trial
Twelve-week double-blind randomised controlled trial in 56 overweight or obese prediabetic adults (28 intervention, 28 placebo), given one 180 mL beverage daily containing Tremella fuciformis with 6.4 g beta-glucan, or placebo. HbA1c fell from 6.03 plus or minus 0.16% to 5.96 plus or minus 0.25% (p = 0.047, Cohen's d 0.39) and waist circumference from 95.2 plus or minus 12.51 cm to 93.46 plus or minus 11.48 cm (p = 0.022, Cohen's d 0.45); the placebo arm changed on neither. Fasting glucose, lipids and insulin sensitivity indices were unchanged. Compliance averaged 98.81 plus or minus 3.16% and no adverse events were reported. The effect sizes are small and the endpoint changes are of borderline clinical magnitude.
Epidemiology of foodborne bongkrekic acid poisoning outbreaks in China, 2010 to 2020
Analysis of the 19 bongkrekic acid outbreaks reported to the China National Foodborne Disease Outbreak Surveillance System over 2010 to 2020: 146 illnesses, 139 hospitalisations and 43 deaths, a case-fatality rate of 29.5%. The single largest outbreak in the period, 52 cases, was associated with Tremella fuciformis and involved commercially retailed food in Shandong in 2012. Homemade fermented corn flour products, tremella and sweet potato or corn starch jelly dominated the earlier outbreaks; wet rice noodles and Auricularia auricula appeared as vehicles later in the period. Long-term or improper storage of wet fermented cereal, white fungus and potato products is identified as the condition favouring the organism.
Historical Texts
Ben Cao Zai Xin
Qing dynastyBen Cao Wen Da
Qing dynastyYin Pian Xin Can
Republican era (1936)References
- Han Dong; Chen Jian; Chen Wei; Wang Yanbo. Bongkrekic Acid and Burkholderia gladioli pathovar cocovenenans: Formidable Foe and Ascending Threat to Food Safety . Foods (2023) [DOI]
- Rui Yanlin; Lee Quancen; Guo Yue; Huang Ying; Xu Huanyi; Liu Bin; Ge Xiaodong; Lin Hua; Zeng Feng. Structure, Function and Application of Tremella Fuciformis Polysaccharide: A Review . Journal of Food Science (2025) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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