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Wood Ear Mushrooms
An under-utilized functional food
History
The term wood ear mushroom now refers to a number of species of morphologically similar jelly fungi, with wide distribution, and there is considerable genetic diversity within the Auricularia genus even within species. Wood ear mushrooms were among the most prized edible fungi in traditional Chinese medicine. There are records in China of wood ear mushrooms for culinary and medical use dating back nearly 1700 years, and the earliest cultivation records are from the 8th Century AD.

Despite their current obscurity outside of East Asia, wood ear mushrooms have a long history of use in European folk remedies. Wood ear mushrooms were commonly called Judas Ear mushrooms in the Middle Ages, according to the belief that they represented the incarnation of the spirit of Judas Iscariot, who hung himself from a tree after the execution of Jesus. In Europe, wood ear mushrooms were used to make tonics for congestion and sore throats. Chinese medicine considered soups made with wood ear to be an excellent fever reducer and treatment for consumption. Wood ear mushrooms have long been researched in East Asia, where studies have found anti-tumoral, anti-cancer, and cholesterol-lowering properties as well as improvements to liver function.
The Current Market

I can’t think of any bigger imbalance in the exotic mushroom market than wood ear mushrooms. This is a variety with over six million tons of annual production, consisting of up to 18% of the market for edible mushrooms globally. One sub-species is even endemic to Europe, and yet here is a mushroom variety that is almost utterly unknown outside of East Asia. Virtually no commercial cultivation takes place outside of East Asia, and indeed many Westerners have a strong aversive reaction to both the appearance and texture of this mushroom.

Essentially the only current market for wood ear mushrooms in Western markets is among East Asian, particularly Chinese, diaspora communities. This market is currently filled by inexpensive Chinese exports of dried wood ear mushrooms. Given these conditions, more than any other exotic mushroom varieties, wood ear mushrooms could benefit from having a spotlight shone on their status as a unique functional food even among mushrooms. Wood ear mushrooms will also require some work to demystify them as a food ingredient.

What’s Special about Wood Mushrooms
Wood ear mushrooms are about 66% carbohydrate by dry weight, a quarter of which consists of insoluble fibers. Wood ear mushrooms are remarkably low in calories, and lower in protein than other mushrooms. Per 100-gram serving (raw), wood ear mushrooms have 14 calories compared to 25 calories for shiitake, and just 0.7 grams of protein compared to 3.1 for shiitake. The same serving of wood ear mushrooms has 5.5 grams of fiber_emdash_compared to 4.9 for shiitake and 2 grams for common button mushrooms (all figures from the Japanese Ministry of Ministry of Education, Culture, Sports, Science and Technology, or MEXT for short). Wood ear mushrooms also have a much lower ash content than most other mushrooms, and the fruiting bodies are rich in a number of compounds not found in other fungi.

Looking at micronutrients and vitamins, wood ear mushrooms vary so much between different varieties of spawn and are also extremely sensitive to substrate, that I find it difficult to offer an accurate assessment. There are widely variant figures between the nutrition database MEXT publishes, the USDA, and the figures in various research papers I have read on the variety. However, wood ear mushrooms appear to be high in calcium, iron, and magnesium, while being very low in potassium compared to other varieties of edible fungi. Magnesium is a vital mineral generally lacking in modern Western diets and is important for maintaining bone health, cellular health, cardiovascular health, and aiding muscle recovery after exercise. Wood ear mushrooms, especially sun-dried, are rich in vitamin D, and are modest sources of ergosterol and the proposed antioxidant ergothioneine.
Just perusing the nutrition tables does not, however, reveal the whole story. After reading through the nutrition facts, a consumer could be forgiven for thinking wood ear mushrooms don’t really have much to offer, given how low the content of the various vitamin B complexes is compared to other mushrooms. However, wood ear fungi have two special traits that make them worth another look among fungi. Wood ear mushrooms 1) are a rich source of unique antioxidants, and 2) contain a diverse and complex array of polysaccharides in higher proportions than other species of mushrooms.

Antioxidant properties of wood ear mushrooms
Every mushroom, and exotic mushroom varieties in particular, are rich sources of antioxidants. One example is the fungal antioxidant ergothioneine, covered in the 2023 Fall issue. Wood ear mushrooms are not a particularly rich source of ergothioneine, especially compared to oyster mushroom varieties. Wood ear mushrooms do have, however, a high concentration of phenolic compounds and flavonoids not found in other mushrooms.
The dark coloration of wood ear mushrooms is a result of melanin, a natural pigment (the same that gives rise to variations in human skin tones) that has been found to have antioxidant and antitumoral properties. Studies on the antioxidizing capacity of wood ear mushrooms have found a wide range of antioxidant activity, including metal chelating capacity. Comparisons of different varieties of wood ear mushrooms found all were capable of reducing ferric iron and scavenging hydroxyl groups.

Polysaccharide rich
Wood ear mushrooms have a pectin content ranging from 3~8%. Pectin is a complex polysaccharide considered to be a soluble fiber. In the gastrointestinal system, pectin reduces cholesterol absorption and lowers the glycemic index of foods. Pectin, like beta-glucans, does not refer to one single organic molecule, but to a diverse range of molecular compounds with similar structures and properties. Most commercial pectin is extracted from citrus fruits or apple pomace, and pectin can have wide variation in chemical structure and bioactivity depending on the source and processing method. In addition, pectin, like beta-glucans, is a beneficial prebiotic that serves as fuel for the microorganisms involved in the digestion and absorption of food in the intestines. These microorganisms break the pectin down into short chain fatty acids (SCFAs).
The beta-glucan content of wood ear mushrooms is actually lower than shiitake and other exotic mushroom varieties, at around 15% dry weight. There is evidence, however, that the particular beta-glucan compounds within wood ear mushrooms have an especially complex structure and have high bioactivity. Research from China and Japan has shown wood ear mushrooms to have a protective effect against colorectal cancer and to have strong antitumoral and immunostimulating properties. Wood ear mushrooms are also rich in other polysaccharides like mannose that can also serve as a prebiotic in the intestines.

Research suggests that rather than looking at raw content of beta-glucans as a percentage, equally important are the structural complexity and variety of different beta-glucan compounds as well as their bioavailability from the food matrix. In China, wood ear mushrooms are commercially harvested for their polysaccharides for use in a wide variety of health and food products, including fruit juices and jellies. More than any other exotic mushroom, I see great potential in wood ear for its use as a food additive, both to provide pectin or beta-glucan fibers to food, and also for its natural melanin pigment.
The gut microbiota
The gastrointestinal tract, and especially the gut microbiota_emdash_the ratios of different bacterial species residing in the gut_emdash_are not a glamorous part of medicine or nutrition research. This subject is also a particularly complex one, but it bears noting that there are one hundred trillion microbes in an adult human gastrointestinal tract. This gut microbiota is now increasingly thought of as a hidden, additional organ in the human body, one which contains upwards of a thousand different bacteria species.

The gastrointestinal tract is not only the gateway for absorbing all the nutrients a human body requires for daily function, but it also simply constitutes a huge portion of the human body. Research has linked dysfunctions in the intestinal barrier (leaky gut) and other inflammatory GI conditions to a number of diseases. Even more nonintuitively, diseases such as Alzheimer’s, Parkinson’s, and auto-immune disorders have also been found to have connections to the gut microbiota and the gastrointestinal system. Health issues as diverse as metabolic syndrome and obesity, and frailty and dementia in the elderly, have been found in research to be heavily influenced by the ratio of bacteria species and the health of the gut microbiota.

In a study looking at obesity in mice using simulated high fat diets versus a control versus a high fat diet supplemented with wood ear polysaccharides, researchers found that mice on the high fat wood ear supplemented diet not only lost weight compared to the non-intervention group, but also had higher concentrations of SCFAs in stool samples than the control group on the standard diet. SCFAs play a number of critical roles in the health of the large intestine, as they are the primary energy source for the epithelial cells that line the large intestine. Butyrate in particular is an SCFA that has been highlighted in research for regulating inflammation in the large intestine and suppressing the population of certain harmful species of bacteria. Butyrate also appears to influence both blood sugar and appetite. Studies have found that low rates of butyrate in stool correlate with obesity and higher risks of intestinal cancers.

Compared to cellulose and other common sources of fiber, bacteria in the gastrointestinal tract more readily ferment beta-glucans, pectin, and resistant starches. As a result, these forms of fiber lead to much higher levels of butyrate and other SCFAs. In the study referenced above, mice with the wood ear supplemented diet had rates of butyrate nearly forty times higher than the non-intervention high-fat diet mice. Even more interestingly, mice in this group had four times the butyrate levels of the control group of mice on a standard, balanced diet formulation. A total measure of SCFA content found the wood ear supplemented mice ended the study with nearly triple the SCFA content as the healthy control group, and nearly five times that of the non-supplemented high-fat group. The same study also found that wood ear mushroom supplemented diets modified the composition of the gut microbiota in mice, increasing concentrations of species thought to be beneficial and restricting the proliferation of harmful bacteria species.

Wrapping up wood ear mushrooms
As wood ear mushrooms and their benefits are both unique and not widely known in Western markets, they are worth highlighting in a standalone health-related article. Wood ear mushrooms deserve a second look, both from exotic mushroom farming operations in Western countries and a new generation of younger and more health-conscious consumers. There are many unique qualities to wood ear mushrooms, including beta-glucan and other soluble fibers that may have higher bioactivity and thus are more potent as nutraceuticals than other mushroom varieties. Wood ear mushrooms also contain many phenolic antioxidant compounds not found in other mushrooms.

Polysaccharide extracts from dried wood ear mushrooms have wide potential use in food industries as a healthy additive to flours for bread and pasta. Wood ear mushrooms could also provide natural food colorations and serve as a food preservative antioxidant. Wood ear mushrooms have enormous potential for the food processing and health food sector. Additionally, wood ear mushrooms are a summer variety, with some varieties capable of fruiting in temperatures as warm as 28~31 degrees Celsius (82~88 degrees Fahrenheit), making them ideal for farms in warm climates to reduce summer climate control costs by shifting to wood ear production.

Wood ear mushrooms fit neatly into the puzzle of mushroom production, filling a unique niche. The mushroom industry needs to embrace diversity, allowing for a number of different fungal species to be cultivated commercially in order to maximize ecological efficiency and take advantage of the different nutritional and culinary uses of each variety. At the same time, consumers can also benefit from a diverse and healthy diet rich in a number of different mushroom varieties to maximize the cholesterol-lowering and immunostimulating properties of fungi.
^{Partial List of References:
Kadnikova, Irina & Costa, Rui & Kalenik, Tatiana & Guruleva, Olga & Yanguo, Shi. Chemical Composition and Nutritional Value of the Mushroom Auricularia auricula-judae. Journal of food and nutrition research, Issue 3, 2015. 478-482.
Huan Xiang, Dongxiao Sun-Waterhouse, Chun Cui. Hypoglycemic polysaccharides from Auricularia auricula and Auricularia polytricha inhibit oxidative stress, NF-κB signaling and proinflammatory cytokine production in streptozotocin-induced diabetic mice. Food Science and Human Wellness, Volume 10, Issue 1, 2021, 87-93.
Tahidul Islam, Fangjie Yao, Wenyi Kang, Lixin Lu, Baojun Xu. A systematic study on mycochemical profiles, antioxidant, and anti-inflammatory activities of 30 varieties of Jew’s ear (Auricularia auricula-judae). Food Science and Human Wellness, Volume 11, Issue 4, 2022, 781-794.
Tingting Zhang, Wenying Zhao, Beizhen Xie, Hong Liu. Effects of Auricularia auricula and its polysaccharide on diet-induced hyperlipidemia rats by modulating gut microbiota. Journal of Functional Foods, Volume 72, 2020, 104038.}

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Wood Ear Mushrooms

An under-utilized functional food