Lentinula edodes, Shitake
Lentinus edodes, named as Shiitake in Japan, has been cultivated for thousands of years in China.
This is a tender and tasty mushroom found in many Asian cuisines. It is considered both a delicacy and a medicinal mushroom.
Among others, Shiitake is valued as an anticancer agent: Lentinan, a compound found in Shitake, is used as an intravenous anti-cancer drug with antitumor properties.
Clinical studies have associated lentinan with a higher survival rate, higher quality of life and lower recurrence of cancer.
Shiitake contains the scientifically verified bioactive compounds with important roles in support of the immune system and improvement of bone health.
Shiitake can also lower levels of bad cholesterol and promote heart health.
Scientific names: Lentinus edodes (Berk.) Pegler, Kavaka.
Synonyms: Agaricus edodes Berk., Armillaria edodes (Berk.) Sacc., Mastoleucomychelloes edodes (Berk.) Kuntze, Cortinellus edodes (Berk.) S.Ito & S.Imai, Lentinus edodes (Berk.) Singer, Collybia shiitake J.Schröt., Lepiota shiitake (J.Schröt.) Nobuj. Tanaka, Cortinellus shiitake (J.Schröt.) Henn., Tricholoma shiitake (J.Schröt.) Lloyd, Lentinus shiitake (J.Schröt.) Singer, Lentinus tonkinensis Pat., Lentinus mellianus Lohwag.
Common names: Shiitake, Sawtooth Oak mushroom, Black Forest Mushroom, Black mushroom, Golden Oak Mushroom, Oakwood Mushroom, The Elixir of Life.
Japanese name: Shiitake.
Chinese name: Donggu, Xiagu, Xianggu.
Swedish name: Ekmussling.
Mechanism of Action
Shiitake is very rich in essential amino acids, minerals, B vitamins and provitamin D2.
Also, it contains 1-3 beta-glucans; polysaccharide KS-2; glycoproteins (LEM, LAP); and eritadenine.
Other substances found in Shiitake include erythritol, copalic acid, adenosine, and carvacrol.
Two of the more active compounds are AHCC (Active Hexose Correlated Compound), and lentinan,
- AHCC (Active Hexose Correlated Compound): The glucan called AHCC (Active Hexose Correlated Compound) is widely used in the alternative and complementary treatment of cancer in Japan. This is due to its immune-enhancing functions. AHCC supplementation clearly affects immune outcomes and immune cell populations. This is especially true for natural killer cell activity.
- Lentinan: Lentinan (1,3 beta-D-glucan), a polysaccharide isolated from Shiitake, is thought to be responsible for many of the mushroom’s beneficial effects. Although it has been shown to have anticancer effects, lentinan is considered a biological response modifier, rather than having a direct cytotoxic effect on tumor cells.
The Shiitake mushroom (Lentinus edodes), have demonstrated antimicrobial, cytotoxic, anti-inflammatory, and antioxidant activity.
Studies conducted with Shiitake extracts in vitro and in animal models reveal immunostimulatory, antiviral, hepatoprotective, antihypercholemic, antiproliferative, cytotoxic, antimutagenic and anticaries properties.
Cancer and anti-tumor activity
Examples of results of studies:
Dried shiitake extract can cause apoptosis in human hepatocellular carcinoma (HepG2) cells by mediating caspase-3 and -8 pathways.
Inhibition of lung cancer cells by the Latcripin-13 domain isolated from Shiitake was shown to be due to apoptotic induction.
Anticancer effects of the polysaccharide lentinan (1,3 beta-D-glucan) may be due to its ability to suppress cytochrome P450 1A enzymes that are known to metabolize procarcinogens to active forms.
Polysaccharides SLNT1 and JLNT1 isolated from the mushroom demonstrated antitumor effects by increasing serum IL-2 levels and TNF-α production, and by inducing apoptosis in tumor cells in mice.
An orally administered Shiitake mycelial extract decreased the incidence of chemotherapy-associated adverse effects in a small study of patients with advanced gastrointestinal cancer.
Six week old ICR mice treated with N-butyl-N’-butanolnitrosoamine (BBN) received normal feed in the control group and 5% dried and powdered Shiitake in the experimental. 100% of the control group developed urinary bladder carcinoma (10/10) while the incidence was reduced to 52.9% in the experimental group (9/17).
The Shiitake enriched diet also increased the levels of macrophage activity and the mitogenic response of lymphocytes to concanavalin A (con A) to almost normal levels.
It also increased the cytotoxic activity of lymphokine-activated killer (LAK) cells and natural killer (NK) cells which were depressed by BBN treatment.
It indicates that Shiitake fruit bodies administered in the diet have anti-tumor activities in murine systems.
The anti-tumor effects of Shiitake feed murine systems has been paralleled by the anti-tumor effects of lentinan, which has been reported to prevent both chemical and viral carcinogenesis.
A 2006 study published in the Journal of Alternative and Complementary Medicine investigated the potential roles of an ethyl acetate fraction from shiitake mushrooms.
The study involved two human breast carcinoma cell lines, one human nonmalignant breast epithelial cell line and two myeloma cell lines.
The results suggest that shiitake mushrooms were able to inhibit growth in tumor cells with their mycochemical value.
Shiitake mushroom successfully inducted apoptosis, the process of programmed cell death.
Shiitake can either up-regulate or down-regulate the immune system.
Several studies have demonstrated this potential, with one set of studies showing they prevent overactivity of the immune system – helping to reduce inflammation and allergies.
Another set of studies showed that Shiitake can stimulate a poorly functioning immune system, helping to fight off viral infections – including tumor-related growths.
In April 2015, the University of Florida Institute of Food and Agricultural Sciences published a study showing increased immunity in persons who ate cooked shiitake mushrooms every day for 4 weeks.
Through blood tests before and after the experiment, researchers saw better-functioning gamma delta T-cells and reductions in inflammatory proteins.
Shiitake mushroom supplementation enhanced gut immunity by upregulating interleukin (IL)-23 secretion in a murine model of acute dextran sodium sulfate-colitis.In a randomized dietary intervention in young adults, eating Shiitake mushrooms for 4 weeks altered immune function.
Shiitake consumption in adults altered immune function via the increased proliferation of gamma delta-T and NK-T cells increased secretory immunoglobulin A in saliva, increased IL-1alpha, IL-4, IL-10, and tumor necrosis factor (TNF)-α levels, and decreased macrophage inflammatory protein-1alpha/chemokine C-C ligand 3 (MIP-1alpha/CCL3) levels.
Oral ingestion of whole mushroom extracts has shown to modulate certain immune functions, although the oral administration of the polysaccharide lentinan is less effective.
The differences in effectiveness between Shiitake and the lentinan extracted indicates that other constituents of the mushroom may have a bioactive role.
A 2015 study published in the Journal of the American College of Nutrition evaluated 52 healthy males and females, aged 21–41 years, to determine if Shiitake mushrooms could improve human immune function.
The study involved a four-week parallel-group trial that involved participants consuming either five or 10 grams of mushrooms daily.
The results suggest that consuming mushrooms improved cell effector function and improved gut immunity. There was also a reduction of inflammation due to mushroom consumption.
High cholesterol and Cardiovascular (CV) disease
Shiitake mushrooms contain three compounds that may help to lower cholesterol;
- Eritadenine – inhibits an enzyme involved in the production of cholesterol. Eritadenine may exert antihypercholemic effects and regulate lipid metabolism by inhibiting S-adenosyl homocysteine hydrolase activity, and both eritadenine and Shiitake mushroom supplementation upregulated CYP7A1 mRNA expression which was decreased in hypercholesterolemic mice. Researchers at Shizuoka University in Japan found that eritadenine supplementation significantly decreased plasma cholesterol concentration.
- Sterols – molecules that can help to block cholesterol absorption in the gut.
- Beta-Glucans – a soluble fiber which dissolves in the digestive tract and creates a thick gel-like paste, this binds with excess cholesterol to keep it from being absorbed.
Cardiovascular (CV) disease is the biggest cause of mortality worldwide and high blood cholesterol levels are an important risk factor in the development of CV problems, so any hypocholesterolemic effects are of great importance.
The ability of Shiitake to lower blood cholesterol was first reported in the 1960s. It was found that a diet supplemented with the dried ground sporophores lowered average plasma cholesterol when fed to rats.
The main active component was defined and named eritadenine. It supposedly lowers all lipid components of serum lipoproteins in both animals and humans.
Orally it was found to be effective ant have low toxicity although only 10% is absorbed from the intestinal tract.
Several other studies have supported these findings. For example, in spontaneously hypertensive rats dried Shiitake decreased both the VLDL and HDL cholesterol levels and therefore prevented blood pressure increase in hypertension, and inhuman testing, serum cholesterol was decreased in groups of women fed fresh, dried or UV-irradiated Shiitake.
Shiitake can also protect against atherosclerosis by reducing the production of immune cell adhesion molecules, which make cells sticky and cause plaques on the arteries.
A study conducted at Tohoku University in Japan found that Shiitake mushrooms prevented blood pressure increase in hypertensive rats.
Shiitake feeding resulted in a decrease in VLDL and HDL cholesterol, whereas Maitake mushroom feeding caused a decrease in VLDL cholesterol only.
Obesity, Weight Loss
Certain components of the Shiitake mushroom have hypolipidaemic (fat-reducing) effects, such as eritadenine and B-glucan.
Studies have reported that b-glucan can increase satiety, reduce food intake, delay nutrition absorption and reduce plasma lipid (fat) levels.
Shiitake is around 30% fiber which not only increases satiety, it is the kind of fiber that makes it difficult for the body to absorb fat.
In a study conducted by the University of Wollongong, Australia, a research group fed four groups of rats a high-fat diet along with a certain amount of shiitake supplements.
The rats that received the highest amount of Shiitake also had the lowest weight gain, around 1/3 less than rats fed the fatty diet without Shiitake.
These findings theorize that certain components in the mushrooms could increase fat elimination, reduce certain fatty acids, and/or inhibit the release of triacylglycerol from the liver.
A 2011 study published in the Journal of Obesity examined the effects of Shiitake mushrooms on plasma lipid profiles, fat dispositions, energy efficiency, and body fat index.
Rats were fed a high-fat diet for a six-week period. Researchers found significant effects of dietary intervention on body weight gain.
Rats on a high dose of Shiitake mushroom diet (which involved adding the mushroom powder to a high-fat diet) had 35 percent lower body weight gains than rats on low and medium shiitake mushroom diets.
Rats on the high dose shiitake mushroom diet also had significantly lower total fat masses and had a trend of lower fat accumulation.
The researchers concluded by suggesting that shiitake mushrooms can help prevent body weight gain, fat deposition, and plasma triacylglycerol when added to a high-fat diet.
This encourages an effort to pursue human studies that examine the efficacy of shiitake mushrooms for the prevention and treatment of obesity and related metabolic disorders.
Shiitake extracts are used as prebiotic agents and studying how this can help prevent obesity-related metabolic disorders.
High doses of Shiitake mushroom have been able to prevent obesity in rats by increasing plasma triacylglycerol accumulation in the liver.
Human Immunodeficiency Virus, HIV
The human immunodeficiency virus (HIV) has shown some sensitivity to Shiitake extracts in several experiments.
Lentinan in combination with 3’-azido-3’-deoxythymidine (AZT) suppressed the surface expression of HIV antigen more strongly than AZT alone in vitro. It was also shown to enhance the effect of AZT on the replication of HIV in various human hematopoietic cell lines in vitro.
In another study, several fractions of LEM (an aqueous extract of the Shiitake and its solid culture medium) caused inhibition of the infectivity and cytopathic effect of HIV.
Infection with HIV leads to acquired immune deficiency syndrome (AIDS). The CD4 molecule on helper T cells serves as a receptor for HIV infection.
The viral RNA is converted into DNA by the host reverse transcriptase and is incorporated into cellular DNA, this results in the insufficiency of cell-mediated immunity.
The immunomodulating effects of lentinan may be useful drug therapy for AIDS patients, although data on this idea is scarce.
Low-Molecular-Weight lignin from shiitake inhibits the hepatitis C virus by binding to viral apolipoprotein E (apoE) before interacting with cell surface heparan sulfate.
Polio and herpes
Shiitake extracts and the polysaccharide lentinan exerted antiviral effects, by acting on initial replication processes of poliovirus type 1 (PV-1) and bovine herpesvirus type 1 (BoHV-1).
A Japanese mushroom extract appears to be effective for the eradication of human papillomavirus (HPV), according to a pilot clinical trial.
Ten HPV-positive women were treated orally with the extract, AHCC (active hexose correlated compound) once daily for up to six months.
Five achieved a negative HPV test result — three with confirmed eradication after stopping AHCC – with the remaining two responders continuing on the study.
Other significant aspects of the immunomodulatory effects of shiitake are increased host resistance to bacterial and viral infections.
Lenthionine, a cyclic organosulfur compound (molecular formula C2H4S5) partly responsible for the flavor of shiitake mushrooms, has antibacterial and antifungal activity.Bis[ (methylsulfonyl)methyl] disulfide, a derivative of lenthionine, has strong inhibitory effects against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli.
The chloroform and ethylacetate extracts of the dried mushroom have bactericidal activity against both growing and resting Streptococcus mutans and Prevotella intermedia.
Only a few studies have explored antibacterial components of shiitake, and these have concentrated on their potential in terms of bacteria of oral origin.
Anti-bacterial activity is an exciting result, with increasing bacterial resistance to antibiotics, improving host immunity may be the way forward in fighting bacterial infection.
A postulated mechanism for the antibacterial activity of lentinan may be by the induction of increased levels of complement C3 and C3b formation.
Although, modulation of the non-specific immune system has also been displayed in numerous studies, and may be the potentiator of the anti-bacterial activity of lentinan.
Many immunomodulatory effects have been reported, including an increase of monocyte function in terms of IL-1 production.
Inhibition of circulating tumor necrosis factor-α (TNFα) and increases in the expression of cytokines: analysis of the cytokine expression profile after lentinan administration revealed a marked increase in the mRNA levels of IL-1a, IL-1b, TNF-a, IFN-g and M-CSF in the peritoneal exudate cells and splenocytes.
Another polysaccharide isolated from Shiitake exhibited antibacterial effects in mice by increasing T-helper (Th1) cell immunity, resulting in activation of a macrophage-mediated immune response.
The isolated protein lentin exhibited antifungal properties, inhibited proliferation of leukemic cells, and suppressed the activity of human immunodeficiency virus-1 (HIV-1) reverse transcriptase.
Cytotoxic properties were evaluated against 3 cell lines (HepG2, HeLa, PaTu), whereas the anti-inflammatory activity of tested samples was assayed based on their ability to attenuate the secretion of the cytokine tumor necrosis factor-α.
Antioxidant activity was measured using in vitro DPPH and ABTS assays.
It was found that lenthionine possesses significant antimicrobial properties; it is remarkably effective in inhibiting the growth of yeasts and fungi (minimum inhibitory concentration, 2-8 μg/mL) and thus is comparable to standard antifungal agents.
Lenthionine is also able to decrease significantly the production of tumor necrosis factor-a and thus could be at least partly responsible for the observed anti-inflammatory effect of shiitake.
On the other hand, lenthionine does not seem to contribute significantly to the well-known anticancer and antioxidant effects of the mushroom.
Indigenous to Japan, China and Korea, Shiitake has a long history of cultivation, with one of the first historical records to mention shiitake dated 199 AD.
In China, the cultivation of Shiitake started around 1,000 years ago with a man called Wu San-Kwung.
According to legend, Kwung was testing his axe on a log that had shiitake growing on it – swinging his axe he made several cuts in the log before leaving.
He returned some days later to discover that more shiitake had grown exactly where the log had been chopped by his axe.
Kwung continued to successfully experiment, becoming the pioneer of cultivated shiitake.
In his quest to perfect his method of cultivation he became frustrated with one particular log that wouldn’t fruit.
After a long, hard, rainy day Kwung vented his frustration by beating and flinging the log around.
Upon his return he discovered that the log he had beaten so vigorously was completely covered in mushrooms.
Kwung had inadvertently discovered the ‘soak and beat’ method of mushroom cultivation which is still in use today.
Kwung’s contribution to Shiitake cultivation is commemorated in a temple situated in Qingyuan, where festivals are still celebrated in his name.
In traditional use, Shiitake is known in the following areas:
- Activation of the immune system in case of bacterial and viral infection.
- Cholesterol and blood pressure regulation.
- Antiartheriosclerotic effect.
- Support for bowel cleansing.
- Mitigation of osteoporosis and rheumatic diseases.
- Complementary therapy of tumors and tumor prevention.
Possibly the most popular mushroom in the world after the button mushroom, Shiitake has long been a favorite of the Chinese and Japanese.
Traditional Chinese Medicine (TCM) uses this mycelium heavyweight as a stimulant to boost overall health, prevent strokes, relieve hunger, strengthen the immune system, stimulate “qi” (life force) and improve circulation.
Most of these properties were pioneered by the Chinese in the “Ri Youg Ben Cao”, a Traditional Chinese Medicine compendium written in 1620.
Traditional Chinese Medicine
Application fields in Traditional Chinese Medicine
- Replenishes Qi and nourishes the blood.
- Dissolves humidity and mucus.
Spleen, stomach, lungs.
- Boosting the immune system,
- Lowering blood cholesterol levels,
- Hardening of the arteries,
- Diabetes, Eczema,
- Colds and flu,
- Treating prostate or breast cancer,
- Anti-aging agent,
- Hepatitis B,
- High blood pressure, and
- Stomach ache.
500 mg up to 2 grams of extract. 3 to 6 grams of Shiitake powder.
Health problems, acute use
1,5 grams to 5 grams of extract.
- Intake of Vitamin C may increase the absorption of active substances.
- Use 5 out of 7 days each week.
- Recommendations for medical mushrooms have a wide span ranging from a few hundred milligrams up to many grams a day. Historically, a huge variation of preparations, powders, and strengths of extracts has been used. Sometimes, it can be difficult to compare different products and recommendations.
Side Effects & Safety
Intake of Shiitake has been linked to the following side effects:
- Skin inflammation.
- Increased skin sensitivity to sunlight.
- Abnormally high level of certain white blood cells.
- Upset stomach.
- Pneumonia caused by hypersensitivity to spores.
- Small bowel obstruction from eating a whole shiitake mushroom.
Hypersensitivity pneumonitis: In a lung cancer patient following exposure to shiitake spores, and in a 37-year-old man following inhalation of shiitake mushroom spores.Dermatitis, photosensitivity, eosinophilia, and gastrointestinal upset: Following prolonged consumption of shiitake powder.Shiitake dermatitis, flagellate erythema: Patterns of whiplike, linear, erythematous wheals after consumption of raw or even cooked shiitake mushrooms which has been associated with toxic reactions to the constituent lentinan.Intermittent dermatitis over a 16-year period: Linked to the consumption of shiitake mushrooms in a 45-year-old male.Esophageal symptoms: Linked to a food allergy in a 37-year-old man following consumption of shiitake mushroom.Small bowel obstruction: Caused by ingestion of a whole shiitake mushroom, resulting in necrosis and mucosal damage in the small intestine.
Chronic consumption of shiitake may increase eosinophil count.
Background and taxonomy
Shiitake, the common Japanese name for the edible mushroom Lentinula edodes, which is cultivated and is the second most commonly produced edible mushroom in the world.It grows naturally on fallen wood of broadleaf forests and according to a Chinese physician of the Ming Dynasty (1368-1644), Wu Juei, it preserves health, improves stamina and circulation, cures colds and lowers blood cholesterol.Cultivation, and especially the use of this mushroom for healing purposes in Asia, especially in China and Japan, has a very long, literally thousand-year tradition. Japanese writings from 199 AD describe how the Kyusuys, a Japanese tribe, brought Shiitake as a gift to the Japanese emperor.Shiitake is also referred to as an elixir of life in the historical writings of traditional Chinese medicine. Texts from the Sung Dynasty (960-1127) even speak of the beginnings of cultivation and purposeful growth of this mushroom.Another text written by Wang Cheng in 1313 specifies the technique of cultivation.It was first described and classified for the Western world in 1877 by M. J. Berkeley, who named it Agaricus edodes.This name for Shiitake lasted until 1976, when it was assigned by D. Pegler to the genus Lentinula.Nowadays, the mushroom is commercially grown around the world.
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