Shiitake is a great addition to any diet, not in the least to vegans and vegetarians, as they have a great nutritional profile, being low in fat and rich in protein, fibre, vitamins and minerals. Notably, they have high levels of B vitamins and vitamin D2, supporting adrenal and cognitive function, bone and heart health. They are also one of the richest dietary sources of copper, an essential nutrient involved in red blood cell formation, bone health, cardiovascular, immune and nervous system functioning as well as collagen production.  

Like many medicinal fungi, shiitake extracts have been widely studied and applied to cancer care for decades not only to promote cancer cell death and inhibit their proliferation but also as an adjuvant to enhance the efficacy of conventional therapies, reduce side effects and support the immune system, thereby potentially reducing recurrence (1).  

Indeed, immune support is another of shiitake’s primary health benefits. Observed immunomodulatory effects alongside antiviral and antimicrobial properties make shiitake tasty little immune powerhouses that are easily incorporated into one’s daily life with potential benefits for sufferers of conditions such as HIV, candida and hepatitis to name but a few (2).    

They have also displayed an ability to influence the gut microbiota, blood lipid levels and blood pressure and may, therefore, also be a useful dietary and herbal allay for those suffering with poor digestion, high cholesterol and hypertension. 

Rich in polysaccharides (even as compared to other edible mushrooms (2)) and beneficial bioactive compounds, shiitake has been studied extensively, particularly in relation to its perceived anti-cancer and immune-modulating abilities. Indeed, Lentinan, a polysaccharide extract from shiitake mycelium, was the earliest and most thoroughly studied of all the edible fungi polysaccharides and has been used clinically as an anticancer adjuvant therapy in Japan and China since the 1980s (4). 

In traditional East Asian medicine, shiitake is regarded as energetically sweet and neutral making it a gentle, nourishing tonic for the body that lend itself to regular consumption and has been used in traditional East Asian medicine for thousands of years to strengthen weakness, in particular of the Spleen and Stomach; our digestive centre. In doing so, they not only help to address digestive deficiencies manifesting in symptoms such as poor appetite and bloating, but also promote the flourishing of our qi (energy), blood and wei qi (immunity) whose vigour is firmly rooted in sound digestion.

Lentinula edodes, known in Japan and more widely as shiitake (shii meaning the Castanopsis cuspidata tree and take meaning mushroom) and ‘fragrant mushroom’ (xiang gu) in China has an extensive history in East Asia where it has been used in food and traditional medicine as a qi tonic to bolster strength, digestion, circulation and immunity for millennia. Many traditional sources also hold that shiitake supports fluid metabolism, reducing dampness and phlegm in the body.

The following are the main extracts and bioactive compounds of shiitake:

Lentinan

A polysaccharide extract derived from shiitake mycelia. Beta-glucans are its major active component and it is known for its immunostimulatory and antineoplastic (anti-cancer) effects. It is licensed for clinical use for treating stomach cancer in Japan and has been used as a chemotherapy adjuvant therapy in China and Japan for decades. Lentinan is also used in the treatment of viruses such as HIV and hepatitis. 

LEM (Lentinula edodes mycelia extract): a shiitake mycelia crude, hot water extracted powder with potential immunomodulatory and antitumor properties. 

AHCC (active hexose-correlated compound): a proprietary alpha-glucan extract from sources including shiitake mycelia and a popular supplement for cancer patients in Japan since 1987, AHCC is also taken for the treatment of HIV, HPV and impaired liver function.  

Eritadenine

A chemical compound from shiitake fruiting bodies and mycelia with demonstrated lipid-lowering effects, it has been found to inhibit an enzyme involved in cholesterol production. 

Ergothioneine

An amino acid derived from a small selection of natural sources including shiitake, with powerful antioxidant properties. 

In addition to the regular consumption of the shiitake mushroom fruiting body, the following potential benefits (elucidated from just some of the many existing pre-clinical and clinical studies – some of which small and need further exploration) were gained from the above extracts and compounds (see Research below for individual study details).

Cancer

Shiitake displays an ability to inhibit the proliferation of tumour cells (5,6) and induce cancer cell apoptosis (cell death) (5). When given alongside chemotherapy it may enhance its effects, (7) improve quality of life, (8,1) increase immune function, (1,7,8) reduce neutrophil-related side effects (where low white blood cell counts are a common side-effect of chemotherapy) and the resultant use of Granulocyte-colony stimulating factor (G-CSF) (the typical treatment for neutropenia, that comes with its own side effects) (9).

Immune

Shiitake has been seen to increase immune function generally. (1,7,8,10) In particular, it may increase T-cell (including Natural Killer cell (NKC)) numbers and activity, (8,10,11) influence the function of innate immune cells such as monocytes, macrophages and DCs (dendritic cells; messenger cells between the innate and adaptive immune systems), (12) alter cytokine (immune messenger protein) expression, lower inflammation levels, increase secretory IgA (SIgA) (the primary antibodies found in the gut) and, therefore, intestinal immunity (11) and increase IFN-y (an important cytokine involved in activating immune responses) (13). 

Other

Shiitake may also reduce blood pressure (14) and triglycerides (blood lipids), (14-16) inhibit weight gain, (16) reduce oxidative stress biomarkers and increase the body’s main endogenous (self-made) antioxidant, (15) influence gut microbiota, (17) exhibit selective antibacterial effects (18) and possess antiviral effects (19).

Cancer

When treating chronic, complex or serious conditions it is always best to approach a qualified integrative healthcare practitioner/ specialist. There are many nuances when working with herbs and serious conditions and sometimes one can unwittingly exacerbate issues. A qualified herbalist and integrative practitioner will be able to discern and guide you safely. You can learn more about herbal approaches for caring for cancer in our podcast with herbal oncologist Chanchal Cabrera.  Also, take a look at our resource page “Where to find a herbalist” and see our article Mushrooms for cancer care.

In vitro studies

An early study using an ethyl acetate fraction of shiitake with human breast and blood cancer cell lines found that the fraction not only inhibited the proliferation of tumour cells but also induced apoptosis (cell death), suggesting possible anti-tumour capabilities (5).

A subsequent study using aqueous extracts of both shiitake fruiting body and mycelium with human breast cancer cell lines also observed a direct and significant antiproliferative effect (6). 

Human clinical trials

A very small study of 7 breast or gastrointestinal cancer patients receiving chemotherapy post-surgery found that LEM (Lentinula edodes mycelia extract) alongside chemotherapy produced no adverse events, improved quality of life scores, natural killer cell activity and immune function as compared to a prior round of chemotherapy where they received chemotherapy alone (8).

A larger retrospective study of 41 women receiving chemotherapy for breast cancer found that 3g of AHCC (active hexose-correlated compound) daily resulted in significantly less neutrophil-related side effects from chemotherapy as compared to the control group and, subsequently, a reduction in the use of Granulocyte-colony stimulating factor (G-CSF). Neutropenia (low white blood cell count) is a common side effect of chemotherapy and G-CSF is the typical treatment for this but carries with it its own side effects. (9)   

A 2017 placebo-controlled randomised double-blind study of 47 women with early-stage breast cancer receiving postoperative anthracycline-based chemotherapy gave 1800mg LEM in tablet form per day alongside 5HT3 receptor antagonists (commonly prescribed as supportive therapy to alleviate chemotherapy-induced nausea and vomiting) to the experimental group for the duration of two courses (6 weeks) of chemotherapy. The placebo group, receiving no LEM, recorded decreased quality of life and lowered immune function. Those receiving LEM adjuvantly reported no reduction in quality of life and immune function was maintained. (8)

A similar study involving 50 oesophageal cancer patients examined the use of 1mg diluted Lentinan per day alongside chemotherapy. After two rounds of chemotherapy, clinical efficacy (remission versus progression) was significantly greater in the experimental group along with a relative increase in immune function. Both groups showed an improvement in general condition, signs and symptoms and quality of life scores after the two rounds of treatment, however improvement was significantly greater in the group receiving LEM (7).   

Immunity

Reviews

A 2019 review of 20 clinical and pre-clinical studies concluded that AHCC has numerous immunologic effects, in particular on T-cells and natural killer (NK) cells whose function and numbers may be influenced by the compound. It is also believed to influence the function of innate immune cells such as monocytes, macrophages and DCs (dendritic cells; messenger cells between the innate and adaptive immune systems), again promoting T cell function, with promising biological effects on tumours, inflammation and infections. (10)    

A subsequent, 2022 review of clinical and pre-clinical studies exploring the immunomodulatory effects of shiitake also concluded that, from the 12 human trials reviewed, shiitake polysaccharides appear to have a strong immunologic influence on humans, however the nature of these effects seems to differ according to the extraction method used and the source (fruiting body or mycelium) with Lentinan (extracted from the fruiting body) being immunostimulatory and polysaccharides derived from the mycelium yielding selective immunosuppressive effects (20).

Human clinical trials

A parallel group study involving 52 healthy participants consuming 5 or 10g of whole dried shiitake mushrooms daily for four weeks found that shiitake consumption both increased specific T-cells (Gamma-delta and Natural Killer) and their function, significantly altered cytokine (immune messenger protein) expression and lowered inflammation levels and increased secretory IgA (SIgA) (the primary antibodies found in the gut) and, therefore, intestinal immunity (11).

A randomised, double-blind, placebo-controlled trial involving 80 healthy participants explored the immune effects of daily consumption of 18g of rice bran fermented with shiitake (rice bran exo-biopolymer (RBEP)) in capsule form over eight weeks. They found RBEP supplementation increased IFN-y (an important cytokine involved in activating immune responses) secretion with no adverse effects. (13)

A smaller randomised control trial (RCT) looking in to the effects of 3g per day of AHCC on DCs (dendritic cells) in 21 healthy participants over four weeks found a significant increase in DCs in the experimental group as compared to baseline and the control group along with an increase in function of DC1s (dendritic cells involved in acquired immunity). (12)

Obesity / Cholesterol / Hypertension

A 2021 double-blind RCT involving 68 participants with borderline high cholesterol investigated the effects of daily consumption of a shiitake food bar for 66 days, at the end of which the intervention group showed a 10% reduction in triglycerides (blood lipids) and improved oxidative stress biomarkers including an increase in the body’s main endogenous antioxidant. (15)

Similarly, animal studies using shiitake fruiting body powder displayed beneficial effects on blood lipid levels (14,16), weight gain (16) and hypertension. (14)  

Gut health / Cholesterol

A 2021 double-blind RCT involving 52 participants with high cholesterol explored the cholesterol-lowering and immune and gut microbiota modulating effects of a shiitake-derived beta-D-glucan-enriched mixture where 3.5g of beta-D-glucans were consumed daily over eight weeks. It was found that the mixture altered the colonic microbiota of the test subjects with several types of microbial organisms affected being directly linked (positively and negatively) with some of the biomarkers associated with the metabolism of cholesterol (17).

Antimicrobial

An in vitro study using human saliva investigating the antimicrobial effects of a shiitake extract on gingivitis (gum inflammation) as compared to the leading gingivitis mouthwash established that not only did the shiitake extract lower bacterial numbers but it did so without impacting the microbial species associated with oral health in contrast to the mouthwash which lowered numbers of all bacteria, both good and bad (18).

Another in vitro study exploring the antiviral effects of both aqueous and ethanol extracts of shiitake fruiting body as well as shiitake polysaccharide (LeP) from the fruiting body found they all inhibited the replication of poliovirus type 1 and bovine herpes virus type 1 in the early stages of infection (19).

Reverence of the shiitake mushroom in China is such that an annual day of feasting celebrates the life of Wu San Kwung, believed to be the first to cultivate this coveted mushroom in around 1000CE, with temples across the country also dedicated to his memory (21).

Grows in the wild in East Asia in warm, humid environments on a range of fallen deciduous hardwood trees. Cultivated globally.

The International Union for Conservation of Nature (IUCN) Red List of Threatened Species does not feature the shiitake mushroom. Issues around shiitake sustainability appear to be from the sheer enormity of the scale of its cultivation globally and the potential energy consumption and waste that artificial commercial production inevitably produces:

“In the author’s experience, for every 900 g of shiitake mushroom yield, ~15 g of HDPE bags [non-biodegradable, disposable high-density polyethylene bags] become waste. This means that if the global production of shiitake mushroom is 10 million tons based on past literature [from 2017], then more than 160,000 tons of waste is produced annually.” (23 p5)

Chinese shiitake log cultivation is a more eco-friendly means of production, however, the sustainable sourcing of these trees must also be considered. “Forest farming” shiitake is another ecological alternative and is already extensive in Japan (23).

Look for supplements with high levels of polysaccharides, ideally a minimum of 15% beta-glucans, and without fillers or starches.

Best grown on sawdust pellets or deciduous hardwood logs (especially oak) in the spring. Logs inoculated with plug spawns (inoculated wooden dowels) are an easy option for beginners with great yield potential. Hammer plugs in to holes drilled in clean, relatively freshly cut logs then cover with wax. Place in a shady position, raised from the ground and water weekly or bi-weekly if in a dry climate. Incubation takes between 6-12 months. After this time, submerge the log in water for 24 hours then stand in the shade. Mushrooms will begin to grow within 2 weeks and logs must be watered daily. Logs may last between 4-6 years with forced flushes of mushrooms every 5-6 weeks after repeating the soaking process (24).

This delicious mushroom broth recipe shares how to make a delicious shiitake soup which incorporates other medicinal herbs.

Ingredients:

• 3 strips small kombu
• 2 sage leafs
• 2 dried shiitake mushrooms
• 1⁄4 tsp sesame oil
• 1.5l water
• 1 tsp tamari
• 1 clove of garlic
• 1 tsp ginger, grated
• Pinch of pepper

Method:

1. Soak the shitake mushroom in 1.5l of water for at least an hour or until the inside is fully rehydrated.
2. Keep the soaking water for cooking. Add tamari and a pinch of pepper. Stir well.
3. In a pot, add the shitake water the shiitake was soaked in, kombu, shitake mushrooms, grated garlic and ginger,
4. Turn the heat on high and bring to a boil, then turn down the heat to simmer for about 20 mins.
5. Slice the kombu thinly into strips when it is soft and cooked through, then put it back in the soup.
6. Turn the heat off.
7. Finely slice the sage leaves into small strips and add them on top of the soup as a garnish.
8. Let it infuse for 10 minutes.
9. Serve.

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