Perhaps the most unexpected active ingredient in our centess+complex range is Lentinus edodes– or better known as the shiitake mushroom. The worlds’ second most widely consumed mushroom,1 the shiitake is one of an array of ‘medicinal mushrooms’ used in traditional medicinal practices and increasingly entering the Western culinary market due to their health-promoting nutritional qualities when compared with the dominant button mushroom.
Let’s find out why mushrooms could be the next big thing in naturally effective skincare.
Introducing Lentinus edodes
For centuries, shiitake mushrooms were reserved for Japanese royalty earning itself the name the ‘monarch of the mushrooms’ thanks to its superior taste and quality fit for kings.2 Given its original scientific name Lentinus edodes (L. edodes) by British botanist Miles Joseph Berkley in 1877 it’s now known taxonomically as Lentinula edodes where the digestible nature of the mushroom is denoted by ‘edodes‘- the Latin word for edible. Though shiitake have been heralded as a cure-all medicinal mushroom by traditional Eastern medicine practices we are only just beginning to scratch the surface of its capabilities as a naturally effective ingredient in skincare.
The dietary value of shiitake alone makes these mushrooms of great interest as a functional food- that is a food that provides benefits to human health in addition to its nutritional profile. They’re a great source of protein, complex carbohydrates and minerals such as potassium, iron and zinc.3 However, they have also been shown to modulate the immune system, demonstrating efficacy against a number of diseases with some shiitake-derived bioactive compounds being used as pharmaceutical grade products in the Far East. This is an area of considerable interest to scientists globally as they attempt to unravel the biochemistry and mechanisms of action behind the countless therapeutic potentials of shiitake suggested by centuries of folkloric medicine and translating them into modern medicinal uses.
Traditional uses of Lentinus edodes
The medicinal properties of L. edodes have been studied since the Ming Dynasty (1369-1644). It’s reported that Japanese Empire elders regarded shiitake as the ‘elixir of life’ with reviving properties that increased energy and vigour.1 In folklore shiitake have been used in the treatment of heart disease, tumours, diabetes, respiratory disease and sexual dysfunction. They were even administered for flu, exhaustion and weakness.
Although many cultures have utilised mushrooms both as a food and as a medicine, the most extensive and notable use of mushrooms as a functional food can be found in the East where their use in traditional Chinese medicine is recorded as early as 100AD.
Administered as a tea, tonic or tincture, shiitake were used in preparation of soups and herbal formulas to impart their nutritional and therapeutic benefits.4 Traditional Chinese medicinal practice saw shiitake prescribed for invigorating the spleen, kidney function and in easing respiratory function. Other cultures making use of medicinal mushrooms in complementary medicinal practice are Korea, Japan and Eastern Russia- notably areas where shiitake are indigenous.5
General Health Benefits and Uses
An age-old folk remedy for illness ranging from the common cold to easing inflammatory conditions, research studies are building a good body of scientific evidence that support the wide-ranging medicinal uses of shiitake reported by traditional medicine, with scientists beginning to understand the compounds and mechanisms of action responsible for making shiitake so naturally bioactive.
L. edodes posesses an impressive array of properties1,6 with some more deeply studied and understood than others- but showing great promise in providing naturally effective therapeutic products that are:
Anti-inflammatory & Immunomodulating with some evidence of enhancement of immune function in immunosuppressed patients8
Anti-viral/Anti-microbial metabolites from shiitake display anti-microbial action against both gram-positive and gram-negative bacteria9
Anti-hyaluronidase shiitake extract has been reported to maintain hyaluronidase levels, helping ageing skin repair and rejuvenate itself6
Mushrooms have attracted increased attention in recent years thanks to their highly potent bioactivity profile. With further human trials and clinical evidence to support early work, shiitake extract could be developed into medicines for the prevention and treatment of several chronic diseases such as cancer, cardiovascular disease, diabetes as well as neurodegenerative diseases.10
The ability of mushrooms to modulate immune function can be attributed to the compounds in their extensive bioactive profile including polysaccharides, proteins, polyphenols and terpene compounds. In the Far East the shiitake mushroom is used therapeutically for diseases involving suppressed immune systems (including AIDs), a variety of cancers, allergies, bronchial infection and even simply in preventing the common cold and flu.
Japanese research trialling the adjuvant use of shiitake extract in combination with chemotherapy and radiotherapy has shown some initial promise and sparked significant interest in the medicinal effects of shiitake. With the current decline in the number of new agents successfully developed by the pharmaceutical industry, novel anti-cancer agents are being sought from traditional medicine. Further randomised, larger controlled studies are required to identify appropriate dosages and therapeutic methods and to confirm the beneficial effects seen in initial Eastern studies. The potential of shiitake in a variety of areas of applied biotechnology is undoubtable, however standard protocols are not yet in place to verify the quality and efficacy of the pharmaceutical grade extract.
Whilst immunomodulatory and anti-cancer activities have been the major therapeutic applications of medicinal mushroom derived compounds to date, other medicinal properties of mushroom extracts studied include the treatment of hypercholesterolemia, diabetes, high blood pressure as well as its anti-microbial and anti-oxidant activities. Shiitake extracts also show significant promise in the prevention of cardiovascular disease through its ability to reduce high cholesterol, and investigations continue in understanding its role in hypertension, immune system support, and parasitic and respiratory infections.
Mushroom extracts have also been researched as cosmetic ingredients, with mushroom metabolites identified as ingredients that could be used to target ageing processes, reduce symptoms of inflammatory skin conditions and address hyperpigmentation or dark patches on the skin.11 Compounds in shiitake have also been identified as bioactives potently effective in maintaining the structure and function of the skin by targeting anti-hyaluronidase enzymes that degenerate hyaluronidase, a compound which helps maintain moisture in the skin and leaves tissues less prone to oxidative stress.6 Further topical skincare research is required to identify the effective dosage and the full spectrum of skin-beneficial properties that shiitake and other medicinal mushrooms can afford us.
Botany and Cook it Yourself
Shiitake has a medium-sized, umbrella-shaped cap which can be from tan to brown in colour.12 The cap may be thick and fleshy or thin and vary in texture (they may be smooth or have a cracked appearance). The underside of the cap and the stem are white.
You may find shiitake mushrooms growing in groups on the decaying wood of deciduous trees such as chestnut, oak, maple and poplar.1
Indigenous to the warm and moist climates of Southeast Asia, L. edodes can be found growing wild in mountainous regions of China, Japan, Taiwan and Indonesia. The geographic range of wild shiitake now extends as far as New Zealand in the south and as far west as the Himalayan regions of Nepal, India and Bhutan. Examination of historical wind patterns and native L. edodes populations show that shiitake spores were carried in air streams and tornadoes westward and spread the fungi across East Asia.
Now cultivated all over the world, shiitake contributes 25% to the yearly production of mushrooms, with commercially grown mushrooms nurtured in conditions similar to their natural habitat on hardwood logs such as oak. Until 1982 the Japanese variant of shiitake could only be grown in traditional locations and using ancient growing methods, however after this time commercial cultivation opportunities began the Western love affair with this fantastic functional food. It is possible to grow your own at home13 with kits available to buy from specialist garden suppliers, and growing advice available from mycological societies.
Cultivation has been necessary in order to keep up with global demand for shiitake, however this can result in different physiological and biochemical conditions for shiitake growth. This means that the quality and content of bioactive compounds in L. edodes varies depending on the location, culture conditions and growth of the mushrooms, and as such the biochemical profile will vary from strain to strain. Genetic engineering may be able to provide more consistency in growth of the species globally and in developing a shiitake strain with uniform bioactive substrate profiles.
Cook it Yourself
Fresh and dried shiitake have a variety of culinary uses, particularly in the cuisines of Eastern Asia. Popularly served in miso soup in Japan or sautéed in Chinese vegetarian dishes and stir fries, the earthy, smoky flavour adds depth to dishes and is not only tasty but beneficial to your health. Being so high in protein content shiitake and other edible mushrooms are commonly used to supplement protein intake in countries with high malnutrition rates and could be used regularly to increase protein levels in an otherwise balanced diet. Shiitake are also important sources of essential amino acids, fibre, vitamins and minerals. It’s interesting to note that the drying process can affect the anti-oxidant levels present in dried shiitake, as the drying process can alter the chemical constituents and therefore the bioactivity profile of the mushroom.14
For all the goodness they provide, in rare cases, shiitake can cause a skin reaction caused by consuming raw or undercooked shiitake. Symptoms include small, raised red bumps on the skin (papules), severe itching and psoriasis-like skin plaques. Eating or handling raw or undercooked shiitake may produce these symptoms of allergic contact dermatitis in some people. Please consult your doctor if you develop these symptoms or before incorporating large quantities of shiitake into your diet.
Bioactivity and associated components of the plant
Recent advances in biochemical techniques have allowed the partial isolation and identification of active compounds extracted from shiitake. In addition to shiitake’s impressive nutritional profile, these mushrooms also offer medicinally effective compounds such as polysaccharides, terpenoids, sterols and fatty lipids. These compounds display impressive activity against several human disorders and diseases, mainly centred around their ability to positively modulate the immune system. 3 Most of the shiitake bioactives appear to act as non-specific immuno-stimulants, though some have been shown to have direct cytotoxic (anti-cancer) effects. A small number of the bioactives that have displayed significant therapeutic potential have progressed to clinical trials and are licensed as cancer treatments in the Far East.
Much of shiitake’s bioactivity can be attributed to its array of polysaccharides- complex carbohydrates made up of many single sugar units (poly meaning many and saccharide = sugar). The most investigated compounds derived from shiitake, polysaccharides provide a staggering portfolio of potential therapeutic applications, amongst which are their ability activate immune responses and its anti-tumour activities. Two polysaccharides, in particular, have been well-studied and have even been approved for clinical use in some countries as a medicine: lentinan (see our Spotlight for more background on this highly bioactive compound) and L. edodes mycelia (or LEM for short).
LEM is a protein-bound polysaccharide isolated from shiitake mycelium, which is the vegetative part of the fungus that forms very fine white filaments. Both LEM and lentinan have both been shown to work by enhancing various immune system functions rather than directly affecting tumour cells (or viruses in the case of viral infections).9 Viral diseases like human immuno-deficiency virus (HIV) are difficult to treat with modern pharmaceuticals and as such the strong inhibitory action of LEM in particular against a number of viruses is of great interest. 16
A number of shiitake polysaccharides exhibit anti-cancer activity, and differ greatly in chemical composition and properties. Polysaccharides isolated from different strains of the L. edodes species may display unique compositions and configurations, and as such may adopt different mechanisms of action to polysaccharides isolated from a different strain. Studies have so far identified that the potency of each polysaccharide is linked to its molecular size and complexity and how soluble it is in water. With the scientific data already collated and further studies, it could be possible to optimise or synthesise polysaccharides to confirm and increase their degree of efficacy in cancer treatment. So far, research has shown the wide array of bioactive polysaccharides to operate via multiple mechanisms of action against cancer, making these compounds of real interest for drug development as treatments for numerous different cancers.
Lentinan: a spotlight on the superstar polysaccharide
One of the pharmaceutically active compounds of great interest to scientists- and already being used clinically in Japan- is the shiitake-derived compound lentinan. Perhaps the most intruiging aspect of lentinan use in conjunction with cancer treatment is its apparent ability to improve the quality of life parameters in patients- for example reducing nausea, pain and hair loss. Studies show lentinan to be active against a range of cancers as well as to reduce the symptoms of treatment-related toxicity associated with chemo- and radiotherapy.
Lentinan has been approved for clinical use in Japan since the 1980s, and is currently used as an adjuvant treatment for certain cancers in China and Japan. In randomised, controlled studies lentinan has been reported to increase the survival of patients with advanced gastric17 and colorectal carcinomas in comparison to standard Japanese chemotherapy regimens. Mushroom extract has also demonstrated the ability to inhibit the proliferation of breast cancer cells although further studies are required to confirm these clinical outcomes. Lentinan has also shown significant efficacy in suppressing HIV-1 transcriptase when used in combination with HIV anti-retroviral drug AZT.
Further clinical research is required to understand lentinan’s role as an adjuvant treatment for various cancers and diseases and to fully maximise it’s potential as a therapeutic agent. Western clinicians are working to understand the science behind the Eastern traditional medicine and its developing the corresponding clinical therapies to optimally utilise lentinan and other bioactives as pharmaceutical solutions from nature.
Several mushroom polysaccharides have reached human clinical trials in cancer patients, with lentinan, schizophyllan, PSK and PSP the most studied amongst others. Another example of pharmaceutical successes derived from shiitake can be found in schizophyllan which has been reported to increase the survival of patients with advanced head and neck cancer. Much more research needs to be done to understand the huge number of factors surrounding these compounds’ ability to enhance or suppress the immune system including dosage, route and regime for administration and understanding in better detail their mechanism of action.
L. edodes also contains other bioactive polysaccharides that are of significant interest to scientists. Compound eritadenine plays an active part in reducing cholesterol levels, and since there’s a strong correlation between raised cholesterol levels and risk of cardiovascular disease there is interest in developing eritadenine as a preventative and therapeutic medicine. Polysaccharides are also credited as the source of shiitake’s potent anti-oxidant activity, including scavenging free radicals implicated in skin ageing processes and preventing the oxidation of lipids.6
A number of investigations report that compounds isolated from mushrooms such as polysaccharides, terpenes and phenolic compounds are most responsible for mushroom extracts’ anti-inflammatory potential. Their ability to reduce the production of inflammatory mediators by down-regulating immune functions means they are of relevance in clinical development of treatments for a whole host of inflammatory diseases.
Conventional cancer treatments like chemo- and radiotherapy have significantly adverse effects on the immune system. Cancer cells are also adept at surviving in human bodies with immune systems weakened by the illness, and as such can proliferate and spread throughout the body easily. With a disease and therapies that are immuno-suppresive, scientists are working to identify potent and affordable medicines that can be used alongside conventional treatment to increase treatment success and reduce the unpleasant side effects.
The human immune system uses two types of immunity to fight disease; cellular immunity and humoral immunity. Both these types of immunity use different mechanisms as immune surveillance for detecting antigens or foreign substances that shouldn’t be there. Although the exact mechanism of action of shiitake polysaccharides is still to be defined, early research suggests that these compounds can help regulate the immune system by assisting both the cellular and humoral immune processes. This gives these polysaccharides double potency in assisting the immune system identifying and killing cancer cells and stalling tumour growth. This ability to function in both immune processes is a likely explanation for the impressive and wide activity of polysaccharides against a multitude of different types of cancers, viruses (like HIV), bacteria (such as tuberculosis) and parasites. Immunostimulating agents could prove useful adjuncts to conventional cancer treatment and immunotherapy providing it doesn’t interfere with the efficacy of the standard treatments.
The diverse and vast potential therapeutic uses of L. edodes for the treatment of a variety of diseases including AIDS/HIV, cancer and hepatitis show shiitake has a bright future as a natural bioactive therapeutic agent. There seems to be no end to the potential applications of L. edodes‘ medicinally significant and naturally beneficial bioactives.
If you’re interested in reading more deeply on the multi-faceted bioactivity of Lentinus edodes why not check out some of the studies referenced throughout the article or why not find out more about some of the other naturally effective griffin+row ingredients in our active ingredient series?
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14. Oliveira, SM et al, Influence of drying processes and pretreatments on nutritional and bioactive characteristics of dried vegetables: a review, Food Eng. Rev., doi:10.1007/s12393-015-9124-0, 2015.↩
15. Stephany, MP et al, Shiitake mushroom dermatitis: a review, Am. J. Clin. Dermatol., 7, 5, 485-489, 2016.↩
16. Yamamoto, Y et al, Immunopotentiating activity of the water soluble Lignin rich fraction prepared from LEM- the extract of the solid culture medium of Lentinus edodes mycelia, Biosci. Biotech. Biochem., 61, 11, 1909-1912, 1997. ↩
17. Nakano, H et al, A multi-institutional prospective study of lentinan in advanced gastric cancer patients with unresectable and recurrent diseases: effect on prolongation of survival and improvement of quality of life, Hepato-gastroenterology, 46, 28, 2662-2668, 1999. ↩