Lingzhi
Lingzhi (traditional Chinese: ; simplified Chinese: ; Japanese: reishi; Korean: yeongji, hangul: ) is the name for one form of the mushroom Ganoderma lucidum, and its close relative Ganoderma tsugae, which grows in the northern Eastern Hemlock forests. These two species of bracket fungus have a worldwide distribution in both tropical and temperate geographical regions, including North and South America, Africa, Europe, and Asia, growing as a parasite or saprotroph on a wide variety of trees.  Ganoderma lucidum enjoys special veneration in Asia, where it has been used in traditional Chinese medicine as a herbal medicine for more than 4,000 years, making it one of the oldest mushrooms known to have been used in medicine. Similar species of Ganoderma have been found growing in the Amazon, according to mycologist Christopher Hobbs. 
The word lingzhi, in Chinese, means "herb of spiritual potency" and has also been described as "mushroom of immortality". Because of its presumed health benefits and apparent absence of side-effects, it has attained a reputation in the East as the ultimate herbal substance. Lingzhi has now been added to the American Herbal Pharmacopoeia and Therapeutic Compendium.

# Taxonomy and naming
The name Ganoderma is derived from the Greek ganos/ "brightness, sheen", hence "shining" and derma/ "skin", while the specific epithet lucidum in Latin for "shining" and tsugae refers to being of the Hemlock (Tsuga). Another Japanese name is mannentake, meaning "10 000 year mushroom".
There are multiple species of lingzhi, scientifically known to be within the Ganoderma lucidum species complex and mycologists are still researching the differences between species within this complex of species.

# Description
Lingzhi is a polypore mushroom that is soft (when fresh), corky, and flat, with a conspicuous red-varnished, kidney-shaped cap and, depending on specimen age, white to dull brown pores underneath. It lacks gills on its underside and releases its spores through fine pores, leading to its morphological classification as a polypore.

## Varieties
Ganoderma lucidum generally occurs in two growth forms, one, found in North America, is sessile and rather large with only a small or no stalk, while the other is smaller and has a long, narrow stalk, and is found mainly in the tropics. However, many growth forms exist that are intermediate to the two types, or even exhibit very unusual morphologies, raising the possibility that they are separate species. Environmental conditions also play a substantial role in the different morphological characteristics lingzhi can exhibit. For example, elevated carbon dioxide levels result in stem elongation in lingzhi. Other forms show "antlers', without a cap and these may be affected by carbon dioxide levels as well.
According to The Chinese Herbal Materia Medica (), lingzhi may be classified into six categories according to their shapes and colors, each of which is believed to nourish a different part of the body.
- Red - heart
- Purple - joints
- Green - liver
- White - lungs and skin
- Yellow - spleen
- Black - kidneys and brain

# Biochemistry
Ganoderma lucidum is the only known source of a group of triterpenes, known as ganoderic acids, which have a molecular structure similar to steroid hormones. It is a source of biologically active polysaccharides with presumed medicinal properties, and it also contains:
- ergosterol
- coumarin
- mannitol
- lactones
- alkaloids
- unsaturated fatty acids
- vitamins and minerals.
Unlike many other mushrooms, which have up to 90% water content, fresh Lingzhi only contains about 75% water.

# Habitat
In nature, Lingzhi grows at the base and stumps of deciduous trees, especially maple (National Audubon Society; Field guide to Mushrooms,1993). Only two or three out of 10,000 such aged trees will have Lingzhi growth, and therefore its wild form is generally rare. Today, Lingzhi is effectively cultivated both indoors under sterile conditions and outdoors on either logs or woodchip beds.

# History
The Shen Nong's Herbal Classic, a 2000-year old medicinal Chinese book considered today as the oldest book on oriental herbal medicine, classifies 365 species of roots, grass, woods, furs, animals and stones into three categories of herbal medicine:
- The first category, called "superior", includes herbs effective for multiple diseases and are mostly responsible for maintaining and restoring the body balance. They have almost no unfavorable side-effects.
- The second category comprises tonics and boosters, for which their consumption must not be prolonged.
- The third category must be taken, usually in small doses, and for the treatment of specific ailments only.
Lingzhi ranked number one of the superior medicines, and was therefore the most exalted medicine in ancient times.

# Current usage
Lingzhi can be found for sale in many Asian markets as well as Western health shops. Extracts of 'lingzhi,' which may also be called 'reishi' are also available. In general, a hot water extract is best at concentrating the polysaccharides in lingzhi and alcohol extracts are best at concentrating the triterpenoids in lingzhi but an extract can also be made with a blend of both extracts.

## Medicinal uses
Lingzhi may possess some anti-tumor, immunomodulatory and immunotherapeutic activities, supported by some studies on polysaccharides, terpenes, and other bioactive compounds isolated from fruiting bodies and mycelia of this fungus (reviewed by R. R. Paterson). However, the efficacy of these compounds in the treatment of cancer has not yet been shown in clinical trials. Moreover, as with any herb, variation between preparations and potential negative side effects cannot be ruled out. It is understood as adaptogenic, anti-allergenic and anti-hypertensive due to the presence of triterpenes. Apart from these properties, lingzhi has been found to be anti-inflammatory, antiviral, anti-parasitic, anti-fungal, antidiabetic, anti-hypotensive, and protective of the liver. It has also been found to inhibit platelet aggregation, and to lower blood pressure, cholesterol and blood sugar. 
Because of these properties, lingzhi has been regarded as blood pressure stabilizer, antioxidant, analgesic, a kidney and nerve tonic. It has been used in bronchitis prevention and in cardiovascular treatment, and in the treatment of high triglycerides, high blood pressure, hepatitis, allergies, chemotherapy support, HIV support, and even for fatigue and altitude sickness. 
Some peer-reviewed studies indicate that ganoderic acid has some protective effects against liver injury by viruses and other toxic agents in mice, suggesting a potential benefit of this compound in the treatment of liver diseases in humans.
Although the experiences in fighting cancer are more inconsistent, the extract has been claimed to be effective in regressing tumors. The results depend on the type of cancer and the severity of the condition. It is usually recommended that it be used in combination with other prescribed medical treatments and as part of a fu zheng formula with a variety of supporting herbs. The Ganoderma extract has been employed to help substantially reduce or eliminate the side-effects of radio- and chemotherapies if it is taken before, during and after the treatments. It has been found clinically to reduce side-effects like hair loss, nausea, vomiting, stomatitis, sore throat, loss of appetite and insomnia.

## Preparation
Because mushrooms contain chitin which locks up medicinal components, preparations of lingzhi are unlikely to be medicinally active unless there has been a prolonged water extraction. Simply tincturing the mushroom in ethanol or powdering it and encapsulating it makes preparations that are essentially inert and may account for some of the inconsistency in research results.  Additionally, mushrooms traditionally incorporate or transform constituents from their host trees and mycelial fractions grown in sawdust or other substrate may differ appreciably from the whole fungus.
Lingzhi is traditionally prepared by simmering in water. Thinly sliced or pulverized lingzhi (either fresh or dried) is added to a pot of boiling water, the water is then brought to a simmer, and the pot is covered; the lingzhi is then simmered for two hours.  The resulting liquid should be fairly bitter in taste, with the more active red lingzhi more bitter than the black. The process may be repeated.  Alternatively, it can be used as an ingredient in a formula decoction or used to make an extract (in liquid, capsule, or powder form). The more active red forms of lingzhi are far too bitter to be consumed in a soup, as long cooked shitake mushrooms might be.

## Side effects
It has been shown in some studies that long term use of Lingzhi (usually four months or so) can result in some mild side effects, including dryness of the nasal passages, mouth and throat, as well as stomach upset and nosebleed. However, these effects were avoided by discontinuing use of the mushroom for one month after taking it for four months, and taking it again for four months and so on.

# Modern scientific studies
Numerous studies of lingzhi, mainly in China, Korea, Japan and the United States, have shown its effectiveness in the treatment of a very wide range of diseases and symptoms.  But the studies have not given any explanation of exactly how lingzhi has so many diverse effects, because none of the known active components taken alone have produced results as powerful as the intake of lingzhi itself, suggesting synergy is important.  For example, reports of lingzhi's effect on stamina, appetite, and other human conditions are largely anecdotal and haven't been studied scientifically.  It is perhaps more comprehensible at this time to explain lingzhi's "miraculous powers" from the traditional Chinese medicine point of view.
In the West, scientists have traditionally separated and classified each disease meticulously, and have specialized in each of them to such a degree that it seems as if each disease is autonomous and standing alone. Oriental medicine, resulting from knowledge accumulated through 4,000 years of human observation, asserts that health can be maintained by sustaining the proper balance within the body and that diseases can be cured by restoring this balance through nutrition, including medicinal herbs, exercise and mental peace. Traditional oriental medicine believes that a disease is but the mere tip of an iceberg, the result of the underlying imbalance of the body which must be restored.
Observations have shown that lingzhi generally has only slight side effects and can be consumed in high doses, in parallel with other medications. Its main properties are adaptogenic which mean that it is nontoxic, it works in a generalized manner on the hypothalamic-pituitary-adrenal axis and the neuroendocrine system.  Its actions are alterative, enhance the immune system and lessen nervous tension.  These properties are conducive to normalizing and balancing the body (homeostasis and allostasis), and as a result, lingzhi is able to help the body cure a multitude of disease states from within.
Lingzhi has been found to strengthen the respiratory system and to have a healing effect on the lungs, and is particularly beneficial for individuals with asthma, cough and other respiratory complaints. At least one population study conducted in the 1970s confirms this claim. When more than 2,000 Chinese with chronic bronchitis took lingzhi syrup, 60 to 90% felt better within two weeks and reported an improved appetite, according to an article entitled, Medicinal Mushrooms, written by Christopher Hobbs, and published in Herbs for Health, Jan/February 97.
In Japan, after daily injections in mice with cancer it was reported that tumors in 50% of the animals had completely regressed within 10 days. (Ikekawa et al,1968;Japanese Journal of Cancer Research; 59: 155-157) The host-dependent anti-tumor activity has been subsequently confirmed to be from the polysaccharide fractions of Ganoderma by Sasaki et al.. Multiple similar studies subsequently confirms this observation and anti-tumor efficacy of Ganoderma has been demonstrated from various species, at different stages of growth and using different solvents for extraction and different routes of administration. Anti-tumor activity has been demonstrated in vitro as well as in syngeneic tumor systems in animals. However, no human trials of Ganoderma against cancer in peer reviewed journals nor any controlled clinical trials in humans have yet been conducted or published.
There has been research showing lingzhi an effective supplement during chemotherapy or radiotherapy to reduce side-effects such as fatigue, loss of appetite, hair loss, bone marrow suppression and risk of infection. Ganodermas was shown effective against fatigue , hair loss , and bone marrow suppression .  There is similar clinical evidence for other glucan BRMs applied in the setting of cancer chemotherapy or radiotherapy  lending further support to the supplementation of Ganoderma in combination with cytotoxic cancer therapies. The recommended dose should be in the range of five to ten grams of fruiting body or equivalent per day .
In an animal model, Ganoderma has been demonstrated to effectively prevent cancer metastasis , and these results are comparable to those of Lentinan from shitake mushrooms   While only anecdotal or clinical data exists indicating ganoderma supplementation may enhance survival of human cancer patients, this survival advantage has been demonstrated for a number of comparable glucan BRMs like lentinan. Lentinan use in advanced gastric cancer demonstrated a significant life span prolongation advantage at 1, 2, 3 and 4 years in a randomized control trial .  Lentinan is however injected. More appropriate for comparison to Ganoderma is perhaps PSK or PSP, which are orally administered. Mitomi et al.  found significantly improved survival and disease-free survival (P=0.013) in colorectal cancer given PSK supplementation over three years when compared to control in a multi-center randomized controlled trials.