Fungi (yeasts, moulds, mushrooms) have played an important role in Chinese culture for at least 4000 years, with oral tradition dating back perhaps 7000 years. Written and oral accounts refer to the healing powers of several varieties of medicinal fungi, the spores of the common puffball were probably the most widely used initially, applied externally to heal scalds, burns, and general pains of the body, while the giant Agarikon fungi was widely chosen as a curative for stomach ailments.
Fungi and its various medicinal applications began being listed in Chinese medicinals, particularly the Shen nung Pen ts’ao king, and the Ming I pie lu, about 3000 years ago, and were even mentioned in classic Chinese literature. One family of fungi referred as a chi (quite possibly the reishi), has several entries in both volumes, including the green variety which is said to “brighten the eye, strengthen the liver, quiet the spirits, improves the memory, and prolongs life”, while the yellow variety is said to “act on the spleen as a tonic and constructive”.
Similarly, a number of other varieties of fungi are listed for their purported healing properties. Among those, three varieties in particular, Hoelen (a mushroom cultivated on the roots of the Chinese red pine trees), caterpillar fungus, and ergot are currently drawing broad interest from the Western medical community. Interest that has led to the discovery of exactly why these plants are beneficial to human health.
One of the greatest findings in recent years concerning the natural curative powers of plants is scientific proof that fungi contain a number of compounds that can stimulate immune function and inhibit tumour growth in humans.
Among these compounds, those termed polysaccharides, which are large, complex chains of molecules constructed of smaller units of sugar molecules, are also found in lichens (a symbiosis of fungus and green alga), bacteria, and even from the cell walls of yeast (a carbohydrate called zymosan). These immune-activating polysaccharides are similar to those found in more complex plants such as Echinacea and astragalas (a widely used Chinese herb) – these have been found to do amazing things to our body.
These giant polysaccharide molecules are similar to ones found in the cellular membranes of bacteria, and thus, trick our immune system into believing it is being invaded, and accordingly, it mounts an immune response. While this perceived threat poses no actual danger to our bodies, this immune response triggers the increase of a number of powerful immune activities including macrophage and “killer” T-cell (white blood cell) activity. Polysaccharides are not the only active components found in fungi, nor is immune and anti-tumour activity the only influence they have.
Smaller compounds such as terpenes and steroids present have also been shown to resist the growth of tumours, and a number of what are called “protein-bound” polysaccharides have even shown to have antibiotic and anti-viral properties, as well as the ability to lower blood pressure and reduce blood-level lipids (fats) and sugar. These properties make fungi especially useful in treating infections, flu, diabetes, various heart conditions, and according to many studies, perhaps the HIV. But as research into these fascinating plants continues, there’s no doubt but that other benefits will be discovered.
I will be looking at the background and medicinal uses of the Shiitake mushroom.
Lentinula edodes, common Japanese name, Shiitake, is an edible mushroom, which is now 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.
Published evidence finds that the anti-tumour claims are substantiated, especially those of the lentinan polysaccharide isolated from Shiitake - the most highly researched bioactive molecule isolated from shiitake is the pure b(1à3)-D-glucan lentinan. Lentinan is also found to be an immunomodulator, although the medicinal value of these findings are yet to be reliably established. Cholesteremic effects were shown but there was disagreement over the details of the effects. It was concluded that Lentinula edodes does have much potential in medicine but further research is needed.
As an anti-cancer drug, it has proven effective in prolonging the survival of cancer patients, particularly those with gastric and colorectal cancer. Work in both human and murine models has shown both Shiitake and lentinan extract to be effective anti-tumour agents, and extensive work in Japan has lead to them pioneering the use of lentinan in clinical medicine. The results are very promising but until more clinical studies are conducted particularly with randomised controlled trials, it seems unlikely that lentinan will be accepted into Western clinical medicine.
Active hexose correlated compound (AHCC) is an α-glucan-rich compound isolated from Shiitake. In Japan, AHCC is the second most popular complementary and alternative medicine used by cancer patients. In addition, animal research has shown that AHCC may increase the body’s resistance to pathogens as shown in experiments with the influenza virus, West Nile encephalitis virus, and bacterial infection. Animal research has shown AHCC may enhance immune function.
Oral indigestion of whole mushroom extracts has shown to modulate certain immune functions, although the oral administration of the polysaccharide lentinan is ineffective. The differences in effectiveness between Shiitake and the lentinan extracted indicates that other constituents of the mushroom may have a bioactive role – the mechanisms are yet unclear.
Other significant effects of Shiitake’s immunomodulatory effects are increased host resistance to bacterial and viral infections. Lenthionine, a sulphur containing peptide from Shiitake has anti-bacterial and anti-funal activity and bis[(methylsulfonyl)methyl]disulphide, 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 Shiitake’s antibacterial components, and these have concentrated on their potential in terms of oral origin – there is a lack of significant studies in this area.
The human immunodeficiency virus (HIV) has shown some weakness to Shiitake extracts in several experiments. Some studies have shown 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 – although there has not been much further progress with these findings. Most reported results have been conducted in vitro and as yet no studies on human participants have been established. Therefore the possibility of Shiitake extracts being used in HIV treatment is not yet in reach.
Cardiovascular (CV) disease is the biggest cause of mortality worldwide and high blood cholesterol levels are on important risk factor in development of CV problems, so any hypocholesteremic effects are of great importance.
Shiitake’s ability to lower cholesterol was first reported in the 1960’s. It was found that a diet supplemented with the dried ground sporophores lowered average plasma cholesterol when fed to rats. In spontaneously hypertensive rats dried Shiitake decreased both the VLDL (very low density lipoprotein) and HDL (high density lipoprotein) cholesterol levels and therefore prevented blood pressure increase in hypertension, and in human testing, serum cholesterol was decreased in groups of women fed fresh, dried of UV-irradiated Shiitake.
Recently studies have noted that Shiitake mushrooms contain high amounts of vitamin D after brief exposure to sunlight or UV light.
The whole fruiting body of the Shiitake mushroom is used, and the best remedy is to ingest the entire mushroom. However, caution should be taken, as consumption of raw or slightly cooked Shiitake mushrooms can cause “an erythematous, micro-papular, streaky, extremely pruriginous rash” that occurs all over the body including face and scalp, which appears about 48 hours after consumption and disappears after 10 days. Thorough cooking eliminates the effect.