The tree fungus known as reishi has a long history of use in China and Japan as a semi-magical healing herb. More revered than ginseng and, up until recently, more rare, many stories tell of people with severe illnesses journeying immense distances to find it. Presently, reishi is artificially cultivated and widely available in stores that sell herb products.
Reishi (like its fungi “cousins” maitake , Coriolus versicolor , and shiitake ) is marketed as a kind of cure-all, said to strengthen immunity , help prevent cancer , and also possibly treat cancer as well. It is also said to be useful for autoimmune diseases (such as myasthenia gravis and multiple sclerosis ), viral infections, high blood pressure , diabetes , enhancing mental function , altitude sickness , ulcers , and insomnia . However, while there has been a great deal of basic scientific research into the chemical constituents of reishi, reliable double-blind, placebo-controlled studies are all but nonexistent. (For information on why such studies are essential, see Why Does This Database Rely on Double-blind Studies? )
For example test tube studies indicate that reishi has immunomodulatory effects. 1-5 This means that reishi may affect the immune system, but not necessarily that it strengthens it. (Alternative medicine proponents often blur the difference between these two ideas.) However, one, small, double-blind, placebo-controlled human trial failed to find any significant immunomodulatory effects. 23 Other weak evidence hints that reishi may have chemopreventive properties, suggesting that it may help prevent cancer. 4,6-12 However, a great many substances fight cancer in the test tube, while few actually help people with the disease.
Other highly preliminary forms of evidence suggest that reishi may have antiviral effects 13-19 and possibly antibacterial effects as well. 20 However, it is a long way from studies of this type to meaningful clinical uses.
Contemporary herbalists regard reishi as an adaptogen, a substance believed to be capable of helping the body resist stress of all kinds. (For more information on adaptogens, see the article on Ginseng .) However, there is no meaningful evidence to support this claim.
One questionable double-blind study performed in China reportedly found reishi helpful for neurasthenia. The term neurasthenia is seldom used in modern medicine; it generally indicates fatigue due to psychological causes. 22
The usual dosage of reishi is 2 g to 6 g per day of raw fungus, or an equivalent dosage of concentrated extract, taken with meals. In traditional Chinese medicine, reishi is often combined with related fungi, such as shiitake, hoelen, or polyporus. It is often taken continually for its presumed overall health benefits.
Because it is used as food in Asia, reishi is generally regarded as safe. One small study evaluating the safety of reishi when taken at a dose of 2 g daily for 10 days failed to find any evidence of ill effects. 23 However, another study found indications that reishi impairs blood clotting. 21 For this reason, prudence suggests that individuals with bleeding problems should avoid reishi; the herb should also be avoided in the period just before and after surgery or labor and delivery. Furthermore, individuals taking medications that impair blood clotting, such as aspirin, warfarin (Coumadin), heparin, clopidogrel (Plavix ), pentoxifylline (Trental ), or ticlopidine (Ticlid), should only use reishi under a doctor’s supervision.
Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established.
4. Wang YY, Khoo KH, Chen ST, et al. Studies on the immuno-modulating and antitumor activities of Ganoderma lucidum (Reishi) polysaccharides: functional and proteomic analyses of a fucose-containing glycoprotein fraction responsible for the activities. Bioorg Med Chem. 2002;10:1057-1062.
6. Bao XF, Zhen Y, Ruan L, Fang JN. Purification, characterization, and modification of T lymphocyte-stimulating polysaccharide from spores of Ganoderma lucidum. . Chem Pharm Bull (Tokyo). 2002;50:623-629.
8. Lu H, Kyo E, Uesaka T, Katoh O, Watanabe H. Prevention of development of N,N'-dimethylhydrazine-induced colon tumors by a water-soluble extract from cultured medium of Ganoderma lucidum (Rei-shi) mycelia in male ICR mice. Int J Mol Med. 2002;9:113-117.
9. Lu H, Uesaka T, Katoh O, Kyo E, Watanabe H. Prevention of the development of preneoplastic lesions, aberrant crypt foci, by a water-soluble extract from cultured medium of Ganoderma lucidum (Rei-shi) mycelia in male F344 rats. Oncol Rep. 2001;8:1341-1345.
14. Eo SK, Kim YS, Lee CK, Han SS. Possible mode of antiviral activity of acidic protein bound polysaccharide isolated from Ganoderma lucidum on herpes simplex viruses. J Ethnopharmacol. 2000;72:475-481.
17. Kim YS, Eo SK, Oh KW, Lee C, Han SS. Antiherpetic activities of acidic protein-bound polysacchride isolated from Ganoderma lucidum alone and in combinations with interferons. J Ethnopharmacol. 2000;72:451-458.
18. Min BS, Nakamura N, Miyashiro H, Bae KW, Hattori M. Triterpenes from the spores of Ganoderma lucidum and their inhibitory activity against HIV-1 protease. Chem Pharm Bull (Tokyo). 1998;46:1607-1612.
19. Oh KW, Lee CK, Kim YS, Eo SK, Han SS. Antiherpetic activities of acidic protein-bound polysacchride isolated from Ganoderma lucidum alone and in combinations with acyclovir and vidarabine. J Ethnopharmacol. 2000;72:221-227.
Last reviewed December 2015 by EBSCO CAM Review Board
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