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.


What Is Reishi Used for Today?

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.

Safety Issues

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.


Interactions You Should Know About

If you are taking blood-thinning medications, such as aspirin]]> , warfarin ( ]]>Coumadin]]> ), ]]>heparin]]> , clopidogrel ( ]]>Plavix]]> ), ]]>pentoxifylline]]> (Trental), or ]]>ticlopidine]]> (Ticlid), use reishi only under a doctor's supervision.