Health Benefits of Reishi

Can the Chinese mushroom boost immunity and fight infection?

Reishi mushrooms
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Reishi is a type of mushroom used to promote health and longevity in traditional Chinese medicine and Ayurvedic medicine. Also known as the lingzhi mushroom, reishi had a red, kidney-shaped cap and finger-like spores on its underside rather than gills. The species of reishi most commonly used for medicine is Ganoderma lucidum.

Many of the purported benefits of reishi are attributed to a group of compounds called ganoderic acids, which have a similar structure to steroid hormones. Reishi is also rich in beta-glucans (which can help improve cholesterol and glucose levels) and mannitol (which can aid in eye function).

Because of its bitter taste and woody texture, reishi is not typically used for cooking. However, it is can be used to make tea or medicinal tonics.

The term "lingzhi" was derived from the Chinese words ling (meaning spirit) and zhi (meaning plant). The Japanese "reishi" is more commonly used today, the term of which is loosely adapted from "lingzhi."

Health Benefits

Alternative practitioners believe that reishi is able to treat fatigue, high cholesterol, high blood pressure, and inflammation by bolstering the immune system. Others have it ascribed it with "cure-all" properties that are far-reaching in their scope.

Among some of the conditions reishi is reported to treat are:

  • Acne
  • Allergies
  • Arthritis
  • Cancer
  • Common cold
  • Herpes simplex
  • HIV
  • Hair loss
  • Lyme disease
  • Obesity
  • Oral thrush
  • Ulcerative colitis
  • Uterine fibroids
  • Vitiligo
  • Yeast infections

Few of these health claims are supported by research. Of the studies currently available. most are limited to test tubes or small-scale animal or human trials.

Much of the current scientific focus has been placed on reishi's effect on viral and bacterial infections, diabetes, and cancer. While some of the results are promising, none are robust enough to recommend reishi as a treatment for any medical condition.

Viral Infections

A number of lab studies have shown that extracts of G. lucidum have been able to neutralize herpes simplex virus 1 (HSV-1), herpes simplex virus 2 (HSV-2), herpes zoster virus (HSV) in the test tube. Similarly, the ganoderic acids derived from reishi appeared able to control of HIV and hepatitis B viral activity to a certain degree.

While promising, the same level of control has not been seen outside of the test tube.

A 2007 study from Japan, involving 18 people, reported that a herbal remedy containing G. lucidum was able to shorten the duration of HSV-2 (genital herpes) outbreak from an average of 10.9 days to 4.0 days.

An earlier study from the same team reported that a G. lucidum extract was able to dramatically reduced postherpetic pain in two people with an HZV (shingles) infection and two people with treatment-resistant HSV-2.

The conclusions from both of the studies are limited by their size and the lack of qualitative measures for postherpetic pain.

Bacterial Infections

There is even less evidence supporting the antibacterial effects of reishi. Although there have several studies demonstrating how G. lucidum can neutralize bacteria like Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa in the test tube, there is little proof that consuming a reishi extract will do the same.

Of the available studies, an early investigation from Japan reported that a 2-milligram injection of G. lucidum extract in mice inoculated with E. coli improved survival rates from 33 percent to over 80 percent.

Other studies have found no effect, whether the extract was delivered orally or by injection.

Diabetes

The beta-glucans found in reishi are believed to aid in the management of diabetes. A number of animal studies have suggested that the oral administration of fungal beta-glucans reduced blood glucose levels by increasing the body's sensitivity to insulin.

Although some of the early studies had shown that G. lucidum exerted the same effect in mice, recent investigations have been mixed, with some showing benefits and others not.

One human study, involving 71 adults with type 2 diabetes, concluded that 1800-milligram extract of G. lucidum was able to significantly reduce blood glucose and HbA1C levels after 12 weeks compared to a placebo.

Further research would be needed to substantiate these findings.

Cancer

A number of lab studies have investigated reishi's ability to stimulate the immune response, most specifically with regards to the treatment of cancer. In the lab, reishi has been shown to kill tumor cells and boost the activity of immune cells such as natural killer cells (NK), T-cells, B-cells, tumor necrosis factor (TNF), and phagocytes (which ingest other cells). 

A 2016 review of studies from the University of Maryland evaluated five clinical trials involving the use of G. lucidum in treating cancer. The results of the studies were largely mixed and often contradictory.

Among some of the findings:

  • An increase in the immune response, as measured by T-cells, was relatively modest in people taking G. lucidum, ranging from 2 percent to 4 percent.
  • One of the reviewed studies reported an increase in NK cells; another showed no response.
  • A slightly larger number of people on chemotherapy reported a better quality of life when taking G. lucidum compared to those who didn't.
  • Few side effects were reported in any of the studies.

The investigators stated the quality of the studies ranged from low to very low. Based on the current body of research, they concluded that there was insufficient evidence to justify the use of G. lucidum in the treatment of cancer.

Possible Side Effects

Reishi is usually well-tolerated with few significant side effects. Some people may experience dry nose, dry throat, nausea, stomach upset, and allergy (usually to the mushroom's spores). Reishi also contains a substance known as coumarin that acts like a blood thinner, potentially triggering bloody stools, nosebleeds, and easy bruising.

There are also concerns about the long-term impact of reishi use. Reishi is metabolized mainly by the liver, and it is possible that long-term exposure (greater than a year) can lead to liver impairment and possibly damage.

To this end, reishi should be avoided in people with bleeding disorders or liver disease. It should not be used if you are taking anticoagulants like warfarin or are scheduled to have surgery as it may increase the risk of bleeding.

Reishi may also cause your blood pressure to drop and should be avoided if you are taking antihypertensive medications. Doing so may lead to hypotension (low blood pressure), triggering dizziness, fatigue, nausea, and blurry vision.

Due to the lack of safety research, reishi should be avoided in children, pregnant women, and breastfeeding mothers.

Dosage and Preparation

There are no guidelines directing the appropriate use of reishi. Most reishi supplements are available in capsule form and are considered safe in daily doses of between 500 to 1,000 milligrams. Reishi is also available in extracts, tinctures, tea, powders, and whole dried mushrooms.

Reishi products are readily found online and in health food stores and specialty supplements retailers. Always opt for products that are certified organic under the regulations of the U.S. Department of Agriculture (USDA). This can reduce your risk of exposure to pesticides and other toxins, particularly in imported herbal remedies.

Because herbal medicines do not have to undergo the rigorous testing and research that pharmaceutical drugs do, the quality can vary considerably. Some labeled "reishi" may not contain any G. lucidem at all or be mixed with a variety of inactive ingredients.

Unfortunately, few herbal manufacturers voluntarily submit the products for inspection by certifying bodies like the U.S. Pharmacopeia (USP). To ensure quality and safety, stay with recognized brands and don't be swayed by health claims that may or may not be true.

Other Questions

Are fresh reishi mushrooms available?

Fresh reishi mushrooms are harder to find in the United States than dried ones. A number of domestic growers have begun to cultivate them, mainly in the Pacific Northwest, but reliable suppliers are few and far between.

There are kits you can buy online that enable to grow your own reishi mushrooms. They are relatively easy to use and not all that costly. Be aware that the mushrooms grow very slowly and may take six months or more before you are ready to harvest any.

However, reishi growing does require a sterile environment and is prone to contamination if you don't use a still airbox to prevent airborne contaminants like mold. If growing reishi is too much of a hassle, the dried mushrooms are believed to be just as beneficial as fresh ones.

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