Reishi mushroom: benefits, dosage, side effects

Have you tried mushroom coffee yet? While it may sound unusual, instead of adding sugar or cream to your coffee, you can now brew blends of coffee and mushroom extracts, with Reishi mushrooms being one of the more common varieties on the market.

Thought to promote health by boosting the immune system, reishi mushrooms have been used in traditional Chinese medicine and throughout Asia for thousands of years. They are now gaining ground in new foods and beverages (who would have thought people would be sipping on mushrooms for breakfast?), as well as dietary supplements across the globe (Wachtel-Galor, 2011). 

While the reishi mushroom holds cultural significance, it’s important to note that research on how this fungus specifically impacts human health is evolving but still limited. So, before you rush to the store to stock up on the latest products with promising claims of immunity and vitality, here’s what you need to know about reishi mushrooms. 

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Reishi mushrooms grow on plum trees throughout Asia (Jin, 2016). They are scientifically known as both Ganoderma lucidum and Ganoderma lingzhi and are generally categorized under the umbrella of medicinal mushrooms. Lingzhi is the common name for the mushroom in China, whereas reishi is the common name in Japan. While fresh reishi mushrooms are technically edible, their coarse, woody texture and bitter taste don’t make them too enticing (Wachtel-Galor, 2011). Supplementation of the mushroom from powders or extracts of specific molecules (like beta-glucans or triterpenoids) is more common. 

In Asia, the mushroom has been used for thousands of years to increase energy, boost immune function, and promote a long healthy life—which is why they sport the nickname, the mushroom of immortality (Jin, 2016). 

Some research attributes these medicinal properties to two components of the mushroom: beta-glucans—a type of fiber found in the cell wall of some bacteria and fungi that may support the immune system—and triterpenoids—plant compounds (phytonutrients) that may have anti-inflammatory and pain-relieving qualities (Jin, 2016; Camilli, 2018; Ganeshpurkar, 2010; Bishayee, 2011). 

Many health-promoting claims of reishi mushrooms stem from anecdotal evidence or cultural uses rather than rigorous scientific research or large studies (Wachtel-Galor, 2011). 

Most research on reishi has been conducted in Petri dishes (in vitro) or in mice and rats in labs—reporting positive findings and using strong language like anti-cancer, anti-tumor, and immunomodulatory to describe the benefits (Klupp, 2015). However, this is often a bit of a stretch, especially since studies on reishi use in people are limited, and the available studies aren't always of the highest quality (Klupp, 2015). 

Here’s where the research of reishi mushrooms for human health currently stands. 

Reishi mushrooms’ effects on the immune system

Immune health is likely the most widespread claim of the reishi mushroom. There are lab and animal studies showing how reishi mushrooms and their extracts can impact the number and activity of specific immune cells (Jin, 2016). But in people, supplementation has mainly been investigated in the context of immune health in people with cancer.

A review of five randomized-controlled trials investigating the use of reishi mushrooms in cancer treatment found that those who received extracts as part of their chemotherapy or radiation treatment had more active immune cells, a higher likelihood of an antitumor response, and an improved quality of life—although these benefits were slight and bigger studies are needed (Jin, 2016). 

Adding alternative treatments like reishi mushrooms to the mix should always be an informed decision between you and your healthcare provider, and it’s never recommended as a standalone treatment. 

Reishi mushroom for blood sugar, blood pressure, and cholesterol

Human studies don’t currently support the use of reishi mushrooms in promoting healthy blood sugar levels or in lowering blood pressure, cholesterol, or triglyceride levels (Klupp, 2015).

A review of five studies, including data on 398 people with type II diabetes, found that reishi mushroom supplementation didn’t improve cardiovascular risk factors in those people (Klupp, 2015). Another study including 84 people with type II diabetes found that supplementing with reishi mushroom (alone or combined with another mushroom extract) had no impact on blood sugar levels or triglycerides compared to those not supplementing (Klupp, 2016). 

Reishi mushroom and its role as an antioxidant

Antioxidants, which are found in foods like fruits, vegetables, and mushrooms, play a role in combating oxidative stress and damage from free radicals in the body that can contribute to chronic conditions like cancer, heart disease, and type II diabetes (Sharifi-Rad, 2020). 

Lab and animal studies indicate that reishi mushrooms act as an antioxidant in the body, but an older four-week randomized controlled trial of 18 healthy adults found that reishi mushrooms had no effect on actual measures of antioxidant levels (Cör, 2018; Wachtel-Galor, 2004). 

Reishi mushrooms may not be the most effective route to promote strong levels of antioxidants in the body. Instead, focus on eating a diet rich in plant-based antioxidants like tomatoes (that contain lycopene) or spinach (that contains beta-carotene).  

Reishi mushrooms are often dried, ground, and powdered and can be found in coffees, teas, powders, or tablets. But, different parts of the mushroom may be used in different supplements. 

The whole mushroom, the fruiting body (the visible part of the mushroom that is eaten), the mycelium (the root-like system), or certain isolated extracts that are isolated can all be used (Wachtel-Galor, 2011). And the supplement may not specify what part of the mushroom it uses. 

There is currently no consensus on the most “effective” amount of reishi mushroom. Studies have looked at supplemental doses ranging from 1.5 g to 9 g of dried extracts per day (Klupp, 2015). And 1 g of the dried extract is about the same as 9 g of fresh reishi mushroom. 

It can be difficult to determine how much reishi mushroom is in some products because it’s frequently added as part of a proprietary blend of “medicinal” mushrooms. The quantity listed on the label is for the blend—not reishi mushroom specifically. 

Studies show that there may be minor side effects like nausea to reishi mushroom supplementation. Rare cases of liver damage have been reported after consuming reishi mushroom powder, but generally, reishi mushroom does not build up to dangerous levels in the body (Jin, 2016; Klupp, 2015; Wanmuang, 2007). 

Extracts of reishi mushrooms may have blood-thinning capabilities, so high doses of reishi mushroom supplementation may increase the chance of bleeding in people with bleeding disorders and may interact with blood-thinning medications (Poniedziałek, 2019). 

Reishi mushrooms have also not been studied in pregnant or breastfeeding women, so it’s advised you talk to your healthcare provider before using this supplement (Klupp, 2015; Klupp, 2016). 

Reishi mushrooms are highly regarded in traditional medicine practices throughout Asia for their role in health (Ganeshpurkar, 2010). 

Today, reishi is mostly promoted for its potential immune benefits. And while lab and animal studies show some promising effects, there need to be more studies in human beings to really support reishi mushrooms for those purposes. 

If the benefits of reishi mushrooms are of interest to you, it’s best to talk with a healthcare professional before adding a reishi mushroom supplement—or any supplement—to your routine.

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Current version

November 23, 2021

Written by

Molly Knudsen, MS, RDN

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.