1. Boost the Immune System
One of the most important effects of the reishi mushroom is that it can boost your immune system (4).
While some details are still uncertain, test-tube studies have shown that reishi can affect the genes in white blood cells, which are critical parts of your immune system.
What’s more, these studies have found that some forms of reishi may alter inflammation pathways in white blood cells (5).
Research in cancer patients has shown that some of the molecules found in the mushroom can increase the activity of a type of white blood cell called natural killer cells (6).
Natural killer cells fight infections and cancer in the body (7).
Another study found that reishi can increase the number of other white blood cells (lymphocytes) in those with colorectal cancer (2).
Although most immune system benefits of reishi mushroom have been seen in those who are ill, some evidence has shown that it can help healthy people, too.
In one study, the fungus improved lymphocyte function, which helps fight infections and cancer, in athletes exposed to stressful conditions (8, 9).
However, other research in healthy adults showed no improvement in immune function or inflammation after 4 weeks of taking reishi extract (10).
Overall, it is clear that reishi impacts white blood cells and immune function. More research is needed to determine the extent of the benefits in the healthy and ill.
2. Anti-Cancer Properties
Many people consume this fungus due to its potential cancer-fighting properties (11, 12).
In fact, one study of over 4,000 breast cancer survivors found that around 59% consumed reishi mushroom (13).
Additionally, several test-tube studies have shown that it can lead to the death of cancer cells (14, 15, 16).
Yet the results of these studies do not necessarily equate to effectiveness in animals or humans.
Some research has investigated if reishi could be beneficial for prostate cancer due to its effects on the hormone testosterone (17, 18).
While one case study showed that molecules found in this mushroom may reverse prostate cancer in humans, a larger follow-up study did not support these findings (19, 20).
Reishi mushroom has also been studied for its role in preventing or fighting colorectal cancer (2, 21).
Some research showed that one year of treatment with reishi decreased the number and size of tumors in the large intestine (21).
What’s more, a detailed report of multiple studies indicated that the mushroom can beneficially affect cancer patients (22).
These benefits included increasing the activity of the body’s white blood cells, which help fight cancer, and improving quality of life in cancer patients.
However, researchers state that reishi should be administered in combination with traditional treatment rather than replacing it (22).
What’s more, many of the studies of reishi mushroom and cancer were not high-quality. Because of this, much more research is needed (11, 23).
3. Fight Fatigue and Depression
Reishi’s effects on the immune system are often most emphasized, but it has other potential advantages as well.
These include reduced fatigue and depression, as well as improved quality of life.
One study examined its effects in 132 people with neurasthenia, a poorly defined condition associated with aches, pains, dizziness, headaches and irritability (24).
The researchers found that fatigue was reduced and well-being was improved after 8 weeks of taking the supplements.
Another study found that fatigue was reduced and quality of life was improved after 4 weeks of taking reishi powder in a group of 48 breast cancer survivors (25).
What’s more, the people in the study also experienced less anxiety and depression.
While reishi mushroom may hold promise for people with certain diseases or illnesses, it is not clear if it would benefit those who are otherwise healthy.
4. Heart Health
One 12-week study of 26 people showed that reishi mushroom may increase “good” HDL cholesterol and decrease triglycerides (26).
However, other research in healthy adults showed no improvement in these heart disease risk factors (10).
Moreover, a large analysis demonstrated no beneficial effects for heart health after examining five different studies containing around 400 people. The researchers found that consuming reishi mushroom for up to 16 weeks did not improve cholesterol (27).
Overall, more research is needed in regard to reishi mushrooms and heart health.
5. Blood Sugar Control
Several studies have indicated that molecules found in the reishi mushroom can decrease blood sugar in animals (28, 29).
Some preliminary research in humans reported similar findings (30).
However, the majority of research has not supported this benefit. After evaluating hundreds of participants, researchers found no benefits for fasting blood sugar (27).
Mixed results were seen for blood sugar after meals. In some cases, reishi mushroom lowered blood sugar, but in other cases, it was worse than a placebo.
Again, more research is needed here as well.