Reishi mushroom can cause dizziness, dry mouth, itching, nausea, stomach upset, and rash. Taking Reishi mushroom may be riskier if you have low blood pressure or if you are taking treatment to raise it, if you are taking medications for diabetes, or if you have immune system disorders or are taking medications. Liver toxicity is a dangerous side effect that can result in death. Side effects of reishi mushroom may include nausea and insomnia in some people with cancer.
Rarely, liver toxicity has been reported as a side effect. The Komen Foundation notes that reishi mushroom extract is possibly safe for up to 1 year when a person takes it orally. Despite the popularity of reishi mushrooms in Eastern medicine, there are few human studies on the effects of this mushroom. Many health-promoting claims about reishi mushrooms stem from anecdotal evidence or cultural uses, rather than rigorous scientific research or exhaustive studies (Wachtel-Galor, 201. Reishi mushrooms are often dried, ground and powdered, and can be found in coffees, teas, powders, or tablets).
However, they also point out that taking powdered reishi mushrooms for more than 1 month can be toxic to the liver. While the reishi mushroom has cultural significance, it's important to note that research on how this mushroom specifically affects human health is evolving, but is still limited. This advice also applies to those taking immunosuppressants, as reishi mushroom supplements may counteract their effectiveness. Reishi mushrooms may not be the most effective route to promote strong levels of antioxidants in the body.
A number of factors can influence the possible side effects of mushrooms, such as the dosage, the shape of the mushroom (natural, powder, or extract), and how long you take the mushrooms. Adding alternative treatments, such as reishi mushrooms, to the mix should always be an informed decision between you and your healthcare provider, and is never recommended as a standalone treatment. Therefore, people whose doctors have scheduled surgery and people with bleeding disorders should not take reishi mushrooms. A review of five randomized controlled trials that investigated the use of reishi mushrooms in the treatment of cancer revealed that those who received extracts as part of chemotherapy or radiation therapy had more active immune cells, a greater likelihood of an anti-tumor response and a better quality of life, although these benefits were mild and larger studies are needed (Jin, 201).
Reishi mushrooms are highly valued in traditional medicine offices across Asia for their role in health (Ganeshpurkar, 20). Many people believe that reishi mushrooms provide some health benefits, mainly improving the immune system and treating cancer. People who already have low blood pressure or who are taking blood pressure medications may want to avoid reishi mushrooms.