Should People With Breast Cancer Take Shiitake Mushroom Supplements?
Key Takeaways:
Although the evidence is in the very early stages, a few small studies suggest shiitake may boost the immune system and improve quality of life when taken during cancer treatment.
There’s no evidence that shiitake can treat cancer on its own, but it can be used as a complementary therapy.
Shiitake supplements are generally safe for most people, but they can cause gastrointestinal symptoms and some people are allergic to them.
Shiitake is a mushroom that people commonly cook and eat. For thousands of years, people have taken shiitake as a medicinal mushroom. Now, it’s becoming more popular, including among people with cancer, for its health benefits.
People often take shiitake supplements as an extract, powder, or capsule. You can also take supplements that include shiitake as one of a few ingredients — MGN-3, also known as BioBran, is a popular one for people with cancer.
What the research shows
There have only been a few small studies of shiitake in people with cancer, but the findings suggest that shiitake may boost cancer treatment while improving quality of life. (In studies, shiitake mushrooms are often referred to by their scientific name, Lentinula edodes.)
A sugar called lentinan gives shiitake most of its benefits. In some Asian countries, lentinan is given as an injection or IV alongside chemotherapy, but this isn’t approved in the United States and has different effects than taking shiitake as a supplement.
Immune response
There haven’t been many studies on shiitake in people with breast cancer, and those that have been done were small. (Results from smaller studies are generally less reliable than findings from larger studies.) Many of them do not use gold standard methods like randomly assigning people to either take shiitake or a placebo. But these studies suggest shiitake may help boost the immune system as people go through treatment.
Two very small studies found that taking shiitake extract during the second round of chemotherapy boosted the immune system of people with breast and gastrointestinal cancer. In both studies, people who took shiitake during the second round of chemo had a higher number of immune cells called natural killer cells, which directly target tumors, compared to the first round of chemo.
Other very small studies have found that taking shiitake daily can improve the immune function of people with advanced gastrointestinal cancer receiving chemotherapy, people with cancer receiving immunotherapy, and people with weakened immune systems receiving hormonal therapy after breast cancer surgery. In particular, it raises levels of an immune protein that can reduce cancer growth.
Quality of life
Several small studies have found that taking shiitake during cancer treatment may improve quality of life for people with breast cancer. In one study, 20 people with breast cancer received hormonal therapy after surgery for four weeks, then added 1800 mg of shiitake extract daily for eight weeks. When shiitake was added, their quality of life improved, including pain, energy, and social and physical functioning. Similar findings have been seen in small studies of people who took shiitake after receiving chemotherapy and immunotherapy.
Cell and animal studies
Studies in cells and animals are a key early step in research. But you can’t draw conclusions about how things will work in people based on these studies alone. For example, treating cells in a lab dish with shiitake extract won’t tell you how the human body absorbs shiitake or breaks it down. And cancer can behave differently in a mouse than it behaves in a person. These studies are valuable, though, because they help researchers find promising leads and decide if they should test these leads in people.
Lab studies in cells and animals have found that components of shiitake can slow tumor growth and trigger the death of breast cancer cells. They can reduce the spread of breast cancer cells (metastasis) and promote their breakdown without affecting healthy cells. They also affect cell signaling pathways and cancer genes. Shiitake has similar effects on other types of cancer cells as well.
MGN-3 and BioBran
A 2018 review of 11 studies suggests that MGN-3 may improve immune function in people with cancer. It may also enhance treatment outcomes, reduce side effects, and improve survival. It does not appear to cause side effects. But more research is needed to confirm these results. For now, there’s not enough research to recommend that people with cancer take MGN-3 or BioBran.
Safety, risks, and side effects
Shiitake is generally safe, but always talk to your doctor before starting a new supplement. Side effects of shiitake include rash and gastrointestinal symptoms, such as nausea and diarrhea. It can also raise the levels of white blood cells called eosinophils, which signals an allergy to shiitake and means you should stop taking it. There’s no standard dose of shiitake, so ask your health team to help you figure out how much to take.
Because shiitake boosts the immune system, people with autoimmune diseases or who are taking immunosuppressants shouldn’t use it.
Is it safe for people with breast cancer to take shiitake?
Early evidence suggests that shiitake may help to boost the immune system and improve quality of life in people undergoing cancer treatment. But more studies of people are needed to be sure. Because it’s generally safe, some people may consider taking shiitake in addition to cancer treatment. Always talk to your doctor before starting a new supplement.