Could the fungus among us be hiding important and rare phytonutrients?
Most famous of the fungal world, mushrooms have long been appreciated for certain health benefits. Among the many safe-to-eat mushrooms, there are some mushrooms that have been traditionally used as medicines and folk remedies. Mushrooms are biologically distinct from all other plant foods including fruits, vegetables, and grains, and therefore offer a different array of phytonutrients. These unique qualities are why medicinal mushrooms are a major cornerstone of Traditional Chinese Medicine and other forms of Eastern medicine, which have used medicinal mushrooms as natural remedies for everything from adrenal support to cancer treatment. More recently, medicinal mushrooms have come to be recognized as natural agents that may be used in the prevention and even treatment of many diseases including cancer, cardiovascular disease, diabetes, and neurodegenerative diseases.1 Despite being used for millennia, exactly how medicinal mushrooms affect the body and promote health is only beginning to come to light.
Nutrient Profile and Antioxidant Activity
Medicinal mushrooms provide important key nutrients including B vitamins, selenium, copper, and potassium. They are also one of the few natural food sources of vitamin D2, although the actual vitamin D2 content will vary according to exposure to sunlight.2 The health benefits of mushrooms are due in part to their contribution of vitamins and minerals to the diet, but much of the emerging research focuses mainly on other bioactive compounds that mushrooms offer, such as polyphenols, carotenoids, lycopene, polysaccharides, and a rare type of amino acid.3 In the digestive tract, mushroom polysaccharides act as a prebiotic substrate for intestinal microbes, making them beneficial for gut health.
Mushrooms have been shown to have potent antioxidant activity, much of which is attributed to its polysaccharides, though its lycopene and polyphenol content appear to be strongly correlated with free radical scavenging activity.4 Mushroom polysaccharides have been observed to have an antioxidant effect by quenching free radicals. In animal studies, they were found to inhibit cancer cell proliferation. The selenium and zinc found in mushrooms may further increase mushrooms’ antioxidant effect. Selenium- and zinc-enriched mushrooms have been found to improve glutathione peroxidase and superoxide dismutase activity in mice, which substantially increased their antioxidant capacity.5
While mushrooms’ antioxidant activity is an essential component of their healing properties, polysaccharides in mushrooms also offer a host of potential health benefits, the most well studied being beta-glucan.
Many of medicinal and edible mushrooms’ health benefits have been attributed to the actions of specific polysaccharides, long chain carbohydrates held together by glycosidic bonds. The two main types of mushroom polysaccharides under investigation include beta-glucans and polysaccharide-protein complexes, and their most promising potential benefits include immunomodulation and anti-cancer effects. In vivo and in vitro research suggests that polysaccharides and polysaccharide-protein complexes act as “biological response modifiers,” with the ability to modulate the gene expression of various immune-modulating cytokines and cytokine receptors. This type of action may result in the activation of different kinds of immune cells that are important for maintaining homeostasis and cancer prevention.6
The Immunomodulatory Effects of Mushrooms
Medicinal mushrooms may support and increase the activity of:7
- Spleen lymphocytes
- Natural killer cells
- Th1 lymphocytes
- Macrophage metabolism
- Lymphocyte proliferation
- Antibody production
- Macrophage multiplication
Mushroom polysaccharides appear to indirectly modulate immune function, stimulating both the innate and adaptive immune system, rather than having a direct cytotoxic effect on cancer cells.8 They have been found to trigger a variety of cellular responses that enhance immune function. Polysaccharides are considered multi-cytokine inducers, triggering the expression of signaling proteins like interleukins and interferon,9 as well as nitric oxide synthesis.10 Beta-glucans may also increase immune defense through the activation of T-cells, natural killer cells, and macrophages, enhancing their anti-tumor activity.11 These combined actions may allow the body’s immune system to better combat the effects of cancer cells.
Mushroom beta-glucans may also combat tumor-induced immune suppression, a major problem in cancer immunotherapy. Myeloid-derived suppressor cells (MDSCs) are undifferentiated cells generated in bone marrow. In healthy individuals, MDSCs quickly become dendritic cells, macrophages or granulocytes. But when tumors are present, conversion of MDSCs are blocked and remain myeloid cells, which accumulate and suppress the immune system. Beta-glucans may prevent MDSC-mediated immunosuppression by promoting the differentiation of MDSCs, which may provide a clinical benefit in cancer treatment.12
Mushrooms have shown an inhibitory effect against certain cancers, including cancers of the breast, liver, cervix, pancreas, and stomach as well as acute leukemia.13 Beta-glucans derived from reishi and other mushrooms have been found to inhibit the proliferation of certain breast cancer lines through the induction of apoptosis and cell-cycle arrest, and meta-analyses have found an inverse relationship between eating mushrooms and breast cancer.14 Animal studies have suggested that mushroom extracts inhibit aromatase activity, reducing circulating estrogen, which may provide a benefit against estrogen receptor-positive tumors.15
While it’s clear that beta-glucans and polysaccharide-protein complexes offer exciting potential benefits, an unusual amino acid found in mushrooms may be the next phytonutrient to watch.
The Elusive Ergothionine: A New Vitamin?
Ergothionine (ET) is a unique sulfur containing amino acid synthesized from histadine by mycobacteria and non-yeast fungi in the soil. It is found in very few foods, yet is highly concentrated in mushrooms. Recently, it was discovered that all mammals have a highly specific transporter molecule for ET, which suggests that this amino acid has a very important physiological role. In fact, when researchers depleted cells of ET transporters, they found that the cells were much more susceptible to oxidative stress, mitochondrial DNA damage, protein oxidation, and lipid peroxidation. Because ET transporters are most concentrated in mitochondria, it is believed that ET likely protects cells and DNA from oxidative damage and the effects of mitochondria-generated superoxide. In fact, ET may be as potent as glutathione as an antioxidant.16
Since mammals cannot synthesize ET and can only get it from food, and a lack of ET appears to have significant consequences, some researchers have proposed categorizing ET as a new vitamin.17 From this perspective, ET can certainly be considered an essential nutrient that underscores mushrooms’ contribution to a healthy diet.
Mushrooms as an Anti-Fungal
Fungal dysbiosis and fungal overgrowth in the digestive tract is a common health issue that integrative practitioners encounter, and it is typically treated with a combination of anti-fungal herbs and a low-yeast diet. Whether mushrooms should be permitted in low-yeast or anti-candida diets is an ongoing topic of debate. Despite mushrooms being fungi, certain mushrooms have been found to have antimicrobial and antifungal properties, particularly shiitake and oyster mushrooms.18 In fact, extracts of Agaricus bisporus mushrooms, better known as white button, crimini, and Portobello mushrooms, were found to have antifungal activity against Candida yeast species.19
Patients with systemic fungal infections have been observed to have higher levels of circulating beta-glucans. It has been suggested that beta-glucans may modulate the immune system in response to Candida albicans and other common fungal infections by activating macrophages, increasing phagocytosis, and modulating proinflammatory cytokines to combat fungal infections.20
These studies suggest that mushrooms may be a helpful addition to low yeast and anti-candida diets, and advising against eating mushrooms to those with fungal overgrowth may be counterproductive.
Important Mushrooms to Know
• Shiitake mushrooms (Lentinula edodes) are the most studied mushrooms species and have a long history of medicinal use, due to their many potential benefits from cancer protection to cholesterol reduction. Shiitake mushrooms have been found to possess anti-cancer benefits, and they may modulate the immune system by increasing the generation and activity of both helper T cells and cytotoxic T cells. Shiitake extracts have even been used as an adjunct therapy to chemotherapy and radiation. Considered a potent anti-microbial, eating shiitake mushrooms may offer enhanced resistance to bacterial, fungal, parasitic, and viral infections.21
• Maitake mushrooms (Grifola frondosa), also called “hen of the wood” mushrooms, are especially sought after for their taste and texture. Maitake mushrooms have been found to protect against metastasis and may slow or stop the growth of tumors. They also may support lymphocyte and natural killer cell activity. Maitake mushrooms given in supplement form were found to significantly attenuate side effects of chemotherapy, including loss of appetite, vomiting, nausea, hair loss, pain, and leukopenia.22
• Turkey tail mushrooms (Coriolus versicolor), also referred to as “cloud mushrooms,” are the source of the first mushroom-based cancer drug, still in use in Japan for gastric and other cancers. Polysaccharides from turkey tail mushrooms may inhibit the proliferation of cancer cells, including human hepatic cancer cells, and may also help to mitigate the toxic effects of cancer treatment.23
• Reishi mushrooms (Ganoderma lucidium) are commonly used as an adrenal adaptogen. These mushrooms are also regarded as important natural immunomodulators, and a good source of selenium. Reishi mushrooms may be helpful in the treatment of bladder cancer and may protect the liver from exposure to toxic chemicals. In Asia, reishi mushrooms are used to treat chronic infections like hepatitis and bronchitis, as these mushrooms have demonstrated a broad range of antibacterial and antiviral activity. In fact, high-dose reishi supplementation was observed to improve hepatitis B levels in infected patients in a double-blind, randomized, placebo-controlled study.24,25
• Cordyceps (Cordyceps militaris and Cordyceps sinensis) mushrooms are also typically used as adrenal adaptogens as well as for immune support and are considered one of the most valuable medicinal mushrooms in China. These mushrooms possess potent antioxidant activity and have been found to have anti-tumor and antiproliferative effects. Aside from its potential anti-cancer and immune-modulating activity, C. militaris has been found to be effective against infections like chronic bronchitis, influenza A and viral infections. C. sinensis may improve oxygen utilization, ATP production and blood sugar metabolism. Other studies have shown cordyceps to have antibacterial properties, reduce asthma, lower blood pressure, and may have a protective effect on the liver, heart and kidneys.26,27
Biologically distinct from all other foods, edible and medicinal mushrooms offer a wide range of important health benefits. While they are rich in vitamins, minerals and phytonutrients, it is their unique combination of polysaccharides and a rare amino acid that have researchers and health practitioners interested in mushrooms, ensuring that these fungi retain their rightful place in practitioners’ natural healing toolbox.