I was introduced to the wonderful world of mushrooms after moving to Seattle over 10 years ago. Up until then, my experience of mushrooms consisted of the “canned variety” on pizzas and the occasional, negligible appearance in soups or salads. Sad, I know. Now, however, it is rare that I go longer than a few days without eating a meal including either culinary or medicinal mushrooms. It is a much better life healthier and tastier too! Mushrooms are a great addition to any nutritious diet but there is sometimes confusion regarding which types are both safe and offer health benefits.
ARE MUSHROOMS SAFE TO EAT?
The most common type of cultivated mushroom in North America is the Agaricus bisporus species. The white button mushroom, cremini and portabello are all different strains of this same species. Both wild and cultivated Agaricus genus mushrooms contain a naturally occurring phenylhydrazine derivative known as agaritine. Agaritine has been described in some studies as a potential carcinogen, however, feeding studies using mushrooms and mushroom extracts have in general provided no evidence of toxic effects of agaritine or mushroom consumption. The available evidence to date suggests that agaritine from consumption of cultivated Agaricus bisporus mushrooms poses no known toxic risk to healthy humans.
HOW STORAGE AND COOKING INFLUENCE AGARITINE CONTENT OF MUSHROOMS
Pronounced reduction in agaritine content was observed during storage of mushrooms in the refrigerator or freezer, as well as during drying of the mushrooms. Adding heat to mushrooms containing Agaritine before eating contributes to the prevention of any potential agaritine hazard. Depending on the cooking procedure, household processing of cultivated Agaricus mushrooms reduced the agaritine content to various degrees. One study found that boiling extracted around 50% of the agaritine content into the cooking broth within 5min and degraded 2025% of the original agaritine content of the mushrooms. Prolonged boiling, as when preparing a sauce, reduced the content in the solid mushroom further (around 10% left after 2h). Dry baking of the cultivated mushroom, a process similar to pizza baking, reduced the agaritine content by approximately 25%, whereas frying in oil or butter or deep frying resulted in a more marked reduction (3570%). Microwave processing of the cultivated mushrooms reduced the agaritine content to one third of the original level. Therefore, the exposure to agaritine was substantially less when consuming processed Agaricus mushrooms as compared with consuming the raw mushrooms.
Shiitake, Reishi, Turkey tail, Maitake, Oyster and Himematsutake are a few types of medicinal mushrooms that are worth including in one’s diet. A total of 126 medicinal functions are thought to be produced by medicinal mushrooms and fungi including antitumor, immunomodulating, antioxidant, radical scavenging, cardiovascular, anti-hypercholesterolemia, antiviral, antibacterial, antiparasitic, antifungal, detoxification, hepatoprotective, and antidiabetic effects.
Mushrooms are a good source of antioxidants including selenium which plays a role in liver enzyme function, and helps detoxify some cancer causing compounds in the body. Selenium is also an anti-inflammatory that can decrease tumor growth rates. The vitamin D in mushrooms has also been shown to inhibit the growth of cancer cells by contributing to the regulation of the cell growth cycle. The folate in mushrooms plays an important role in DNA synthesis and repair, thus preventing the formation of cancer cells from mutations in the DNA.
Mushrooms of the genus Agaricus are a common folk remedy against cancer. The active ingredients, polysaccharides and protein-polysaccharide complexes containing beta-glucan, have been isolated and shown to have indirect tumor-suppressing activity via an immunological activation. Agaritine from Agaricus blazeiMurrill, a Brazilian species, has direct antitumor activity against leukemic tumor cells in vitro. This is in contrast to the carcinogenic activity previously ascribed to the compound. One study has shown that this activity is mediated through apoptosis or programmed cell death. This is distinct from the activity of beta-glucan, which indirectly suppresses proliferation of tumor cells.
Consuming mushrooms, which are high in potassium and low in sodium, helps to lower blood pressure and decrease the risk of high blood pressure and cardiovascular diseases. Extracts from oyster, shiitake, maitake, white button mushrooms and cremini mushrooms have been found to reduce the binding of certain immune cells onto the lining of the aorta. When mushrooms reduce this binding, they also lower risk of damage to the aorta and risk of blood flow problems. Their antioxidant capacity also helps to reduce oxidative stress that can cause damage to blood vessels and contribute to atherosclerosis. Additionally, an intake of 3 grams of beta-glucans per day can lower blood cholesterol levels by 5%.
Selenium has also been found to improve immune response to infection by stimulating production of killer T-cells. The beta-glucan fibers found in the cell walls of mushrooms stimulate the immune system to fight cancer cells and prevent tumors from forming. In a recent study, 52 healthy adults were given a 4 oz serving of shiitake mushrooms to eat daily and in 4 weeks, their blood tests revealed improved functioning of immune cells (T-cells) and decreased inflammatory proteins.
Mushrooms contain two types of dietary fibers in their cell walls: beta-glucans and chitin which increase satiety and reduce appetite, which increases satiety and thereby lowers overall calorie intake. One study found that substituting red meat with 1 cup of white button mushrooms helped enhance weight loss. At the end of the 12month trial, the intervention group had also showed improvements in body composition, such as reduced waist circumference, and ability to maintain their weight loss, compared to the control group.
Other Nutritional Benefits
Mushrooms are rich in B vitamins such as riboflavin, folate, thiamine, pantothenic acid, and niacin. They are a good source of vitamin D and also provide several minerals such as selenium, potassium, copper iron, and phosphorus.
Beta-glucans are a type of fiber that is found in the cell walls of many types of mushrooms. Recently, beta-glucans have been the subject of extensive studies that have examined their role in improving insulin resistance and blood cholesterol levels, lowering the risk of obesity and providing an immunity boost.
Mushrooms also contain choline; an important nutrient found that helps with sleep, muscle movement, learning and memory. Choline assists in maintaining the structure of cellular membranes, aids in the transmission of nerve impulses, supports proper fat absorption and reduces chronic inflammation.
Most mushrooms are bought at grocery stores or farmer’s markets but some choose to forage for their own wild mushrooms. This can be as fun and interesting as it can be dangerous if one does not have adequate training in mushroom identification. There are poisonous and even deadly mushrooms. The North American Mycological Association receives an average of one report of a human death due to mushrooms each year. It is not dangerous to touch poisonous mushrooms but it is safest to only eat mushrooms that can be identified with 100% certainty and never raw. The Puget Sound Mycological Society is a great resource for budding mushroom enthusiasts. Happy hunting!
Current findings, future trends, and unsolved problems in studies of medicinal mushrooms. Wasser SP1. 2011
Agaritine from Agaricus blazei Murrill induces apoptosis in the leukemic cell line U937. Akiyama H1 et al 2011
Dr. Adeola Mead, ND is the Natural Choice Network's Healthy Living Content Coordinator. She is a naturopathic physician with a clinical focus on women's health and stress-related illness. Dr. Mead is passionate about using natural medicine education as a powerful healing tool for both individuals and communities.