The Mushrooming Health Benefits of Fungi

Consumption of mushrooms in the United States has steadily increased over the past several decades. Americans consume nearly 4 lb/person/year.

China accounts for 32% of the world’s mushroom production, followed by the U.S. with 16%. The white button mushroom, Agaricus bisporus, is the most widely cultivated species worldwide and the most commonly consumed in the U.S. Its production has increased by approximately 12% over the past decade.

Mushrooms provide many desirable characteristics as food, including the flavor-promoting quality of umami, which stimulates a meaty, savory effect. On a fresh-weight basis, mushrooms contain approximately 90% moisture. They are low in carbohydrates, fat, sodium, and calories. Recently completed research conducted at Johns Hopkins Bloomberg School of Public Health (Cheskin et al., 2007) found that substituting the white button mushroom for meat entrees provided an acceptable lower-calorie alternative without compromising flavor or satiety.

Depending on the species, mushrooms provide numerous vitamins, including thiamin, riboflavin, niacin, pantothenic acid, and biotin, as well as substantial amounts of potassium, phosphorus, magnesium, copper, and selenium. Preliminary evidence indicates that they have the potential to produce substantial amounts of vitamin D₂ by being exposed to ultraviolet light during growth.

China and Japan have long recognized the nutritional and medicinal properties of various genera and species of mushrooms. Generally, mushrooms are a valuable source of bioactive agents that demonstrate different medicinal properties. In-vitro and in-vivo studies have shown an array of beneficial biological effects (Chang and Buswell, 2003). However, despite their historical usage in traditional chinese medicine, there are no epidemiological studies to support the health benefits of consuming mushrooms.

Mushrooms represent an area of intense research for functional and nutritional components. Dubost et al. (2007) at Penn State University recently identified and quantified one particular antioxidant, ergothioneine, that is predominately produced by fungi. Also known as 2-mercapto-L-histidine betaine, ergothioneine is not synthesized in humans. Blood levels of ergothioneine increase after incorporation into the diet. These levels vary among individuals, yet its distribution is similar, predominately in erythrocytes, bone marrow, seminal fluid, and ocular tissue.

In-vitro studies at Penn State suggest that ergothioneine is a strong scavenger of oxidants and chelator of various divalent metallic cations. Other functions of ergothioneine in vivo include retarding lipid peroxidation, protecting erythrocytes, and exhibiting anti-inflammatory properties. Recently, the researchers discovered an ergothioneine transporter highly specific for its physiological substrate ergothioneine.

Mushrooms serve as one of the best sources of ergothioneine, providing up to 13 mg/85-g serving of specialty mushrooms and up to 5 mg/serving of A. bisporus—white button, crimini (brown button), or portabella. Because of the concentration of ergothioneine in mushrooms, researchers speculate that consumption of mushrooms may provide strategy for modulating inflammatory responses.

In addition to quantifying ergothioneine in mushrooms, the Penn State researchers also showed that of the specialty mushrooms, the white button, crimini, and portabella mushrooms provided the highest total antioxidant capacity and total polyphenol content. Based on the total polyphenol analysis, the most commonly consumed mushrooms provide up to 75 mg/serving. However, it is important to remember that these antioxidant assays do not determine biological activity, and the clinical significance of these polyphenols from mushrooms remains to be determined.

Mushroom polysaccharides, particularly beta-glucans, have been purported to provide immunomodulatory effects, as well as hypocholesterolemic effects. An in-vivo study by Wu et al. (2007) indicated that consumption of white button mushrooms may increase innate immunity, particularly against tumors and viral infections in mice through IFNγ and TNFα production.

Overall, the science behind the health benefits of mushrooms is emerging. Further clinical evidence is needed to determine the exact biological relevance, along with mechanisms of action of the various bioactive agents. The historical and 21st-century evidence suggests that consuming a variety of mushrooms may provide an array of benefits ranging from sensory to health.

References for the studies mentioned above are available from the authors.

by Roger Clemens, Dr.P.H.,
Contributing Editor
Special Projects Advisor, ETHorn, La Mirada, Calif. 
[email protected]

Joy Dubost, Ph.D., R.D.
Principal Nutritionist,
Pepsi-Cola Co., Valhalla, N.Y. 10595.
[email protected]