Widely varying contents of both glutathione (GSH) and ergothioneine (ERGO) were measured in analysis of numerous species of mushroom conducted by researchers from Penn State University.
Maitake contained the highest amount of GSH (2.41 milligrams/ gram dry weight (mg/g dw), while porcini (7.27 mg/g dw) was richest in ERGO.
"What we found is that, without a doubt, mushrooms are [the] highest dietary source of these two antioxidants taken together, and that some types are really packed with both of them," commented lead researcher Robert Beelman, emeritus professor of food science and director of the Penn State Centre for Plant and Mushroom Products for Health.
For ERGO, "We found that the porcini has the highest, by far, of any we tested," said Beelman. "This species is really popular in Italy where searching for it has become a national pastime."
Common varieties such as white button and portobello mushrooms contained lower amounts of the two antioxidants than most of the wild species. However, surprisingly, chanterelles - a wild variety in high demand as a culinary delicacy – had the lowest contents of both nutrients.
The scientists also discovered that GSH and ERGO contents within a given species were highly correlated.
The study is believed to be the first of its kind in evaluating the GSH content of mushroom varieties. The findings could eventually lead to anti-ageing treatments and strategies based on the two antioxidants.
GSH, ERGO and health
Glutathione is an intracellular antioxidant widely recognised for its ability to maintain immune function, detoxify carcinogens and other toxins. Optimum tissue levels of gluthathione are known to be essential in maintaining health and preventing diseases.
“GSH plays a critical role as the master antioxidant in mammalian cells and tissues and dietary intake of GSH has been identified as an important source of GSH for the body,” wrote the researchers.
While the exact role of ergothioneine is unclear, previous research has suggested it may help maintain glutathione levels through interaction with other cellular defence systems.
Studies in mice have shown a protective effect of ERGO against beta-amyloid plaque accumulation, while some epidemiological trends also suggest ERGO intake may be linked to lower risk of cognitive decline.
"It's preliminary, but you can see that countries that have more ergothioneine in their diets, countries like France and Italy, also have lower incidences of neurodegenerative diseases, while people in countries like the United States, which has low amounts of ergothioneine in the diet, have a higher probability of diseases like Parkinson's Disease and Alzheimer's," said Beelman.
"Now, whether that's just a correlation or causative, we don't know. But, it's something to look into, especially because the difference between the countries with low rates of neurodegenerative diseases is about 3 milligrams per day, which is about five button mushrooms each day."
Importantly, the mushrooms appear to retain their antioxidant content when cooked.
The researchers advocate that further studies are warranted to assess the health benefits of mushroom consumption.
“Based upon the very high levels of both ERGO and GSH, mushrooms clearly represent a uniquely rich dietary source for antioxidants. Given the important role of oxidative stress in disease development and the aging process itself and the well-known protective roles of antioxidants, mushrooms could play a protective role,” they conclude.
Source: Food Chemistry
Volume 233, pp 429-433. DOI: 10.1016/j.foodchem.2017.04.109
“Mushrooms: A rich source of the antioxidants ergothioneine and glutathione”
Authors: Michael D. Kalaras, John P .Richie, Ana Calcagnotto, Robert B. Beelman