Berries and other colorful plant foods provide antioxidants in abundance.
Mushrooms also contain antioxidants, but new findings reveal that certain kinds provide high levels of two uncommon, exceptionally healthful antioxidants.
We already knew that mushrooms provide fiber, vitamin D2, and immune-boosting compounds such as alpha- and beta-glucans.
And mushrooms — which offer a wide range of flavors, colors, and textures — expand the possibilities and attractions of any daily menu.
Before we get into the new research, let's quickly review what's known about free radicals, antioxidants, and their effects on human health.
What are free radicals and antioxidants?
When we digest and metabolize food to produce energy, this process generates unstable oxygen atoms call free radicals or oxygen radicals.
Free radicals are also generated by chronic inflammation, by manmade pollutants in air, food, and water, and by the immune system as a weapon against infectious pathogens.
The electrons that orbit atoms normally occur in pairs, and the loss of one electron prompts an atom to try to replace it.
Free oxygen radicals have an unpaired electron, so they try to steal one from nearby atoms or molecules — thefts that can damage our cells, proteins, and DNA.
Antioxidants work by donating an electron to a free radical, thereby stabilizing or "neutralizing" it.
Whenever a large burden of free radicals in the body overwhelms its antioxidant defenses, the resulting “oxidative stress” disrupts basic cellular functions, promotes inflammation, and raises the risks for cancer and chronic heart, brain, immune, and diabetic disease.
The body’s “antioxidant network” — which it uses to control free radicals — consists partly of internally produced compounds, including enzymes, lipoic acid, CoQ10, and others.
But that network also relies on dietary antioxidants like vitamin C, vitamin E, carotenoids, and polyphenols.
Diets higher in these foodborne antioxidants appear to reduce the damage caused by excess free radicals, thereby slowing aging, and diminishing the risk for chronic diseases.
How do dietary antioxidants help?
The vitamin C in foods or supplements can directly neutralize free radicals and reduce oxidative stress.
In contrast, the polyphenol antioxidants in berries, greens, raw cocoa, and other colorful foods dampen oxidative stress and inflammation indirectly, by influencing our “working” genes.
Berries, dark leafy greens, carrots, apples, pomegranate, and other colorful fruits and vegetables get most of the attention when it comes to the benefits of dietary antioxidants.
Indeed, population studies generally link diets rich in fruits and veggies to reduced risk for chronic conditions like cancer, cardiovascular disease, diabetes, and Alzheimer's.
But a new study from the University of Pennsylvania places mushrooms high on the antioxidant pedestal, revealing that they provide unusually high levels of two particularly beneficial antioxidants.
Before we examine those exciting findings, let’s look at a prior, stage-setting mushroom study from the same Pennsylvania team.
Mushrooms found to rival colorful veggies in 2006 study
University of Pennsylvania professor Robert Beelman’s laboratory specializes in examining the nutritional and antioxidant content of foods.
About 10 years ago, a doctoral candidate in Beelman’s lab — N. Joy Dubost — measured the activity of two classes of antioxidants, polyphenols and ergothioneine, in mushrooms.
She used a measure of antioxidant capacity called the ORAC assay — a test-tube procedure that measures the effect of a food or individual food compound on free radicals, with a higher ORAC score indicating greater antioxidant capacity.
Dubost found that crimini mushrooms score 9.5 on the ORAC scale, while portabella mushrooms score 9.7 — compared with carrots and green beans at 5, red peppers at 10, and broccoli at 12.
The ORAC assay cannot predict how a foodborne antioxidant would affect free radical levels in the human body.
But the rankings obtained by a newer test called the CAA assay — which measures the actual effects of a food or its isolated antioxidants inside live cells — often validate the predictive value of a food's ORAC score.
In other words, foods that rank high on the ORAC assay also tend to rank high on the CAA assay — which means that foods or isolated antioxidants that score high on the ORAC scale are likely to deliver real health benefits (see Starch Fuels Aging... Fruits and Veggies Fight Back and Wild Blueberries Reclaim Antioxidant Crown).
New study puts mushrooms on an even higher antioxidant pedestal
Last month, Professor Beelman’s team published the results of a follow-up study that make mushrooms look even better (Kalaras MD et al. 2017).
In short, their findings revealed that certain mushrooms provide extraordinarily high amounts of two antioxidants that could help fight aging and bolster health, called ergothioneine and glutathione.
Those two key antioxidants — which the body produces internally — are either absent from fruits and vegetables, or only occur at low levels.
The University of Pennsylvania team tested 13 species, and found that certain mushrooms provide amounts of ergothioneine and glutathione unmatched by other plant foods.
“We found 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,” said Beelman.
In fact, mushrooms high in glutathione also ranked high for ergothioneine content, and vice versa.
The amounts of the two compounds varied greatly between mushroom species, and Beelman's team found that one species — a wild variety — contained the highest levels of both antioxidants.
"We found that the porcini has the highest [levels of ergothioneine and glutathione], by far, of any we tested," said Beelman. “This species is really popular in Italy where searching for it has become a national pastime.”
(Porcinis, pictured at right, are readily available in stores.)
However, oyster, shiitake, and maitake mushrooms were also quite high in the two antioxidants.
White button, crimini, baby bella, and portabella mushrooms — the best-selling varieties in the U.S. — had the lowest levels of these antioxidants, but they still had more than most fruits or vegetables.
NOTE: All of these mushrooms are the same species, called Agaricus bisporus. Portabellas are simply larger, fully mature criminis, baby bellas are another name for criminis, and criminis are simply a slightly different strain of the species, colored brown rather than white.
Don't dismiss everday mushrooms
Even commonplace Agaricus bisporus mushrooms (white button/crimini/portabella) may provide serious health benefits.
For one thing, the Pennsylvania team's 2006 study found that these familiar mushrooms rank pretty high on the ORAC antioxidant-capacity scale.
And Beelman’s team published a study last year in which they reported detecting “significant beneficial health effects” in people with type II (adult onset) diabetes who consumed 3.5 ounces (100gm) of white button mushrooms daily for four months (Calvo MS et al. 2016).
Specifically, eating white button mushrooms doubled the participants’ blood levels of ergothioneine, raised the antioxidant capacity of their blood, raised their blood levels of the anti-inflammatory hormone adiponectin, and significantly reduced markers for oxidative stress.
As Beelman’s group wrote, “We conclude that WBM [white button mushrooms] contain a variety of compounds with potential anti-inflammatory and antioxidant health benefits that can occur with frequent consumption over time in adults predisposed to diabetes.”
What do the Pennsylvania findings mean for human health?
Last year, Singapore-based researchers found that blood levels of ergothioneine (ET) decline significantly after age 60, and that older people with mild cognitive impairment have significantly lower blood levels, compared with brain-healthy people of the same age (Cheam IK et al. 2016).
As the Singapore team wrote, “This decline suggests that deficiency in ET may be a risk factor, predisposing individuals to neurodegenerative diseases.”
And earlier this year, the Singapore team found that people who took supplemental ergothioneine displayed lower levels of oxidative damage and inflammation (Cheam IK et al. 2017).
Dr. Beelman pointed to preliminary research showing 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.”
Beelman cautioned that we don’t yet know whether that link is just a correlation, or reveals that these mushrooms are directly responsible for lower rates of these brain diseases.
“But”, as Beelman said, “it's something to consider, because the difference between the countries with low rates of neurodegenerative diseases is about 3 milligrams [of these mushroom-borne antioxidants] per day, which is about five button mushrooms each day.”
He expressed hope that other researchers will look for links between the amounts of dietary ergothioneine and glutathione in people’s diets and their risk for neurodegenerative diseases.
Which cooking method preserves mushrooms antioxidants the best?
The Pennsylvania group reported that cooking mushrooms didn’t significantly affect their levels of ergothioneine and glutathione.
However, cooking method may matter to retention of other antioxidants.
Earlier this year, Spanish researchers tested the effects of different cooking methods on the antioxidant capacity of mushrooms, and came to these conclusions:
“A significant decrease was detected in the antioxidant activity after boiling and frying, while grilled and microwaved mushrooms reached higher values of antioxidant activity.” (Ron cero-Ramos I et al. 2017)
The bottom line: Put mushrooms on your menu
Given the suggestive links between mushrooms and better brain and metabolic health, it makes sense to enjoy more mushrooms — especially the varieties highest in antioxidants.
Our recipe archive provides several recipes featuring mushrooms, and you can find all recipes with mushrooms by searching our website for “mushrooms”.
These are some of our favorites:
Wild seafood recipes with mushrooms
Grass-Fed beef recipes with mushrooms