Eating around 18 grams of mushrooms a day, roughly an eighth to a quarter of a cup, was associated with a 45 percent lower risk of cancer compared with people who ate none. That is the headline finding from a systematic review and meta-analysis by researchers at Penn State that pooled 17 observational studies published between 1966 and 2020 and covered more than 19,500 cancer patients.
The association held across mushroom varieties and was strongest for breast cancer. The work was published in the journal Advances in Nutrition in 2021.
Researchers point to ergothioneine, an amino acid and antioxidant that humans cannot make on their own. Mushrooms are its richest known food source.
"Mushrooms are the highest dietary source of ergothioneine, which is a unique and potent antioxidant and cellular protector," said Djibril M. Ba of Penn State College of Medicine, the study's lead author.
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Because the underlying studies are observational, they can only show an association, not prove that mushrooms themselves cause the lower risk. Still, the pooled signal across nearly 55 years of data is what gives the finding weight.
What mushrooms may do for the brain
A separate six-year study from the National University of Singapore followed more than 600 Chinese seniors aged 60 and older and tracked their diets and cognition. Participants who ate more than two portions of mushrooms a week, about one and a half cups of cooked mushrooms, had roughly 50 percent lower odds of mild cognitive impairment, the memory and thinking problems that can precede dementia.
"This correlation is surprising and encouraging. It seems that a commonly available single ingredient could have a dramatic effect on cognitive decline," said Assistant Professor Feng Lei of NUS Psychological Medicine, the lead author, in the university's announcement of the work in the Journal of Alzheimer's Disease.
Even a single small portion a week appeared to help, the researchers noted. The mushrooms in the study included golden, oyster, shiitake, white button, and dried and canned varieties.
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A possible link to mood
A separate analysis of nearly 24,700 US adults from the National Health and Nutrition Examination Survey found that mushroom eaters had lower odds of depression than people who did not eat them, even after adjusting for other diet and lifestyle factors. The work was published in the Journal of Affective Disorders in 2021 and also led by Ba at Penn State.
The proposed mechanism is again ergothioneine, which may lower oxidative stress in the brain. Interestingly, more mushrooms did not mean lower risk in a straight line. Higher intake did not add extra benefit in this dataset.
Gut, vitamin D and immunity
Mushrooms also contain polysaccharides that act as prebiotics. According to UCLA Health, these compounds pass through the stomach unchanged and reach the colon, where they encourage the growth of beneficial bacteria.
They are also the only produce that naturally provides vitamin D, and white button, portabella and cremini varieties can build up more of it after exposure to UV light or sunlight. Selenium, vitamin D and vitamin B6 in different varieties support immune function.
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Cedars-Sinai describes ergothioneine as a "longevity nutrient" and notes it is most concentrated in shiitake, oyster and maitake mushrooms. The medical center also flags that the same polysaccharides linked to gut bacteria have been associated with improved insulin sensitivity.
What a sensible serving looks like
The takeaway from the research is not a supplement bottle. It is food. The Penn State numbers point to a modest daily amount, an eighth to a quarter cup, and the Singapore work suggests roughly two portions across the week. Varying the type, including shiitake, oyster or maitake for higher ergothioneine, may be a reasonable way to eat for the compounds researchers are interested in.
None of this replaces medical care. Anyone with concerns about cancer risk, memory changes or persistent low mood should speak with their doctor.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.