A recent meta-analysis of 17 observational studies found an association between increased mushroom consumption and a lower risk of cancer. In participants who ate 18 grams (g) of mushrooms daily, the meta-analysis found a 45% lower relative risk of cancer, compared to participants who did not eat mushrooms.
Potentially preventable risk factors, such as smoking, being overweight, poor diet and excessive sun exposure, are associated with many cancers.
Free radicals, which are formed in the body during many cellular processes, are extremely reactive substances which, in high concentrations, can potentially damage cells. DNA damage caused by free radicals can contribute to the development of cancer.
Dietary factors account for about 4% of all cancer cases. Diets including fruits, vegetables, whole grains, fish, poultry, and fewer red and processed meats are associated with lower cancer risk. Fruits, whole grains and vegetables are sources of antioxidants. Antioxidants neutralize free radicals in the body, preventing damage. Although the body produces some antioxidants internally, it depends primarily on those obtained from food.
Mushrooms: A Food Source Rich in Antioxidants
Mushrooms are rich in fiber, vitamins, minerals and antioxidants. They are excellent dietary sources of two antioxidants: ergothioneine and glutathione.
In particular, ergothioneine could have a protective role against cancer. Ergothioneine concentrations differ depending on the type of mushroom, with oyster mushrooms, shiitakes, maitakes, and king oyster mushrooms having higher concentrations than creminis, portobellos, or button mushrooms.
Previous laboratory studies have shown that mushrooms have anti-cancer effects. However, previous observational studies have shown mixed results, with some demonstrating a decrease in cancer risk with increased mushroom consumption, while others have found non-significant correlations.
A previous meta-analysis that examined the association between cancer risk and mushroom consumption was limited, including only seven studies and only looking at breast cancer risk. This prompted researchers at Penn State College of Medicine and Pennsylvania State University to conduct a more comprehensive systematic review and meta-analysis of observational studies. The researchers published their findings in the journal Nutrition. The new meta-analysis included 17 observational studies published between January 1, 1966 and October 31, 2020, with 11 case-control study designs and six cohort study designs. Outcomes examined included total cancer risk and site-specific cancer risk.
Reduced risk of associated cancer
The researchers found a 34% decrease in the relative risk of cancer between the groups that consumed the most mushrooms and those that consumed the least. The associated relative risk of cancer was 45% lower between people consuming 18 g of mushrooms per day and those not consuming any. When examining site-specific cancer associations, the meta-analysis only found a significant pooled relative risk reduction of 35% for breast cancer.
According to the researchers, the strengths of their meta-analysis are the inclusion of studies that explored the risk of multiple types of cancer, the majority of them using validated dietary assessment methods.
The results of this study may provide a springboard for further exploration of the protective effects of mushrooms and their potential role in cancer prevention. Future research is needed to explore the underlying mechanisms and the extent to which mushrooms may have this effect.
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Mushrooms: A rich source of the antioxidants ergothioneine and glutathione
