Much Ado About Mushrooms by Christina Badaracco, MPH, RD
Populations around the world have eaten cultivated mushrooms for many centuries and wild mushrooms surely for even longer. Edible mushrooms have traditionally been used for medicinal purposes in much of the East, but only recently have Western countries been interested in harnessing the known health benefits of edible mushrooms as supplements. Determining and communicating the evidence behind the growing mushroom fad is an essential step in ensuring the merit of the new trend.
How are mushrooms grown?
Although commonly eaten as vegetables, mushrooms are actually edible fungi. Rather than conducting photosynthesis to make food for themselves, they use fibers called hyphae—together called a mycelium—to take in nutrients from their immediate environment. These can remain dormant when not needed, but they can also develop into structures that reproduce spores through asexual reproduction during the growing season. The mature fruiting body, consisting of cap and stalk, appears above ground and produces and disperses spores from under its cap (see figure below).
Mushroom growth depends upon the decomposition of nutrient-rich compost or substrate in a humid environment. But while they are fueled by decomposition, mushrooms play a critical role in nature's ongoing rebirth. When cultivated, a mycelium is placed on a substrate, which may be a log or a tray. It then grows spores through inoculation. After a period of propagation and possibly fertilization, mushroom “pins” will begin to mature and can be harvested in cycles. Climactic conditions are closely controlled to optimize growth. About 14% of mushroom production by weight is organic. They don’t contain dangerous pesticide residue levels and are listed on the Environmental Working Group’s Clean Fifteen list.
Mushrooms foraged in the wild may grow on trees, soil, logs or even other mushrooms. Morels, chicken-of-the-woods and truffles are a few of the highly prized mushrooms typically only found through foraging.
China, Italy and the US are the world’s top producers of mushrooms, with China producing more than 5 million tons per year. Global production has increased steadily over the last several decades. Mushrooms in the Agaricus genus—including white button, portobello and crimini—accounted for 93% of sales of cultivated mushrooms, while the remainder are deemed “specialty mushrooms.”
How are mushrooms eaten?
The roughly 2,000 varieties of edible mushrooms may be either cultivated or harvested in the wild. White button mushrooms are most common, accounting for about 90% of US consumption.
Mushrooms may be consumed whole as foods—either raw or cooked—or in supplemental forms. They are popular in dishes such as chicken Marsala and stuffed mushroom caps. They can be integrated into foods traditionally made of pure red meat, such as burgers and meatloaf, to reduce red meat consumption while maintaining flavor and texture.
Mushrooms are also increasingly used in supplement form due to growing interest in their antioxidant capacity. Indeed, thanks to increased evidence about the potential health benefits of mushrooms, interest in sustainable diets and even improved production and storage techniques, the global mushroom market is expected to nearly double, from $36.8 billion in 2016 to $69.3 billion, by the end of 2024.
What are the nutritional and health benefits of mushrooms?
Mushrooms contain up to 90% water, making them a low-calorie food high in micronutrients. They can be a good source of vitamin D if exposed to sunlight around the time of harvest, and they are a good source of most water-soluble B vitamins and minerals such as potassium, selenium and copper. They contain antioxidants such as flavonoids and carotenoids that help to prevent inflammation and various forms of cancer.
Mushrooms also include up to two grams per raw cup of both soluble and insoluble fiber. The stems are made of the soluble fiber called beta-glucans, which fuel our gut microbiota and control cholesterol. Mushrooms are among the few plant-based sources of conjugated linoleic acid, a type of omega-6 fatty acid that can help to improve various cardiometabolic risk factors, modulate immune function and impart other health benefits. L-ergothioneine is an amino acid found in mushrooms and is, in fact, only produced by fungi and mycobacteria. It accumulates in red blood cells and helps to protect them from oxidative damage.
On a population scale, people who consume more mushrooms have a lower risk of being overweight or obese and having metabolic syndrome. While these relationships are areas of active study, proposed mechanisms include providing a rich fiber source for gut bacteria and antioxidants that strengthen the immune system.
The cooking method may impact the nutritional value of mushrooms. A 2017 study by Roncero-Ramos et al. found that microwaving and grilling retained the most antioxidants while boiling and frying led to the greatest decline in antioxidants and protein. Drying mushrooms removes water, concentrates nutrients and extends shelf life. While some micronutrients may be lost during the process and prolonged storage, dried mushrooms may be more accessible for people unable to cook and consume fresh mushrooms on a regular basis.
The relatively recent attention to the medicinal benefits of mushrooms in the US has heightened interest in the consumption of unconventional forms of mushrooms, such as powders in coffee and hot chocolate. The powders and other unconventional forms may come from reishi, chaga, turkey tail, cordyceps or other specialty mushrooms.
Some human, animal and in vitro studies have shown evidence of health benefits from mushrooms in supplement form. While we typically want to focus on eating whole foods, many of these products may confer health benefits, such as stimulating healthy immune responses and protecting against cognitive impairment. Additionally, psilocybin mushrooms—also known as “magic mushrooms”—are known for their psychedelic effects. They have received increased interest in recent years and have been used in clinical trials in microdoses as an alternative treatment for headaches, anxiety and other mental health issues.
Tips for incorporating mushrooms into your diet:
Consider adding sautéed mushrooms to your favorite pasta, grain dish or salad.
Incorporate into dishes using ground red meat—such as hamburgers, meat loaf or taco filling—to boost the antioxidant and fiber content while reducing the meat content.
If you’re unable to keep and use fresh mushrooms, consider dried mushrooms that can be rehydrated and incorporated into recipes in place of fresh mushrooms.
When buying a processed mushroom food (such as jerky) or supplement (such as powder), consider whether it contains any fillers, preservatives or added sugar.
As a sweet treat with a nutritional boost, try making a mushroom hot chocolate.
To learn more about mushrooms, check out the film Fantastic Fungi, on demand now.
Beelman R. Ergothioneine in Mushrooms—Nature's Best Source of a New Human Vitamin? Presentation at Annual Mushroom Industry Conference. Pennsylvania State University. University Park, PA: 2006.
PDQ Integrative, Alternative, and Complementary Therapies Editorial Board. Medicinal Mushrooms (PDQ®): Health Professional Version. 2019 Oct 25. In: PDQ Cancer Information Summaries [Internet]. Bethesda (MD): National Cancer Institute (US); 2002.
Roncero-Ramos I, Mendiola-Lanao M, Pérez-Clavijo M, Delgado-Andrade C. Effect of Different Cooking Methods on Nutritional Value and Antioxidant Activity of Cultivated Mushrooms. Int J Food Sci Nutr. 2017;68(3):287-297.
Christina Badaracco, MPH, RD
Christina is a registered dietitian and author who aims to improve access to healthy and sustainable food and educate Americans about the connections between food and health. She loves to experiment with healthy recipes in the kitchen and share her creations to inspire others to cook.
Christina completed her dietetic internship at Massachusetts General Hospital and earned her Master of Public Health degree from the University of California, Berkeley. Previously, she graduated with a degree in Ecology and Evolutionary Biology from Princeton University, after conducting her thesis on sustainable agriculture and energy in Kenya. She has done clinical nutrition research at the National Institutes of Health, menu planning and nutrition education at the Oakland Unified School District and communications at the Environmental Protection Agency’s Office of Water. She has also enjoyed contributing to children’s gardens, farmers’ markets and a number of organic farms.