GAINESVILLE, Fla. — Stroll the nutritional supplement aisle at your local drug store, and you might notice that some products are now featuring an ingredient you might expect to see growing on a tree or fallen log.

Known as the “mushroom of immortality” in traditional Eastern medicine, the reishi mushroom contains substances known for their anti-inflammatory and immune-boosting properties. In recent years, a multi-billion dollar industry of supplements and grow-your-own kits has marketed these fungi for their health benefits.

Generally, the dietary supplement industry is not regulated by the Food and Drug Administration (FDA), and products contain the following disclaimer: “This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.” The growing popularity of reishi products and lack of regulation from the federal government led one University of Florida doctoral student to wonder whether the labeling on these products was scientifically accurate.

That’s because “reishi” is a catch-all term for several different but related mushroom species. Historically, academia and industry have classified these mushrooms under the species Ganoderma lucidum.

“Over the years, there have been problems with distinguishing some species of Ganoderma from each other. Two different Ganoderma species might look superficially identical but are later discovered to be distinct at the genetic level,” said Andrew Loyd, who recently earned his doctorate in the UF/IFAS College of Agricultural and Life Sciences.

It’s still not known which Ganoderma species are most medicinally-relevant, though there is evidence that the amount and type of health-boosting substances differ from species to species, Loyd said. So, products that contain different Ganoderma species may have different medicinal properties, and when all of the products are labeled as including only one species (i.e. G. lucidum) the consumer is left with a buyer beware market

Ganoderma mushrooms aren’t the only fungi with a bit of mystery, Loyd said. There are many fungi species that scientists still aren’t sure how to classify—and some that haven’t even been discovered. “Only about 10 percent of fungi species on Earth are known. Compared with the 70 to 80 percent of plant and animal species scientists known about, fungi are a relatively new frontier,” Loyd explained.

As part of his doctoral research through the UF/IFAS School of Forest Resources and Conservation, Loyd led a study that analyzed Ganoderma DNA in 20 manufactured products, such as pills, tablets and teas, and 17 grow-your-own kits, which allow the consumer to grow the mushrooms themselves. Almost all of these products listed the species Ganoderma lucidum as a component.

Loyd and his co-investigators found that none of the manufactured products and only one of the kits actually contained Ganoderma lucidum. The most common substitution was the Asian species Ganoderma lingzhi, a species most often associated with traditional Chinese medicine. Tests also showed that a variety of other Ganoderma species were present. This included three species not native to the United States that American companies are selling as grow-your own kits to hobbyist and professional mushroom growers in the U.S. There is some concern with growing Ganoderma species outside of their native range escaping into the wild and displacing native decay fungi, potentially causing more aggressive decay on native trees. However, these implications are unknown at this point.

These findings suggest that some reishi products may not contain the mushroom species listed on the label. As Ganoderma species become better classified, this could allow for more accurate labeling of reishi products.

The study’s authors point out that better classification could aid in the discovery of new drugs derived from Ganoderma species, as well as establishing best management practices for growers regarding species selection.

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The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.

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