Warning Letter from the Food & Drug Administration | Are mushrooms medicinal?


Dear Mr.

This letter is to advise you that the U.S. Food and Drug Administration (F.D.A.) reviewed your website at https … in November 2020 and has determined that you take orders there for the products Cordyceps Militaris, Reishi, and … 

The claims on your website establish that the products are drugs under section 201(g)(1)(B) of the Federal Food, Drug, and Cosmetic Act (the FD&C Act) [21 U.S.C. 321(g)(1)(B)] because they are intended for use in the cure, mitigation, treatment, or prevention of disease.

The violations cited in this letter are not intended to be an all-inclusive statement of violations that exist in connection with your products. 

You are responsible for investigating and determining the causes of the violations identified above and for preventing their recurrence or the occurrence of other violations. 

It is your responsibility to ensure that your firm complies with all requirements of federal law, including F.D.A. regulations.

You should take prompt action to correct the violations cited in this letter. 

Failure to promptly correct these violations may result in legal action without further notice, including, without limitation, seizure and injunction.

Within fifteen (15) working days of receipt of this letter, please notify this office in writing of the specific steps you have taken to correct violations. 

Include an explanation of each step being taken to prevent the recurrence of violations, as well as copies of related documentation.


As I am not a U.S. citizen, this is a warning letter was not for me but for the owner of a U.S. mushroom company that sells different mushroom supplements to consumers.

What is happening here?

Why does the F.D.A. write this warning letter in the first place?

And are not mushrooms supposed to be medicinal?

Let us find out.

The history of mushrooms in medicine

The use of mushrooms in Traditional Chinese medicine or T.C.M. is a branch of traditional medicine and has a long history. Traces of therapeutic activities in China date from the Shang dynasty (14th to 11th centuries B.C.E.).

In T.C.M., health issues are seen as a manifestation of an imbalance within a patient. 

Treatments, therefore, are designed to restore balance. 

In contrast, western medicine addresses these issues by, for example, prescribing drugs. 

While the use of the fruitbodies of mushrooms like Reishi, Turkey Tail, Chaga, Maitake, or Cordyceps are sold as mushroom powders or extracts is common in T.C.M., they are not part of western medicine.

As the Chinese embrace modern medicine, the global appetite for herbal medicine has moved in the opposite direction leading to a worldwide market in 2019 of US$ 50 billion.

What does the scientific literature say about mushrooms?

To answer the question, today’s research paper investigated different mushrooms, their chemical compounds, and their use in medicinal settings.

To emphasize the statements made by the author, I will provide additional information given by one of the authors cited sources – the Memorial Sloan Kettering Cancer Center or short MSKCC.

The MSKCC is a cancer treatment and research institution in New York City founded in 1884 as the New York Cancer Hospital. 

It is the largest and oldest private cancer center globally. 

It is one of 51 National Cancer Institute-Designated Comprehensive Cancer Centers.

While I go briefly over each of the mushrooms you are likely to see a pattern.


The author writes that a handful of experiments on the properties of specific chemical compounds extracted from shiitake have been promising. 

The MSKCC concludes, “However, larger, well-designed studies are needed to establish the role of Lentinan as a useful adjunct to cancer treatment.”


The author wrote about Reishi that “the bracket fungus Ganoderma lucidum, called lingzhi (in China) and Reishi (in Japan), is one of the most popular medicinal mushrooms and has a history of use in China that is even older than the regional enthusiasm for shiitake.

The MSKCC concludes that more research is needed to determine its safety and effectiveness as an adjunctive cancer treatment.

Turkey Tail

The author concludes that the same conclusion can be made about the turkey tail.

The MSKCC states that “Coriolus Versicolor is a mushroom of the Basidiomycetes class. 

It is used in traditional Chinese medicine as a tonic. 

However, studies on breast cancer, hepatocellular carcinoma, and leukemia produced mixed results. 

Many over-the-counter Coriolus products are not standardized, making it difficult to compare potency between brands. 

It is also unclear if […] extracts have comparable effects.”


About the Chaga mushroom, the author writes, “Chaga, Inonotus obliquus, grows as a rock-hard excrescence from birch trees. 

The powdered sclerotia of Chaga have been used as a folk remedy against cancer, and the fungus is mentioned in Aleksandr Solzhenitsyn’s brilliant and disturbing novel ‘Cancer Ward’. 

Reviewing experiments showing the effects of Chaga extracts on cultured cells, the MSKCC […] concluded, ‘No clinical trials have been conducted to assess Chaga’s safety and efficacy for disease prevention or for the treatment of cancer, cardiovascular disease, or diabetes.”


Much the same applies to “Maitake, Grifola frondosa, also known as hen of the woods, a polypore that grows as masses of fruit bodies at the base of oak trees.”

As a first summary, the author of the paper writes: “The only thing that we can say with confidence is that extracts from shiitake, reishi, turkey tail, Chaga, and maitake stimulate cells in tissue culture experiments.”


About the cordyceps mushroom, the author wrote, “The ascomycete Ophiocordyceps Sinensis is another fungus associated with a range of pharmacological properties, including its effectiveness at reversing altitude sickness and erectile dysfunction.”

The MSKCC writes, “A few studies have also been conducted on humans […] [and] whether it exerts similar effects in humans is not known.”

Did you saw the pattern?

If not, you might just rewatch this part.

Claims made by companies

Companies which are selling all kinds of mushroom products making claims based on these studies even the results are inconclusive, stating, for example, 

  • Energy and endurance
  • Occasional stress adaptability
  • Athletic performance
  • Metabolic function
  • A blend of 17 potent mushroom species
  • The most comprehensive immune support formula
  • Encourages resistance to cellular assaults
  • Unique combination of mushroom mycelium and fruitbodies, providing a diverse range of constituents to help balance the immune system

Or publishing stories like 

Our founder and C.E.O., …, was continually zapped of energy. After trying everything, he eventually found functional mushrooms, specifically cordyceps militaris, which revived his energy and got him back on his feet. That is why he launched … to help people feel better and feel themselves. 

This kind of story is nothing more than anecdotal.

The regulators are entering the chat!

In the U.S., the Food, Drug, and Cosmetic Act (FD&C) give the U.S. Food and Drug Administration (F.D.A.) the authority to oversee the safety of food, drugs, medicinal devices, and cosmetics and have four responsibilities.

  1. […] protecting the public health […]
  2. […] regulating the manufacturing, marketing, and distribution […]
  3. […] advancing the public health […]
  4. […] plays a significant role in the nation’s counterterrorism capability […]

While the Food, Drug, and Cosmetic Act regulates mushroom products in the U.S.A., in the E.U., these products can fall under the Novel Food Regulation

This Regulation would define food as Novel Food if it were not consumed to a significant degree by humans in the E.U. before 15 May 1997, when the first Regulation on novel food came into force.

‘Novel Food’ can be newly developed, innovative food, food produced using new technologies and production processes, as well as food which is or has been traditionally eaten outside of the E.U.

The underlying principles underpinning Novel Food in the European Union are that Novel Foods must be:

  • Safe for consumers.
  • Properly labeled so as not to mislead consumers.
  • If novel food is intended to replace another food, it must not differ in a way that the consumption of the Novel Food would be nutritionally disadvantageous for the consumer.

Under this Regulation, each food is classified into one of the following four categories.

· No Novel Food

· No Novel Food, but other food uses of this product have the be authorized.

· Request to require authorization. The product falls under the Novel Food Regulation.

· Request to require authorization. Further information is required.

In addition to this Regulation, Health Claims, which are any statement about a relationship between food and health, must be authorized. 

The consequences of not following the rules

Let us continue with the warning letters from the F.D.A. In the warning letters the F.D.A. stated that after reviewing the websites, they conclude that the claims made on the websites establish that these products are drugs under section 201(g)(1)(B).

The letter then contains examples of the claims made on these websites. 

Followed by the statement that the products are not generally recognized as safe and effective for the above-referenced uses and, therefore, these products are “new drugs” under section 201(p) of the FD&C Act.

Stating further that new drugs may not be legally introduced or delivered for introduction into interstate commerce without prior approval from the F.D.A.

The letters are finishing off with the notice that “you should take prompt action to correct the violation cited in this letter. 

Failure to promptly correct these violations may result in legal action without further notice, including, without limitation, seizure, and injunction.” 

Or to be more precise.

Violations of the Act, and if found guilty, will be subject to the penalties specified by the law.

To enforce the Act, the F.D.A. uses the following actions.

· Warning letters which I am talking about

· seizure

· injunction

· Criminal prosecution

Misdemeanor fines under the Act can reach $500,000 under some circumstances.

How to avoid punishment*

As a consequence of this warning letter, the company placed the following disclaimer next to their products. 

“These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.” 

Variations of this disclaimer on other websites are 

“Please consult your physician before using any of our products for health purposes. *These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.”


“The statements made on this website have not been evaluated by the F.D.A. (U.S. Food & Drug Administration). The products sold on this website are not intended to diagnose, treat, cure, or prevent any disease. The information provided by this website or this company is not a substitute for a face-to-face consultation with your physician and should not be construed as individual medical advice.”

The author of today’s research paper further compared the offering of these products on the one side and placing a disclaimer next to them with “making bicycles and telling customers that they are not meant to be ridden!”

I think it is more like making bicycles and telling customers that the regulators did not validate the claim made that you could ride the bike!


Going again back to the article, the author made it clear that pursuing this critical exploration of medicinal mushrooms is important as it seems very likely that mushrooms do contain compounds with important pharmacological properties.

He writes, “This optimism is encouraged by the deep history of interactions between fruit bodies and potentially fungivorous animals. 

The ability of fruit bodies to survive damage by insects and other pests long enough to release spores suggests that they generate a range of cryptic antifeedants that interact with molecular targets in animals.”

He continuous: “Disregarding the dafter ideas about medicinal mushrooms, it is possible that these fungi offer a treasure trove of uncharacterized metabolites that could prove useful in treating our illnesses.”

And further: “Putting aside the current fantasies about mushrooms, there are good reasons for surveying the galaxy of metabolites in these organisms.” 

After all, other kinds of fungi are the source of antibiotics old (penicillin) and new (cephalosporins), the cholesterol-lowering drug lovastatin, and cyclosporins for supporting patients after organ transplants. 

Miraculous drugs may be sitting in the least prepossessing fruit bodies. 

And with a choice of 16 000 or more species of basidiomycetes that form mushrooms, there are lots of places to look” and, therefore, “proceed with the exploration of novel compounds with the potential to change the course of our modern plagues.”

Talk to you in the next video.


[1] https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/compliance-actions-and-activities/warning-letters

[2] 📝Nicholas P. Money, Are mushrooms medicinal?, Fungal Biology, Volume 120, Issue 4, 2016, Pages 449-453, ISSN 1878-6146, https://doi.org/10.1016/j.funbio.2016.01.006.

[3] https://ec.europa.eu/food/safety/novel-food_en and https://ec.europa.eu/food/safety/novel_food/catalogue/search/public/index.cfm


The content of this website is for educational and informational purposes only. It is not intended to give you legal advice nor medicinal advice. Please contact a professional to obtain advice with respect to any particular issue or problem.