Wise Mind Herbs

The information on this page has been prepared with reference to published scientific literature, not by a medically qualified expert. It is not medical advice. Any decision to use a supplement or herb-based product is your responsibility. Consult a suitably qualified medical professional, especially if you have underlying conditions. Remember, nothing is for everyone, and not everything sold is what it claims to be. Some things work for some people, some of the time.

Bracken (Pteridium aquilinium)

I must begin this review with an important caution: Bracken fern (Pteridium aquilinum) is not recognized as a medicinal plant in contemporary evidence-based medicine. On the contrary, it is well-established in scientific literature as a toxic plant that poses significant health risks when consumed. This review will clarify the scientific evidence regarding bracken, its compounds, and health implications.

Image source and license:https://commons.wikimedia.org/wiki/File:Fern_dsc06699.jpg.
Modified by Peter Jorgensen.

Botanical Identity and Common Names

Pteridium aquilinum, commonly known as bracken, bracken fern, or eagle fern, is one of the most widely distributed fern species globally. It belongs to the Dennstaedtiaceae family. Other common names include brake fern, pasture brake, and western brackenfern. Species within the Pteridium genus that may be confused with P. aquilinum include P. esculentum (Australian bracken) and P. revolutum, though they share similar toxic properties.

Plants sometimes confused with bracken but belonging to different genera include Matteuccia struthiopteris (ostrich fern, which produces edible fiddleheads) and various Athyrium species (lady ferns). These distinctions are critical as these other ferns do not share bracken's extreme toxicity profile.

Bioactive Compounds in Bracken

Bracken contains several bioactive compounds, with the most significant being:

• Ptaquiloside - a norsesquiterpene glycoside and the primary carcinogenic compound
• Cyanogenic glycosides - which can release hydrogen cyanide
• Thiaminase - an enzyme that breaks down thiamine (vitamin B1)
• Various tannins and phenolic compounds
• Prunasin and other glycosides

Purported Traditional Uses

While bracken has been used in some traditional medicine systems historically, particularly in parts of Asia and among certain indigenous communities, these uses are not supported by modern scientific evidence and are considered dangerous based on current knowledge. Historical applications included treatments for intestinal worms, respiratory ailments, and wound healing, but these uses predated understanding of bracken's carcinogenicity.

Evidence-Based Health Effects

Contrary to providing health benefits, scientific research has consistently demonstrated significant health risks associated with bracken consumption:

• Carcinogenicity - Ptaquiloside and related compounds are established carcinogens that cause DNA damage and chromosomal aberrations
• Thiamine deficiency - The thiaminase enzyme destroys vitamin B1, potentially leading to neurological disorders
• Bone marrow suppression - Bracken consumption has been linked to aplastic anemia and other hematological disorders
• Bladder and intestinal hemorrhage - Particularly observed in livestock consuming bracken
• Harmful compounds can bioaccumulate in mammary glands, and be excreted via milk

Clinical Studies and Efficacy

There are no legitimate clinical trials investigating bracken as a therapeutic agent. Research has instead focused on understanding its toxicology and carcinogenic mechanisms. Multiple epidemiological studies have linked bracken consumption with increased rates of esophageal and gastric cancers in humans, particularly in Japan, Brazil, and Wales where bracken has historically been consumed as food.

Dosage and Safety Information

No safe dosage of bracken exists for human consumption. Health authorities worldwide, including the FDA, EFSA, and WHO, recognize bracken as a toxic plant unsuitable for human consumption at any level. The ptaquiloside content varies significantly (0.02-1.3% dry weight) depending on geographic location, season, plant part, and growth stage, making any attempted standardization for medicinal purposes both dangerous and impractical.

Known Side Effects and Toxicity

Acute toxicity from bracken consumption may include:

• Gastrointestinal distress including vomiting and diarrhea
• Neurological symptoms from thiamine deficiency
• Hematological abnormalities including reduced platelet and white blood cell counts

Chronic toxicity, which is of greater concern, includes:

• Significantly increased risk of various cancers, particularly of the digestive tract, bladder, and hematopoietic system
• Progressive bone marrow suppression
• Immunosuppression
• Chronic neurological damage

Research on High-Dose Exposure

Multiple toxicological studies have examined high-dose bracken exposure in animal models. These consistently demonstrate dose-dependent increases in carcinogenicity and other toxic effects, with no evidence of hormetic or beneficial effects at any dosage. The research conclusively indicates that higher doses accelerate and intensify toxic outcomes rather than producing therapeutic benefits.

Knowledge Gaps

While bracken toxicity is well-established, some research gaps remain:

• Complete characterization of all bioactive compounds and their interactions
• Precise mechanisms of genotoxicity for some bracken compounds beyond ptaquiloside
• Comprehensive understanding of geographic and environmental factors influencing toxin concentration
• Long-term epidemiological studies on low-level environmental exposure through contaminated water or milk

Commercial Pharmaceutical Products

There are no legitimate pharmaceutical products derived from bracken or its compounds. Any products marketed as medicinal bracken preparations should be regarded with extreme caution given the overwhelming scientific evidence of toxicity. Responsible pharmaceutical companies avoid bracken-derived compounds due to their established carcinogenicity.

Research into bracken has primarily focused on developing methods to detect ptaquiloside contamination in food, water, and dairy products rather than medicinal applications.

Conclusion

The scientific literature provides robust evidence that bracken (Pteridium aquilinum) is a toxic and carcinogenic plant unsuitable for medicinal use. Despite some historical traditional applications, contemporary research has thoroughly documented its harmful effects. Health authorities universally advise against human consumption of bracken in any form. As it can be passed on through meat and dairy products, cattle intended for human consumption should never be permitted to graze on bracken; this could lead to products like milk and beef becoming highly carcinogenic. Any potential for medicinal development would require isolation, modification, and extensive safety testing of specific compounds to eliminate the significant risks that the natural plant material presents.

References

Aranha, P. C. D. R., Rasmussen, L. H., Wolf-Jäckel, G. A., Jensen, H. M. E., Hansen, H. C. B., & Friis, C. (2019). Fate of ptaquiloside—A bracken fern toxin—In cattle. PLoS One, 14(6), e0218628.

Da Costa, R. G., Bastos, M. M., Oliveira, P. A., & Lopes, C. (2012). Bracken-associated human and animal health hazards: Chemical, biological and pathological evidence. Journal of hazardous materials, 203, 1-12.

Latorre, A. O., Caniceiro, B. D., Fukumasu, H., Gardner, D. R., Lopes, F. M., Wysochi Jr, H. L., ... & Górniak, S. L. (2013). Ptaquiloside reduces NK cell activities by enhancing metallothionein expression, which is prevented by selenium. Toxicology, 304, 100-108.

Lee, H. H., Kim, A. G., Lee, M. G., Choi, S. Y., Seo, J. J., Kim, E. S., ... & Cho, B. S. (2017). Study on Processing Methods to Remove Toxic Ptaquiloside from Bracken Fern. Journal of Food Hygiene and Safety, 32(3), 217-221.

Malík, M., Mika, O. J., Navrátilová, Z., Killi, U. K., Tlustoš, P., & Patočka, J. (2023). Health and Environmental Hazards of the Toxic Pteridium aquilinum (L.) Kuhn (Bracken Fern). Plants, 13(1), 18.