Wednesday, May 12, 2010

Bracken Fern--Cancer and Precaution

Everywhere I turned on the Internet, I found dire warnings. "Fiddleheads are great, but do not consume the bracken fern, a known carcinogen." But this warning was often extolled right alongside blatant misinformation like, "All other fiddleheads are edible." This last little tidbit was written by someone who I assume had never eaten interrupted fern fiddleheads. Personally, I'd warn someone against this foul-tasting, and seemingly toxic fern long before I ever talked them out of eating bracken. The Internet is awash in misinformation, gossip, and myths perpetuated by well-meaning but uncritical enthusiasts. So how does one find the truth? I don't want to use myself as a test case.

Here's another example: Sassafras is a sweet smelling tree of more southerly climes whose aromatic leaves can be brewed into a spicy tea, but many field guides contain a stern reprimand for those who over-indulge. It has been shown to cause cancer in laboratory rats. What a disappointment! It really was such a first-rate tea.

There are several key pieces of information missing from these overblown reports. First, just because something is carcinogenic or contains known carcinogens does not mean that it is unfit for human consumption. It is my understanding that we consume carcinogens all the time. We breath them in with the air. We eat them with our food. There are trace amounts in the water we drink. To be alive at all, no matter your species, is to be at risk of cancer.

Consider the story of the tropical plant, Coffea canephora, a member of the family Rubiaceae. It contains a mildly toxic alkaloid which acts to prolong the effects of certain hormones in the body, hormones like adrenaline. Many people consume a tea-like beverage made from the seeds of this plant--both to enjoy its flavor and to enjoy the "high" that accompanies the increase of active adrenaline in their system. In the 1980s it was found that consumption of this beverage correlates with an increase in pancreatic cancer. You can read about it in this abstract from the New England Journal of Medicine ( Yet millions of people continued to consume it every day. Perhaps you know of this plant. It's common name is coffee.

(There is an interesting twist in this story. As time went by, subsequent tests failed to confirm the correlation in the study on pancreatic cancer. Maybe coffee was benign after all. Science is the best tool we have for answering such questions, but science takes time and delivers its conclusions with varying degrees of certainty.)

Today, if you search the health news for coffee and cancer, you will find all kinds of claims. Coffee helps to prevent some kinds of cancer (prostate). It increases your chances of contracting others. Other cancers (colon) seem to be unaffected by coffee consumption. Does this conflicting advice ruin the day of most coffee drinkers? No. Coffee drinkers love coffee. Most of them would decide that a slight increase in contracting certain cancers might be worth a lifetime of enjoyment of their favorite beverage.

The question I ask about bracken fern and sassafras is not, "Is there a risk?" All eating, no matter what you choose to put in your mouth involves risk. The questions I ask are, "How great is that risk?" and, "Is it worth it?" The risks posed by most food plants are relatively low. Bracken fern is probably higher than most. This article reviews some of the research which demonstrates the link.

Even so, that risk may still be low enough to enjoy bracken as a regular part of one's diet.
Bracken fern contains a chemical, ptaquiloside, that is known to be carcinogenic to mammals in high doses. The International Agency for Research on Cancer places it in the same risk category as coffee and sassafras. This doesn't mean that if you eat bracken you'll die of cancer; many things that we commonly eat contain carcinogenic chemicals, such as char-broiled meat, potato chips, and all smoked foods. I still occasionally eat bracken fiddleheads. (Samuel Thayer retrieved from )
The rating Thayer is referring to is "Group 2B: Possibly carcinogenic to humans". The designation was made in 1987 and so does not include the findings of more recent research. A sampling of other things in Group 2B include: working as a carpenter, the food coloring Citrus Red #2, being around the fumes from automobiles and other engines, pickled vegetables, using talc-based body powder, and welding. Personally, I find the adventure of eating something new that I've gathered wild from forest worth taking a risk that is equivalent to drinking a cup of coffee or eating kimchi.


  1. Maybe one of the best things about foraging is that the FDA or other regulatory body won't be able to prevent you from trying something out. I mean plants like sassafras (which became unavailable commercially for a number of years). If you can find them and they aren't too rare to ehtically sample, then they're available at no cost but your time and effort.

    ps there is plenty of sassafras within your foraging radius.


  2. Excellent post, well done. Good info and advice.
    Regards, Le Loup.