Ah, the dichotomy of mycophagy. That statement sounded pretty darn impressive, didn't it? Admit it, you were a little impressed. Morels, truffles, and king boletes are arguably among the most saporous and sought-after foods out there, while false morels, Amanitas (which include the aptly-named Death cap and Destroying angel), and the Lethal webcaps will generally kill you if you eat them.
Then there's the genus Agaricus. It includes a number of species known to be at least mildly poisonous, as well as several others that are consumed around the world on a daily basis. The common store mushroom, Agaricus bisporus, also known as the commercial mushroom and the button mushroom, is by far the most popular of these, with hundreds of millions of the little guys being produced and consumed annually. The cream-coloured bundle of succulence (yeah, you read that right) that is sold today is actually a mutant strain discovered in Pennsylvania in 1926. The original cultivated strain was a light brown, but at the time white was very trendy. Another familiar strain of A. bisporus is the Portobello mushroom, which has retained the brown colour but is much larger with a thick cap and stem, enabling it to be strangely consumed in burger form.
Other wild species of Agaricus that people eat include A. campestris (the field mushroom), A. arvensis (the horse mushroom), and A. augustus (called the "prince", although I suspect the "emperor" might fit better). These are good eating, but don't go hunting for 'em unless you're an expert. And by that I mean a trained mycologist, not some dude who read a book and "hasn't got sick yet".
All species of Agaricus contain hydrazines, which are compounds that contain two bonded nitrogen atoms. Of these, which include in their ranks such luminaries as gyromitrin and monomethylhydrazine, the most abundant is an aromatic hydrazine known as agaritine.
The vast majority of hydrazines are known carcinogens. Agaritine is rapidly broken down by animal enzymes to form 4-(hydroxymethyl)phenylhydrazine (HMPH) and 4-(hydroxymethyl)benzenediazonium ions (HMBD), both of which are very unstable and have been shown to be carcinogenic. Extracts of A. bisporus have been shown to damage DNA in test tubes (Ames test) and it has been demonstrated that mice display a significant increase in the incidence of several types of tumours after they are fed uncooked mushrooms. As there is currently insufficient evidence to conclude otherwise, agaritine is presently only suspected to cause cancer in humans.
It should be noted that agaritine and its derivatives are likely degraded by heat, so cooking your mushrooms would be expected to lower the risk of developing cancer. If such a risk is real. But honestly, raw mushrooms can't compete with ones that have been sauteed in butter.
- Kondo K, Watanabe A, Akiyama H, Maitani T. The metabolisms of agaritine, a mushroom hydrazine in mice. Food Chem Toxicol. 2008 Mar;46(3):854-62. Epub 2007 Dec 3.