Fungi, Food, and Toxins

Ingesting fungi (mycophagy) is a common and often pleasant experience. In some cases, one eats them by choice, as with gourmet mushrooms, and quite frequently, they are unintentionally consumed in dairy products such as yogurt and cottage cheese, fruits, vegetables, and many other foods. Although most of the fungi we eat accidently are harmless, poisonous ones cause toxic illness.

A number of mushrooms and molds contain mycotoxins that act on the central nervous system, liver, gastrointestinal tract, bone marrow, or kidney. The primary cause of mycotoxicosis is the consumption of wild mushrooms, a centuries-old practice that has taken the life of many an avid mushroom hunter. 

The deadliest of all mushrooms is Amanita phalloides, the so-called death-angel or destroying angel, whose cap contains enough toxin to kill an adult, though this happens rarely. Clearly, collecting and eating wild mush- rooms is recommended only for the most expert mycophagist, and the rest of us should be content to gather mushrooms in the grocery store. Certain poisonous fungi have been signifcant in history, and others are tied to ancient religious practices. Rye plants infested by Claviceps purpurea develop black masses, known as ergot, on the grains. When such rye grains are inadvertently incorporated into food and ingested, absorption of the ergot alkaloids causes ergotism. People thus intoxicated exhibit convulsions, delusions, a burning sensation in the hands, and symptoms similar to LSD (lysergic acid diethylamide) poisoning. This latter symptom occurs because the alkaloids in Claviceps and other mind-altering fungi contain the active ingredient lysergic acid. In the Middle Ages, millions of people died from ergotism, but now the disease is very rare. Mycotoxicosis is also caused by food contaminated by fungal toxins. 

One of the most potent of these toxins is aflatoxin, a product of Aspergillus flavus growing on grains, corn, and peanuts. Although the mold itself is relatively innocuous, the toxin is carcinogenic and hepatotoxic. It is especially lethal to turkeys, ducklings, pigs, and calves that have eaten contaminated feed. In humans, it appears to be a cofactor in liver cancer. The potential hazard aflatoxin poses for domesticated animals and humans necessitates constant monitoring of peanuts, beer, grains, nuts, vegetable oils, animal feed, and even milk. Aquick exposure of seeds to ultraviolet radiation is a useful screening test because they glow when contaminated by the toxin.

Toxic fungi are a growing source of environmental acquired illnesses associated with contaminated buildings. Stachybotrys spores and toxins inhaled from air are a known cause of serious neurologic disease. Other airborne fungi cause asthma and related respiratory allergies.