Inside plants

Image Gallery G. Ford

WHICH ITEM is the misfit in this group: a man, a milk thistle, or a mushroom?

Okay, it’s a trick question. In terms of scientific classification, mushrooms are as different from flowering plants as humans are. In fact, fungi aren’t even part of the Plant Kingdom—they have a kingdom all their own.

Fungi are primitive compared with flowering plants, which make up the overwhelming majority of the world’s culinary and medicinal herbs. Flowering plants use photosynthesis to convert sunlight and carbon dioxide into their primary food, a sugar called glucose. Glucose is also the primary food for animals, including humans, and comes from our food. When we talk about blood sugar, we mean glucose.

In comparison, fungi “steal” glucose from plants and animals. Fungi are either saprophytes, which obtain nutrients by digesting dead organisms, or parasites, which feed off the living. Mushrooms growing on a dead log come to mind—these fungi are taking advantage of years of work done by the tree to store energy in its trunk.

Fungi aren’t primitive when it comes to manufacturing phytochemicals, however, which makes the distinction between fungi and true plants nearly invisible to the chef or herbalist. Some fungi produce phytochemicals that create delicious aromas and tastes, making mushrooms such as morels, truffles, and corn smut prized culinary ingredients. Other mushrooms have ghastly stenches or are hallucinogenic or poison­ous. In between lies a group of medicinal mushrooms that may or may not be tasty, but possibly provide health benefits. Of 10,000 species of mushrooms, about 700 are considered edible and less than 200 are considered medicinal.

The mushrooms shiitake (Lentinula edodes), reishi (Ganoderma lucidum), maitake (Grifola frondosa), and hoelen (Poria cocos) are used in traditional Asian medicine to stimulate the immune system and treat chronic wasting diseases such as cancer, tuberculosis, hepatitis, and AIDS.

Common to all these mushrooms are phytochemicals called glycans, proteoglycans, beta-glucans, and polysaccharides. In a nutshell, these compounds are forms of glucose, that all-important energy source. In nature, glucose molecules link together to form polymers, chemical compounds built like chains or netting of repeating structural units such as sugars. The term polysaccharide means just that—many ­sugars.

Glucose molecules linked together in one way create digestible starches such as potatoes or rice. Glucose linked together in a different way is not digestible, but makes for healthy dietary fiber. The glucose most important to mushrooms comes in long chains and forms the cellulose in a tree trunk.