Chicory's defensive compounds make a tasty hot drink

By Jeff Mitton

Chicory caught my eye when I was a young boy, for it has axillary rather than terminal flowers.

Terminal flowers are at the end of a stem, while axillary flowers are at the junction of a stem and the base of a leaf.

This year I noted that pollinators of all sorts attend its pretty blue flowers, but I have never seen any sucking or chewing insects on chicory, nor have I seen chewing damage to its leaves.

Chicory's charms were discovered shortly after 1766, when Frederick the Great banned the importation of coffee into Prussia. An innkeeper in Brunswick found that the root of chicory, when dried, ground and roasted, made a bitter but tasty substitute for coffee.Chicory, Cichorium intybus, is a composite (in the sunflower family) native to France and Italy, but introduced to and widely naturalized in North America, Australia and New Zealand.

Naturalized means that it has moved from weedy sites such as roadsides into pastures, meadows and forests. Numerous plant species have moved about the world by accident, but chicory's introduction was not accidental. It was purposely introduced because it has benefits for both man and beast.

Chicory's charms were discovered shortly after 1766, when Frederick the Great banned the importation of coffee into Prussia. An innkeeper in Brunswick found that the root of chicory, when dried, ground and roasted, made a bitter but tasty substitute for coffee.

Its popularity spread, and today chicory is cultivated in Germany, France and Belgium.

Coffee was the most popular hot drink in the U.S. until the Civil War started, and the Union Army blockaded New Orleans, one of the major ports importing coffee. Without coffee, the Confederate Army adopted chicory. New Orleans never lost its taste for chicory — it is still available at many cafes and restaurants in the city.

Here in Boulder, chicory is available in at least one of the restaurants, chicory tea is made and sold, and several breweries use chicory in their stouts.

The leaves of chicory can be eaten raw, as one of several greens in a salad. But some people find the leaves to be too bitter. Blanching of leaves reduces their bitterness.

The same molecules provide chicory's bitter taste and its freedom from insect herbivory.

Laboratory experiments with locusts have demonstrated that three sequiterpene lactones (lactucin, lactupicrin, 8-deoxylactucin) and a phenolic (cichoriin) act as feeding deterrents for locusts.

Similar studies, with a diversity of insects, discovered that few species of insects could survive if they are restricted to eating chicory foliage. The three sequiterpene lactones are suspended in latex, which is generally recognized as a general plant defense and known for its ability to clog and gum up the mouthparts of small insects.

The molecules that make chicory distasteful for insects make chicory appealing to humans with adventurous tastes.

It is generally acknowledged that chicory influences the intestinal environment, and farmers have introduced it to pastures used to feed horses, cows, goats and sheep.

Careful studies of chicory's influence on parasites have reported that the number of intestinal worm eggs detected in feces is lower in sheep fed in pastures containing chicory. However, the results can be conflicting.

For example, a study, which reported that the number of worm eggs declined by 64 percent in the feces of piglets fed chicory, but also reported that the number of worms in those same animals had increased. Chicory is purposefully introduced into pastures in Australia and New Zealand.

Chicory metabolizes a variety of defensive compounds and is now generally free of insect herbivores. Many ranchers and farmers believe that chicory reduces intestinal worms of horses, cows, goats and sheep. Its use as a coffee substitute fluctuates through time, but increases sharply when political events limit the availability of coffee or dramatically increases its cost.

I find it fascinating that compounds that evolve to discourage insect herbivores have caused ranchers, farmers and beverage lovers to move chicory from continental Europe throughout the world.

Jeff Mitton, mitton@colorado.edu, is a professor in the Department of Ecology and Evolutionary Biology at the University of Colorado. This column originally appeared in the Boulder Daily Camera.

Nov. 20, 2014