Caffeine itself has a particularly bitter taste.  Surprisingly, a new study at Northwestern University has found that the more sensitive people are to the bitter taste of caffeine, the more coffee they drink. That sensitivity is actually a genetic variant.

So, one would think that people who are especially sensitive to the bitter taste of caffeine would drink less coffee.  The counter intuitive result suggests that coffee consumers acquire a taste or an ability to detect caffeine as a result of the learned positive reinforcement (in other words, the buzz) elicited by caffeine.  People with a heightened ability to taste coffee’s bitterness learn to associate good things with it.

The study also found in contrast that people sensitive to the bitter flavor of a different compound called 6-n-propylthiouracil (known as PROP)avoided coffee as well as red wine.

The study made use of applied Mendelian randomization, a technique commonly used in disease epidemiology, to test the causal relationship between bitter taste and beverage consumption in more than 400,000 men and women in the United Kingdom.

These results shed some light on the disdain many coffee drinkers have for decaf coffee.  It may not be just the lack of buzz that turns them off.  Some of them with the right genes may be missing that extra bit of bitterness that alerts them that something good is about to happen.

**********

Why we shouldn’t like coffee, but we do

Photo, posted May 22, 2009, courtesy of Olle Svensson via Flickr.  

Earth Wise is a production of WAMC Northeast Public Radio.