Bitter Coffee, Better Health?

Reading time: 4 – 6 minutes

I love my coffee. Who doesn’t want (or need for all you coffee addicts out there) a cup of freshly brewed java to start their day? However, the bitterness of coffee is something most of us could do without.

Now chemists in Germany and the U.S. say they have identified the chemicals that are largely responsible for coffee’s bitterness. Their study, one of the most detailed chemical analyses of coffee bitterness to date, was presented this week at the 234th national meeting of the American Chemical Society [1].

coffee+apple.jpgContrary to popular belief, only 15% of coffee’s perceived bitterness is due to caffeine [1]. In fact, coffee is a complex mixture of chemicals and an estimated 25 to 30 compounds have been thought to contribute to coffee’s bitter taste. Surprisingly, however, the chemists found that coffee’s bitterness is due to two main classes of compounds produced during the roasting process; chlorogenic acid lactones and phenylindanes. Both compounds are antioxidants and are not present in green, unroasted coffee beans.

During roasting, chlorogenic acid, a polyphenol in raw beans, is converted to chlorogenic acid lactones. Further roasting results in the breakdown of the lactones to phenylindanes. The lactones are responsible for the mild bitterness of light- to medium-roasted coffee, while the second breakdown product, phenylindanes, produce the harsh, bitter taste of dark-roasted coffee.

Chlorogenic acid lactones have been known for some time to be produced by the roasting process [2], but their role as a source of bitterness was not known until now. Perhaps more importantly, the identification of phenylindanes adds to the growing body of knowledge investigating the health benefits of coffee.

What you say? Health benefits?

Indeed, coffee consumption offers a number of potential health benefits. The results of epidemiological research suggest that moderate coffee consumption may help prevent type 2 diabetes mellitus [3-4], Parkinson’s disease [5] and liver disease [6]. Although coffee consumption has not been found to be associated with significantly increased cardiovascular disease risk, it is associated with increases in several cardiovascular disease risk factors, namely blood pressure [7] and plasma homocysteine [8]. Some individuals may be more vulnerable to the adverse effects of caffeine in coffee, including people with hypertension, children, adolescents and the elderly. Nevertheless, habitual intake of caffeinated beverages may prevent heart disease in the elderly.

It’s been suggested that this research on coffee bitterness will lead to a “better cup of joe”. However, I wouldn’t be too surprised if the the compounds that give coffee its bitter taste also turn out to be responsible for coffee’s health benefits.


  1. Battling Bitter Coffee: Chemists Identify Roasting As The Main Culprit. ScienceDaily 2007 Aug 22.
  2. Farah et al. Effect of roasting on the formation of chlorogenic acid lactones in coffee. J Agric Food Chem. 2005 Mar 9;53(5):1505-13.
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  3. Salazar-Martinez et al. Coffee consumption and risk for type 2 diabetes mellitus. Ann Intern Med. 2004 Jan 6;140(1):1-8.
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  4. van Dam and Hu. Coffee consumption and risk of type 2 diabetes: a systematic review. JAMA. 2005 Jul 6;294(1):97-104.
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  5. Ascherio et al. Prospective study of caffeine consumption and risk of Parkinson’s disease in men and women. Ann Neurol. 2001 Jul;50(1):56-63.
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  6. Ruhl and Everhart. Coffee and tea consumption are associated with a lower incidence of chronic liver disease in the United States. Gastroenterology. 2005 Dec;129(6):1928-36.
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  7. Noordzij et al. Blood pressure response to chronic intake of coffee and caffeine: a meta-analysis of randomized controlled trials. J Hypertens. 2005 May;23(5):921-8.
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  8. Olthof et al. Consumption of high doses of chlorogenic acid, present in coffee, or of black tea increases plasma total homocysteine concentrations in humans. Am J Clin Nutr. 2001 Mar;73(3):532-8.
    View abstract
About the Author

Walter Jessen, Ph.D. is a Data Scientist, Digital Biologist, and Knowledge Engineer. His primary focus is to build and support expert systems, including AI (artificial intelligence) and user-generated platforms, and to identify and develop methods to capture, organize, integrate, and make accessible company knowledge. His research interests include disease biology modeling and biomarker identification. He is also a Principal at Highlight Health Media, which publishes Highlight HEALTH, and lead writer at Highlight HEALTH.