If you enjoy coffee, you appreciate its acidic flavor. Chlorogenic acids are the most abundant of the many naturally occurring acids in green and roasted coffee beans; others include quinic, lactic, malic, citric, lactic and acetic acid. Although other plants also contain chlorogenic acids, coffee beans contain a higher concentration than most food sources. In addition to contributing flavor to coffee, chlorogenic acids may affect some of your body tissues.
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Chlorogenic acids, or CGAs, include a group of closely related chemicals that possess a similar molecular structure. The most abundant chlorogenic acid in coffee is 5-caffeoylquinic acid. Your body metabolizes chlorogenic acid into its component chemicals, quinic acid and caffeic acid. Other CGAs in coffee include dicaffeoylquinic, feruloylquinic and coumaroylquinic acid. The relative concentrations of the various CGAs in coffee beans affect the flavor and aroma of coffee.
The concentration of the various chlorogenic acids in coffee varies, depending on the type of coffee beans, roasting, grinding and preparation. Robusta coffee beans typically contain higher levels of CGAs than Arabica beans, which partially accounts for the difference in flavor between these two varieties of coffee beans. CGA levels in coffee beans decrease during roasting. Therefore, dark-roasted coffee contains a lower concentration of CGAs than light roasts. Finely ground coffee beans yield higher concentrations of CGAs than coarsely ground beans. The level of CGAs in coffee also tends to increase with its brewing temperature. A 7 oz. cup of coffee contains approximately 70 mg to 350 mg of chlorogenic acids, reports food scientist Jane Higdon, Ph.D., in the text "An Evidence-based Approach to Dietary Phytochemicals."
Potential Antioxidant Effects
In laboratory experiments, chlorogenic acids demonstrate potent antioxidant effects, meaning they neutralize chemicals that can potentially damage your body tissues. Because CGAs rapidly break down in your body, however, biomedical scientists remain uncertain about the extent to which the antioxidant effects seen in the laboratory might affect human health. Despite a tremendous amount of media attention, evidence to support the role of antioxidants in chronic disease prevention remains weak.
Potential Protection Against Diabetic Cataracts
Diabetics have an increased risk for cataracts, or clouding of the lens of the eye. This condition can eventually lead to significant vision loss or blindness. In a March 2001 article in the "Biological & Pharmaceutical Bulletin," Dr. Young Sook Kim and colleagues report that CGAs helped to prevent the development of diabetic cataracts in an animal model study. Additional research is needed to determine whether this promising laboratory research can be translated into a beneficial prevention strategy for people living with diabetes.
- CoffeeResearch.org: Coffee Chemistry: Coffee Acidity
- "An Evidence-based Approach to Dietary Phytochemicals"; Jane Higdon, Ph.D.; 2007
- "Phenolics in Food and Nutraceuticals"; Fereidoon Shahidi, Ph.D., et al.; 2004
- CoffeeChemistry.com: Chlorogenic Acid
- Harvard School of Public Health: Antioxidants: Beyond the Hype