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Coffee, Beyond Caffeine

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Coffee—caffeinated or decaffeinated—protects liver and gastrointestinal cells from toxic compounds, according to Sandra Kalthoff et al. in the November issue of Gastroenterology.

In many epidemiology studies, coffee consumption reduced the risk of inflammation, chronic liver diseases, hepatocellular carcinoma (HCC), and other GI disorders. Its mechanisms are unclear, however, because coffee contains many complex compounds. Studies have shown that caffeine increases intracellular cAMP levels and disrupts TGF-ß signaling, whereas the coffee oils cafestol and kahweaol inhibit binding of aflatoxin B to DNA, induce glutathione-S-transferase, and protect against genotoxicity.

Kalthoff et al. add to the list of coffee’s super-powers, reporting that coffee increases production of UDP-glucuronosyltransferases (UGT1A )—enzymes with antioxidant, cytoprotective and genoprotective effects that mediate detoxification in the liver.

The authors discovered this effect after incubating liver, colon, and esophageal cells with different types of coffee (metal- and paper-filtered, boiled, decaffeinated, and instant) and related drinks (green and black tea and cocoa); paper-filtered coffee contains less cafestol and kahweaol, decaffeinated coffee lacks caffeine, and tea contains caffeine but is not processed by roasting. All preparations, except for black tea, induced transcription of the family of UGT1A genes, which encode enzymes that catalyze the formation of glucuronides from carcinogens and reactive oxygen species. These effects also occurred in vivo—giving coffee to mice upregulated UGT1A 10-fold or more in liver and stomach. 

UGT1A induction was independent of caffeine, methylxanthines, cafestol, or kahweaol, so more studies are needed to find out what compound or combination of compounds are required to induce transcription. Nonetheless, Kalthoff et al. propose that coffee extracts might be used as chemoprotectants against HCC, chronic hepatitis, or other liver diseases in high-risk groups. 

Antioxidant capacity of tested beverages.

Read the article online:
Kalthoff  S, Ehmer U, Freibert N, et al.  Coffee induces expression of glucuronosyltransferases by the aryl hydrocarbon receptor and Nrf2 in liver and stomach. Gastroenterology 2010;139:1699–1710.e2.

Read the accompanying editorial:
Gressner OA.  In the search of the magic bullet…Gastroenterology 2010;139:1453–1457.

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About The Author:

Dr. Kristine Novak

Dr. Kristine Novak

Dr. Kristine Novak is a science writer and editor based in San Francisco. She has extensive experience covering gastroenterology, hepatology, immunology, oncology, clinical, and biotechnology research discoveries.

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