Green Tea Health Benefits Blog

Is Caffeine in Green Tea All Bad?

August 8th, 2005

We get two types of questions related to green tea and caffeine one set wonders if the presence of caffeine reduces green tea’s healthful effects. the other set of questions take the opposite approach. Some people wonder if the process of decaffeination reduces green tea’s health benefits. The greentealover’s site explains in great detail:

• Comparisons between the amount of caffeine in green tea and other beverages like coffee (in green tea its lower)
• How the amino acid Theanine counteracts some of the effects of caffeine in green tea
• What you can do to naturally decaffeinate your green tea
• What type of decaffeination process you should always look for when buying tea (there are two - one uses natural processes the other chemical solvents.

This blog post deals with a couple of studies that point to caffeine providing some health benefit in green tea:

The Department of Chemical Biology, College of Pharmacy, at Rutgers studied the effects of tea, decaffeinated tea, and caffeine on UVB light-induced complete carcinogenesis in SKH-1 mice: demonstration of caffeine as a biologically important constituent of tea(1). They found oral administration of green or black tea inhibited UVB light-induced complete carcinogenesis in the skin of SKH-1 mice(1). Green tea was a more effective inhibitor than black tea. Oral administration of decaffeinated green or black tea resulted in substantially less inhibitory activity than did administration of the regular teas, and in one experiment, administration of a high-dose level of the decaffeinated teas enhanced the tumorigenic effect of UVB. Oral administration of caffeine alone had a substantial inhibitory effect on UVB-induced carcinogenesis, and adding caffeine to the decaffeinated teas restored the inhibitory effects of these teas on UVB-induced carcinogenesis. In additional studies, topical application of a green tea polyphenol fraction after each UVB application inhibited UVB-induced tumorigenesis. The results indicate that caffeine contributes in an important way to the inhibitory effects of green and black tea on UVB-induced complete carcinogenesis.

The Department of Nutritional Science and Dietetics, University of Nebraska did another study on Green and black tea consumption by humans: impact on polyphenol concentrations in feces, blood and urine. The objective of the study was to determine the effects of green tea, black tea and decaffeinated black tea consumption on urinary and fecal excretions and whole blood and blood serum concentrations of polyphenols. The 56 day study was divided into four randomly arranged experimental periods of 14 days each during which the 10 healthy adult subjects consumed a laboratory controlled, constant, measured diet based on ordinary foods. During separate periods, subjects received no tea, green tea, regular black tea or decaffeinated black tea beverages at the three daily meals. Subjects made complete collections of urine and stools throughout the study and fasting blood samples were drawn at the beginning of the study and at the end of each experimental period. Polyphenols contained in urine, feces, whole blood, blood serums, food and tea were analyzed by the spectrophotometry method of Wah Lau et al. (1989). Green tea consumption resulted in highest intakes in greatest fecal and urinary excretions, highest retentions, and high whole blood concentrations of polyphenols followed by effects of regular black tea, decaffeinated black tea and no tea treatments. These results indicate that polyphenols from tea are at least partly absorbable.

(1) Huang MT, et al. Effects of tea, decaffeinated tea, and caffeine on UVB light-induced complete carcinogenesis in SKH-1 mice: demonstration of caffeine as a biologically important constituent of tea. Cancer Res 1997;57:2623-9

(2) He YH, Kies C. Green and black tea consumption by humans: impact on polyphenol concentrations in feces, blood, and urine. Plant Foods Hum Nutr 1994;46:221-9

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