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Reply to K.W. Lee, H.J. Lee and C.Y. Lee

Department of Biochemistry

Y. Huang

Department of Physiology The Chinese University of Hong Kong Shatin, NT, Hong Kong

Dear Editor:

Lee and his colleague rightly emphasize that not only the types but also the concentrations of catechins and theaflavins (TF) contribute to the overall antioxidant capacity of green and black teas. Our study (1 ) compared and ranked the antioxidant activities of individual catechins and TF on an equal concentration basis.

The composition of tea varies with the three major types, i.e., green, black and oolong tea. Green tea is nonfermented tea in which catechins (EC, ECG, EGC and EGCG) are the major type of polyphenols. In black tea, catechins are oxidized and polymerized during fermentation to the brown "pigments" called TF and thearubigins (TR). Oolong tea is a semifermented product containing a mixture of catechins, TF and TR. Green tea contains the greatest concentration of catechins (100 g/kg dry tea leaves), black tea the least (<10 g/kg dry tea leaves) and oolong tea an intermediate level (50 g/kg dry tea leaves) (2 ). In contrast, black tea contains the most TF and TR, green tea the least and oolong tea an intermediate level. In terms of total polyphenols, green tea has the greatest abundance followed by oolong and black tea.

Information on the in vivo antioxidant activity of green tea compared with black tea is very limited. Serafini et al. (3 ) found that the ingestion of tea significantly increased human plasma antioxidant capacity but the potency of green tea and black tea was similar. The plasma antioxidant capacity after drinking green tea peaked at 30 min, whereas it was greatest at 50 min in subjects who drank black tea (4 ). When green tea and black tea were compared with fruit and vegetables in vitro, the antioxidant capacity of the former appeared to be greater than that of the latter (5 ). Caution must be taken in extrapolating these in vitro data to humans due to differences in bioavailability, metabolism and interactions with other nutrients. Similarly, the advantage of drinking green tea over black tea is currently unknown because the in vivo antioxidant behaviors of catechins, TF and TR have not been thoroughly studied and compared. Under the same in vitro experimental conditions, TF possessed antioxidant potency comparable to that of catechins.

Initial review completed 27 December 2001. Revision accepted 23 January 2002.

LITERATURE CITED

1. Leung, L. K., Su, Y. L., Chen, R., Zhang, Z., Huang, Y. & Chen, Z. Y. (2001) Theaflavins in black tea and catechins in green tea are equally effective antioxidants. J. Nutr. 131:2248-2251.[Abstract/Free Full Text]

2. Chen, Z. Y., Zhu, Q. Y., Tsang, D. & Huang, Y. (2001) Degradation of green tea catechins in tea drinks. J. Agric. Food Chem. 49:477-482.[Medline]

3. Sarafini, M., Ghiselli, A. & Ferro-Luzzi, A. (1996) In vivo antioxidant effect of green and black tea in man. Eur. J. Clin. Nutr. 50:28-32.[Medline]

4. Sarafini, M., Laranjinha, J. A., Almeida, L. M. & Maiani, G. (2000) Inhibition of human LDL lipid peroxidation by phenol-rich beverages and their impact on plasma total antioxidant capacity in humans. J. Nutr. Biochem. 11:585-590.[Medline]

5. du Toit, R., Volsteedt, Y. & Apostolides, Z. (2001) Comparison of the antioxidant content of fruits, vegetables and teas measured as vitamin C equivalents. Toxicology 166:63-69.[Medline]

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