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nature publishing group
Letters to the Editor The Effect of Green Tea With Exceptionally High Catechin Content on Nadolol Plasma Concentration K Ide1, M Park1 and H Yamada1 To the Editor: We read with great interest the article “Green Tea Ingestion Greatly Reduces Plasma Concentrations of Nadolol in Healthy Subjects,” by Misaka et al.1 The authors claim that repeated ingestion of green tea reduces nadolol plasma concentrations, and suggest that green tea catechins may have an inhibitory effect on the organic anion– transporting polypeptide 1A2. There is no doubt that food–drug interaction studies on common beverages are important for developing safe pharmaceutical treatments2,3; however, this study was conducted with an atypical type of green tea and under unusual conditions. The green tea–type beverage used in this study is classed as a “Food for Specified Health Use” by the Ministry of Health, Labour, and Welfare of Japan. It contains exceptionally high total catechin content: ~540 mg/ bottle (350 ml; data obtained from Kao Corporation, Tokyo, Japan),
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constituting a total catechin concentration of 154 mg/dl. This concentration is two to five times higher than that of typical bottled green tea sold in Japan.4 This concentration is closer to that of a dietary supplement than to that of a beverage consumed for refreshment. In fact, in their article the authors do not report the total catechin concentration of the beverage. Instead, they report separate concentrations for only four types of catechins present in the beverage, despite the fact that several additional types of catechins must also have been present. This may give the impression that the beverage has a lower total catechin concentration than it actually does. The unusual design of the study also raises some concern. The study subjects took nadolol with 700 ml of the green tea beverage or water. However, it is uncommon in Japan to take medication with green tea—especially with green tea beverages that have large quantities of catechins. To ingest the same quantity of catechins consumed by subjects in this study, 2–3 liters of typical bottled green tea would have to be consumed with a single dose of nadolol. Even if the inhibitory effect observed in the authors’ in vitro study accurately reflects an effect in humans, this effect does not realistically reflect the way in which patients ordinarily take medication.
We strongly recommend further investigation into the concentrationdependent effects of green tea; however, studies that more realistically reflect actual green tea consumption patterns should provide more useful information for assessing the potential risks associated with consuming green tea. CONFLICT OF INTEREST The authors declared no conflict of interest. © 2014 ASCPT
Misaka, S. et al. Green tea ingestion greatly reduces plasma concentrations of nadolol in healthy subjects. Clin. Pharmacol. Ther. 95, 432–438 (2014). 2. Genser, D. Food and drug interaction: consequences for the nutrition/health status. Ann. Nutr. Metab. 52 (suppl. 1), 29–32 (2008). 3 . Boullata, J.I. & Hudson, L.M. Drug-nutrient interactions: a broad view with implications for practice. J. Acad. Nutr. Diet. 112, 506–517 (2012). 4. Nakagawa, S., Hoshi, T., Kubo, A., Yamato, S. Determination of tea polyphenols in bottled Japanese tea drinks and differences in polyphenol content in tea leaves from different variety [In Japanese]. Bunseki Kagaku 62, 51–55 (2013). 1.
1Department of Drug Evaluation and Informatics, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan. Correspondence: H Yamada ([email protected])
Advance online publication 26 March 2014. doi:10.1038/clpt.2014.36
VOLUME 95 NUMBER 6 | june 2014 | www.nature.com/cpt
nature publishing group
Letters to the Editor The Effect of Green Tea With Exceptionally High Catechin Content on Nadolol Plasma Concentration K Ide1, M Park1 and H Yamada1 To the Editor: We read with great interest the article “Green Tea Ingestion Greatly Reduces Plasma Concentrations of Nadolol in Healthy Subjects,” by Misaka et al.1 The authors claim that repeated ingestion of green tea reduces nadolol plasma concentrations, and suggest that green tea catechins may have an inhibitory effect on the organic anion– transporting polypeptide 1A2. There is no doubt that food–drug interaction studies on common beverages are important for developing safe pharmaceutical treatments2,3; however, this study was conducted with an atypical type of green tea and under unusual conditions. The green tea–type beverage used in this study is classed as a “Food for Specified Health Use” by the Ministry of Health, Labour, and Welfare of Japan. It contains exceptionally high total catechin content: ~540 mg/ bottle (350 ml; data obtained from Kao Corporation, Tokyo, Japan),
588
constituting a total catechin concentration of 154 mg/dl. This concentration is two to five times higher than that of typical bottled green tea sold in Japan.4 This concentration is closer to that of a dietary supplement than to that of a beverage consumed for refreshment. In fact, in their article the authors do not report the total catechin concentration of the beverage. Instead, they report separate concentrations for only four types of catechins present in the beverage, despite the fact that several additional types of catechins must also have been present. This may give the impression that the beverage has a lower total catechin concentration than it actually does. The unusual design of the study also raises some concern. The study subjects took nadolol with 700 ml of the green tea beverage or water. However, it is uncommon in Japan to take medication with green tea—especially with green tea beverages that have large quantities of catechins. To ingest the same quantity of catechins consumed by subjects in this study, 2–3 liters of typical bottled green tea would have to be consumed with a single dose of nadolol. Even if the inhibitory effect observed in the authors’ in vitro study accurately reflects an effect in humans, this effect does not realistically reflect the way in which patients ordinarily take medication.
We strongly recommend further investigation into the concentrationdependent effects of green tea; however, studies that more realistically reflect actual green tea consumption patterns should provide more useful information for assessing the potential risks associated with consuming green tea. CONFLICT OF INTEREST The authors declared no conflict of interest. © 2014 ASCPT
Misaka, S. et al. Green tea ingestion greatly reduces plasma concentrations of nadolol in healthy subjects. Clin. Pharmacol. Ther. 95, 432–438 (2014). 2. Genser, D. Food and drug interaction: consequences for the nutrition/health status. Ann. Nutr. Metab. 52 (suppl. 1), 29–32 (2008). 3 . Boullata, J.I. & Hudson, L.M. Drug-nutrient interactions: a broad view with implications for practice. J. Acad. Nutr. Diet. 112, 506–517 (2012). 4. Nakagawa, S., Hoshi, T., Kubo, A., Yamato, S. Determination of tea polyphenols in bottled Japanese tea drinks and differences in polyphenol content in tea leaves from different variety [In Japanese]. Bunseki Kagaku 62, 51–55 (2013). 1.
1Department of Drug Evaluation and Informatics, Graduate School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan. Correspondence: H Yamada ([email protected])
Advance online publication 26 March 2014. doi:10.1038/clpt.2014.36
VOLUME 95 NUMBER 6 | june 2014 | www.nature.com/cpt
