January 2000, Volume 54, Issue 1, Pages 87 - 92

Original Communication

A single dose of tea with or without milk increases plasma antioxidant activity in humans R Leenen, AJC Roodenburg, LBM Tijburg & SA Wiseman Unilever Nutrition Centre, Unilever Research Vlaardingen, PO Box 114, 3130 AC Vlaardingen, The Netherlands     Correspondence to: Dr. Rianne Leenen , Unilever Nutrition Centre, Unilever Research Vlaardingen, PO Box 114, 3130 AC Vlaardingen, The Netherlands.     Contributors: RL and AJCR were responsible for the design, the actual ‘living phase’ of the study and the article. SAW and LBMT had essential input in both the writing of the protocol and the article. Guarantor: Unilever Nutrition Centre.

Keywords

tea;   antioxidant activity;   milk;   catechins;   flavonoids;   bioavailability;   human study

Abstract

Objective: To investigate the effect of black and green tea consumption, with and without milk, on the plasma antioxidant activity in humans. Design: In a complete cross-over design, 21 healthy volunteers (10 male, 11 female) received a single dose of black tea, green tea (2 g tea solids in 300 ml water) or water with or without milk. Blood samples were obtained at baseline and at several time points up to 2 h post-tea drinking. Plasma was analysed for total catechins and antioxidant activity, using the ferric reducing ability of plasma (FRAP) assay. Results: Consumption of black tea resulted in a significant increase in plasma antioxidant activity reaching maximal levels at about 60 min. A larger increase was observed after consumption of green tea. As anticipated from the higher catechin concentration in green tea, the rise in plasma total catechins was significantly higher after consumption of green tea when compared to black tea. Addition of milk to black or green tea did not affect the observed increases in plasma antioxidant activity. Conclusions: Consumption of a single dose of black or green tea induces a significant rise in plasma antioxidant activity in vivo. Addition of milk to tea does not abolish this increase. Whether the observed increases in plasma antioxidant activity after a single dose of tea prevent in vivo oxidative damage remains to be established. European Journal of Clinical Nutrition (2000) 54, 87-92

Received 23 March 1999; Revised 16 July 1999; Accepted 9 August 1999

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