Bioavailability of catechins from tea: the effect of milk

Abstract

Objectives: To assess the blood concentration of catechins following green or black tea ingestion and the effect of addition of milk to black tea. Design: Twelve volunteers received a single dose of green tea, black tea and black tea with milk in a randomized cross-over design with one-week intervals. Blood samples were drawn before and up to eight hours after tea consumption. Setting: The study was performed at the Unilever Research Vlaardingen in The Netherlands. Subjects: Twelve healthy adult volunteers (7 females, 5 males) participated in the study. They were recruited among employees of Unilever Research Vlaardingen. Interventions: Green tea, black tea and black tea with semi-skimmed milk (3 g tea solids each). Results: Consumption of green tea (0.9 g total catechins) or black tea (0.3 g total catechins) resulted in a rapid increase of catechin levels in blood with an average maximum change from baseline (CVM) of 0.46 mmol/l (13%) after ingestion of green tea and 0.10 mmol/l (13%) in case of black tea. These maximum changes were reached after (mean (s.e.m.)) t 2.3 h (0.2) and t 2.2 h (0.2) for green and black tea respectively. Blood levels rapidly declined with an elimination rate (mean (CVM)) of t 1a2 4.8 h (5%) for green tea and t 1a2 6.9 h (8%) for black tea. Addition of milk to black tea (100 ml in 600 ml) did not signi®cantly affect the blood catechin levels (areas under the curves (mean (CVM) of 0.53 h. mmol/l (11%) vs 0.60 h. mmol/l (9%) for black tea and black tea with milk respectively. Conclusion: Catechins from green tea and black tea are rapidly absorbed and milk does not impair the bioavailability of tea catechins.

A single dose of tea with or without milk increases plasma antioxidant activity in humans

“…In contrast to a previous report (Sera®ni et al, 1996) a standard addition of 10 ± 15 % of milk did not in¯uence plasma antioxidant activity in the present study. This is consistent with observations in humans showing that adding milk to black tea did not in¯uence the absorption of tea catechins (Van het Hof et al, 1998). The difference in the amount of milk added to tea might be another explanation for the discrepancy between the present study and the study of Sera®ni et al (1996), in which an amount of 26 % milk was used.…”

“…Thus, the different plasma catechin levels for green and black tea 90 min after tea consumption (ratio 5.3 : 1) clearly re¯ected the concentrations in the tea drinks (ratio 4.6 : 1). The increases observed in the present study were slightly higher or comparable to those reported by other investigators taking into account the different doses of tea used (Lee et al, 1995;Van het Hof et al, 1998;Lee et al (1995) found an average calculated maximum sum of separate catechin concentrations in plasma of 0.63 mmolaL at 4 h after consumption of 1.2 g green tea solids. Differences in results could be attributed to different methods of catechin analyses used.…”

“…Hertog et al (1997b) suggested that addition of milk to tea could be an explanation for this increased risk due to the¯avonoid binding capacity of milk proteins resulting in a reduced absorption of¯avonoids from the gastrointestinal tract. This is, however, not consistent with recent ®ndings that adding milk to black tea had no effect on the plasma concentration of catechins (Van het Hof et al, 1998).…”

Bioavailability of procyanidin dimers and trimers and matrix food effects in in vitro and in vivo models

“…Different studies have been carried out into the interaction between polyphenols and a food matrix such as milk (23,24) , olive oil (25) or sugar (26) . The evidence suggests that variations in polyphenol absorption also occur due to * Corresponding author: Dr Maria-José Motilva, fax þ34 973 702596, email motilva@tecal.udl.es Abbreviations: GSPE, grape seed procyanidin extract; IN, fraction found inside dialysis solution; OUT, fraction found outside dialysis solution; PC, procyanidins.…”

EJCN at the start of the 21st century

“…Examples of well cited work in this area comes from the Unilever Research Laboratory on sterol-enriched margarines and spreads on lipids (Westrate and Meijer, 1998;Hendriks et al, 1999) and fermented milk on the immune system (Spanhaak et al, 1998). Work on catechines in tea and chocolate is another new`hot' area (Richelle et al, 1999, van het Hof et al, 1998 that most probably will be followed by applications in novel foods. Interest in traditional food and beverages, however has not disappeared.…”