No Effect of Consumption of Green and Black Tea on Plasma Lipid and Antioxidant Levels and on LDL Oxidation in Smokers

Abstract

Abstract-Intake of flavonoids is associated with a reduced cardiovascular risk. Oxidation of LDL is a major step in atherogenesis, and antioxidants may protect LDL from oxidation. Because tea is an important source of flavonoids, which are strong antioxidants, we have assessed in a randomized, placebo-controlled study the effect of consumption of black and green tea and of intake of isolated green tea polyphenols on LDL oxidation ex vivo and on plasma levels of antioxidants and lipids. Healthy male and female smokers (aged 34Ϯ12 years, 13 to 16 per group) consumed during a 4-week period 6 cups (900 mL) of black or green tea or water per day, or they received as a supplement 3.6 grams of green tea polyphenols per day (equivalent to the consumption of 18 cups of green tea per day). Consumption of black or green tea had no effect on plasma cholesterol and triglycerides, HDL and LDL cholesterol, plasma vitamins C and E, ␤-carotene, and uric acid. No differences were found in parameters of LDL oxidation. Intake of green tea polyphenols decreased plasma vitamin E significantly in that group compared with the control group (Ϫ11% Pϭ.016) but had no effect on LDL oxidation ex vivo. We conclude that consumption of black or green tea (6 cups per day) has no effect on plasma lipids and no sparing effect on plasma antioxidant vitamins and that intake of a high dose of isolated green tea polyphenols decreases plasma vitamin E. Although tea polyphenols had a potent antioxidant activity on LDL oxidation in vitro, no effect was found on LDL oxidation ex vivo after consumption of green or black tea or intake of a green tea polyphenol isolate. (Arterioscler Thromb Vasc Biol. 1998;18:833-841.)

Consumption of black and green tea has no effect on inflammation, haemostasis and endothelial markers in smoking healthy individuals

“…2.5). These levels were comparable in the four groups and did not change during the intervention period (Princen et al, 1998).…”

“…None of the participants reported any side effects. Dietary intake of antioxidants vitamin C, vitamin E, bcarotene, and¯avonoids (quercetin, myricetin and kaempferol, corrected for¯avonoids from tea) was similar before and at the end of the study (Princen et al, 1998).…”

“…The study design has been published elsewhere in detail (Princen et al, 1998). The study had a single-blind placebocontrolled parallel design.…”

Assessment of a natural dietary extract, titrated in phenylpropanoid glycosides, on blood parameters and plasma oxidative status in intensively reared Italian hares (Lepus corsicanus)

“…The increase in serum levels of vitamins A and E can be attributed to the ability of verbascoside to strengthen and save the endogenous antioxidant system, controlling oxidative metabolism by reducing the production of reactive radical species and increasing the antioxidant activity of enzymes (Princen et al, 1998;Zhu et al, 1999;Liao and Yin, 2000).…”

Absorption and antioxidant effects of quercetin from onions, in man

“…In part, this is because quercetin is not signi®cantly incorporated into the LDL particle. This would explain the ®nding of a number of recent in vivo studies which have concluded that the ingestion of tea, a beverage rich in¯avonoids, does not protect the LDL against oxidation in vivo (van het Hof et al, 1997;McAnlis et al, 1998;Princen et al, 1998). The¯avonoids may be absorbed from the tea into the plasma, as shown by Lee et al (1995), but become bound to the plasma proteins leaving them unable to protect the LDL particle against oxidation.…”