Br J Nutr. 2002 Apr;87(4):343-55.

Green tea extract only affects markers of oxidative status
postprandially: lasting antioxidant effect of flavonoid-free diet.

Young JF, Dragstedt LO, Haraldsdóttir J, Daneshvar B, Kall MA, Loft S,
Nilsson L, Nielsen SE, Mayer B, Skibsted LH, Huynh-Ba T, Hermetter A,
Sandström B.
Research Department of Human Nutrition, Royal Veterinary and
Agricultural University, Frederiksberg, Denmark.

Epidemiological studies suggest that foods rich in flavonoids might
reduce the risk of cardiovascular disease and cancer. The objective of
the present study was to investigate the effect of green tea extract
(GTE) used as a food antioxidant on markers of oxidative status after
dietary depletion of flavonoids and catechins. The study was designed
as a 2 x 3 weeks blinded human cross-over intervention study (eight
smokers, eight non-smokers) with GTE corresponding to a daily intake
of 18.6 mg catechins/d. The GTE was incorporated into meat patties and
consumed with a strictly controlled diet otherwise low in flavonoids.
GTE intervention increased plasma antioxidant capacity from 1.35 to
1.56 (P<0.02) in postprandially collected plasma, most prominently in
smokers. The intervention did not significantly affect markers in
fasting blood samples, including plasma or haemoglobin protein
oxidation, plasma oxidation lagtime, or activities of the erythrocyte
superoxide dismutase, glutathione peroxidase, glutathione reductase
and catalase. Neither were fasting plasma triacylglycerol,
cholesterol, alpha-tocopherol, retinol, beta-carotene, or ascorbic
acid affected by intervention. Urinary 8-oxo-deoxyguanosine excretion
was also unaffected. Catechins from the extract were excreted into
urine with a half-life of less than 2 h in accordance with the short-
term effects on plasma antioxidant capacity. Since no long-term
effects of GTE were observed, the study essentially served as a fruit
and vegetables depletion study. The overall effect of the 10-week
period ********** without dietary fruits and vegetables was a decrease
in oxidative damage to DNA, blood proteins, and plasma lipids,
concomitantly with marked changes in antioxidative defence.
************
PMID: 12064344

Eur J Nutr. 1999 Jun;38(3):149-57.

Green tea extract decreases plasma malondialdehyde concentration but
does not affect other indicators of oxidative stress, nitric oxide
production, or hemostatic factors during a high-linoleic acid diet in
healthy females.

Freese R, Basu S, Hietanen E, Nair J, Nakachi K, Bartsch H, Mutanen M.
Division of Nutrition, University of Helsinki, Finland.

BACKGROUND: Green tea contains polyphenolic catechins which can act as
antioxidants and thus decrease the risk for cardiovascular diseases.
AIM OF THE STUDY: To investigate whether green tea extract differs
from placebo in its effects on markers of antioxidant status, lipid
peroxidation, nitric oxide production, thromboxane production, and
blood coagulation during a controlled high linoleic acid diet in
healthy subjects. METHODS: Twenty healthy non-smoking females (23-50
years) participated in a 4-week controlled intervention study. The
experimental diet was rich in linoleic acid (9 en%) and contained fat,
protein, and carbohydrates: 27, 14, and 59 en%, respectively. In
addition, the subjects ingested encapsulated green tea extract (3 g/d)
or placebo mixture in a double-blind manner. Fasting blood samples and
five 24-hour urines were collected before and at the end of the 4-week
experimental period. Same samples were received from 10 control
subjects. RESULTS: Green tea extract significantly decreased plasma
malondialdehyde (MDA) concentration in comparison with the placebo
treatment. The treatments did not differ in serum lipids, indicators
of antioxidant status, urinary 8-isoprostaglandin F2 alpha, 2,3-
dinorthromboxane B2, nitric oxide metabolites or coagulation
indicators. CONCLUSIONS: We conclude that an amount of green tea
extract which corresponds to 10 cups of tea per day for 4 weeks does
not have specific effects on several indicators related to risk of
cardiovascular diseases in comparison with placebo treatment. The
relatively small but significant decrease in lipid peroxidation
indicated by decreased plasma MDA was not associated with changes in
markers of oxidative stress (urinary 8-isoprostaglandin F2 alpha and
blood oxidized glutathione) or hemostasis.
PMID: 10443337

Eur J Nutr. 2006 Mar;45(2):113-22. Epub 2005 Jul 20.

The effects of cranberry juice consumption on antioxidant status and
biomarkers relating to heart disease and cancer in healthy human
volunteers.

Duthie SJ, Jenkinson AM, Crozier A, Mullen W, Pirie L, Kyle J, Yap LS,
Christen P, Duthie GG.
Phytochemicals and Genomic Stability Group, Rowett Research Institute,
Greenburn Road, Bucksburn, Aberdeen (Sco) AB21 9SB, UK.

BACKGROUND: Consumption of fruit and vegetables is associated with a
decreased risk of heart disease and cancer.This has been ascribed in
part to antioxidants in these foods inactivating reactive oxygen
species involved in initiation or progression of these diseases. Non-
nutritive anthocyanins are present in significant amounts in the human
diet. However, it is unclear whether they have health benefits in
humans. AIM: To determine whether daily consumption of anthocyanin-
rich cranberry juice could alter plasma antioxidant activity and
biomarkers of oxidative stress. METHODS: 20 healthy female volunteers
aged 18-40 y were recruited. Subjects consumed 750 ml/day of either
cranberry juice or a placebo drink for 2 weeks. Fasted blood and urine
samples were obtained over 4 weeks. The total phenol, anthocyanin and
catechin content of the supplements and plasma were measured.
Anthocyanin glycosides were identified by tandem mass spectrometry (MS-
MS). Vitamin C, homocysteine (tHcy) and reduced glutathione (GSH) were
measured by HPLC. Total antioxidant ability was determined using
electron spin resonance (ESR) spectrometry and by the FRAP assay.
Plasma total cholesterol, high density lipoprotein (HDL), and low
density lipoprotein (LDL) cholesterol and triglycerides (TG) were
measured. Glutathione peroxidase (GSH-Px), catalase (CAT) and
superoxide dismutase (SOD) activities were measured in erythrocytes.
Urine was collected for analysis of malondialdehyde (MDA) by HPLC and
8-oxo-deoxyguanosine (8-oxo-dG) by ELISA. Endogenous and induced DNA
damage were measured by single cell gel electrophoresis (SCGE) in
lymphocytes. RESULTS: Vitamin C, total phenol, anthocyanin and
catechin concentrations and FRAP and ESR values were significantly
higher in the cranberry juice compared with the placebo. Cyanidin and
peonidin glycosides comprised the major anthocyanin metabolites
[peonidin galactoside (29.2%) > cyanidin arabinoside (26.1%) >
cyanidin galactoside (21.7%) > peonidin arabinoside (17.5%) > peonidin
glucoside (4.1%) > cyanidin glucoside (1.4 %)]. Plasma vitamin C
increased significantly (P<0.01) in volunteers consuming cranberry
juice. No anthocyanins (plasma) or catechins (plasma or urine) were
detectable and plasma total phenols, tHcy,TC,TG,HDL and LDL were
unchanged. The antioxidant potential of the plasma, GSH-Px, CAT and
SOD activities, and MDA were similar for both groups. Supplementation
with cranberry juice did not affect 8-oxo-deoxyguanosine in urine or
endogenous or H(2)O(2)-induced DNA damage in lymphocytes. CONCLUSIONS:
Cranberry juice consumption did not alter blood or cellular
antioxidant status or several biomarkers of lipid status pertinent to
heart disease. Similarly, cranberry juice had no effect on basal or
induced oxidative DNA damage. These results show the importance of
distinguishing between the in vitro and in vivo antioxidant activities
of dietary anthocyanins in relation to human health.
PMID: 16032375