***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Green tea polyphenols ( GTPs ) have significant antioxidant and antiinflammatory activities , and prior short‐term studies suggest that these compounds may improve photoaging skin . OBJECTIVES To evaluate the long‐term effects of oral GTPs on the clinical and histologic characteristics of photoaging skin . MATERIAL S AND METHODS Double‐blind , placebo‐controlled trial of 56 women aged 25 to 75 r and omized to 250 mg GTPs or placebo twice daily for 2 years . A blinded dermatologist scored the appearance of photodamaged facial skin at 0 , 6 , 12 , and 24 months . A blinded dermatopathologist scored the histologic characteristics of sun‐exposed arm skin at 0 and 24 months . RESULTS Clinical assessment of facial skin revealed that the GTP group had significant improvement in overall solar damage at 6 months ( p=.02 ) and significant improvement in erythema and telangiectasias at 12 months ( p=.02 ) . The placebo group did not have significant improvements in these parameters at 6 months or 12 months . There were no statistically significant differences in other photoaging parameters at 6 , 12 , or 24 months in the GTP or placebo groups . Histopathologic analysis of sunexposed arm skin showed no statistically significant difference in photoaging parameters in the GTP group or the placebo group at 24 months . CONCLUSIONS Long‐term supplementation with oral GTPs was not superior to placebo in improving clinical or histologic photoaging parameters after 24 months of use . Funding and material s for this study were provided by Nu Skin , Provo , Utah . Dale Kern is an employee of Nu Skin International Green tea ( GT ) consumption is known to be associated with enhanced cardiovascular and metabolic health . The purpose of this study is to examine the hypothesis that supplementation with GT alters insulin resistance and associated cardiovascular risk factors in obese , hypertensive patients . In a double-blind , placebo-controlled trial , 56 obese , hypertensive subjects were r and omized to receive a daily supplement of 1 capsule that contained either 379 mg of GT extract ( GTE ) or a matching placebo , for 3 months . At baseline and after 3 months of treatment , the anthropometric parameters , blood pressure , plasma lipid levels , glucose levels , creatinine levels , tumor necrosis factor α levels , C-reactive protein levels , total antioxidant status , and insulin levels were assessed . Insulin resistance was evaluated according to the homeostasis model assessment -insulin resistance protocol . After 3 months of supplementation , both systolic and diastolic blood pressures had significantly decreased in the GTE group as compared with the placebo group ( P < .01 ) . Considerable ( P < .01 ) reductions in fasting serum glucose and insulin levels and insulin resistance were observed in the GTE group when compared with the placebo group . Serum tumor necrosis factor α and C-reactive protein were significantly lower , whereas total antioxidant status increased in the GTE group compared with the placebo ( P < .05 ) . Supplementation also contributed to significant ( P < .05 ) decreases in the total and low-density lipoprotein cholesterol and triglycerides , but an increase in high-density lipoprotein cholesterol . In conclusion , daily supplementation with 379 mg of GTE favorably influences blood pressure , insulin resistance , inflammation and oxidative stress , and lipid profile in patients with obesity-related hypertension Epidemiological surveys suggest that a higher intake of tea may be associated with a lower risk of CHD . There is accumulating evidence that postpr and ial lipaemia makes a substantial contribution to the incidence of CHD . Our aim was , therefore , to evaluate the effect of tea catechins ( major ingredients in green tea ) on postpr and ial lipid responses in human subjects after the consumption of test meals . In a r and omized triple-crossover design , nine male subjects with mild or borderline hypertriacylglycerolaemia consumed 10 ( control ) , 224 ( moderate dose ) and 674 mg ( high dose ) of the assigned tea catechins three times each along with a st and ardized light meal consisting of a piece of bread spread with 20 g butter .  Plasma lipids were measured in the fasting state and 1 , 2 , 3 , 4 and 6 h after consuming the light meal . Results showed that , compared with the control , moderate and high doses of tea catechins reduced the incremental area under the plasma triacylglycerol curves by 15.1 and 28.7 % , respectively . Next , the rapid elevation of remnant-like particle cholesterol was significantly inhibited by a high dose of tea catechins 2 h after consuming the light meal ( P<0.01 ) . In the range of tea catechin dosages , no significant differences were observed in the postpr and ial responses for plasma total cholesterol or NEFA at any time point . In conclusion , this trial demonstrated that tea catechins attenuated the postpr and ial increase in plasma triacylglycerol levels following a fat load . These results may provide evidence for one of the possible mechanisms involved in lowering the incidence of CVD , and may prove useful in further studies on the beneficial health effects of tea drinking Dietary flavonoid intake has been reported to be inversely associated with the incidence of coronary artery disease . To clarify the possible role of tea flavonoids in the prevention of atherosclerosis , we investigated the effects of tea flavonoids on the susceptibility of low-density lipoprotein ( LDL ) to oxidative modification . In an in vitro study , catechins or theaflavins ( 25 - 400 mumol/L ) were added to plasma and incubated for 3 h at 37 degrees C. Then , the LDL fraction was separated by ultracentrifugation . The oxidizability of LDL was estimated by measuring conjugated diene , thiobarbituric acid-reactive substances ( TBARS ) , and lipid peroxides after cupric sulfate was added . TBARS and lipid peroxides in the supernates were also measured after incubation with macrophages . Catechins significantly ( P < 0.01 by ANOVA ) and dose-dependently prolonged the lag time before initiation of oxidation . Among the catechins , epigallocatechin gallate exerted the most marked effect , prolonging the oxidation lag time more than vitamin E at the same molar concentration . Theaflavins exerted stronger inhibitory effects than catechins . Macrophage-mediated LDL oxidation was also inhibited by adding these tea flavonoids to the plasma sample s. In an in vivo study , 14 healthy volunteers consumed 750 mL black tea/d for 4 wk . After the subjects had consumed tea for 4 wk , the lag time before LDL oxidation was significantly ( P < 0.01 ) prolonged from 54 to 62 min . This minor prolongation occurred despite much lower plasma flavonoids than were used in vitro . No significant change was observed in eight control volunteers . LDL exposed to tea flavonoids in vitro or in vivo reduced oxidizability . We speculate that tea flavonoids may have a role in ameliorating atherosclerosis BACKGROUND Tea has been associated with a reduced risk of  cardiovascular disease .  One proposed mechanism of this risk reduction involves inhibition of lipoprotein oxidation in vivo by antioxidant polyphenolic compounds derived from tea . However , controlled interventions uniformly failed to show that ingestion of tea can inhibit LDL oxidation ex vivo . The absence of effects in previous studies may be due to the isolation of LDL particles from polyphenolic compounds that are present in the aqueous phase of serum . OBJECTIVE The objective of this study was to examine the acute effects of ingestion of black and green tea on ex vivo Cu(2+)-induced lipoprotein oxidation without prior isolation of lipoproteins from serum . DESIGN The acute effects of 4 hot drinks-green tea and black tea ( each at a dose equivalent to 4 st and ard cups ) , water matched to the teas for caffeine content , and water-were assessed in 20 healthy men by using a Latin-square design . The lag time to lipoprotein diene formation , slope of the propagation phase of the oxidation curve , and area under the oxidation curve were calculated . Urinary concentrations of 4-O-methylgallic acid were used as a marker of uptake and metabolism of polyphenolic compounds from tea . RESULTS Significant increases in urinary 4-O-methylgallic acid for black and green tea ( P < 0 . 0001 ) were observed . Caffeine did not significantly influence lipoprotein oxidation . Compared with the water control , there was a greater lag time for black tea ( 5.4 + /- 2.9 min ; P = 0.05 ) that was of borderline significance and a similar trend for green tea ( 4.4 + /- 2.8 min ; P = 0.17 ) . Slope and area under the oxidation curve were not altered . CONCLUSION Black tea has a mild acute effect on ex vivo lipoprotein oxidation in human serum . 2000;71:-7 Prospect i ve studies suggest that tea may protect against cardiovascular disease . A potential mechanism for such an effect involves inhibition of lipid peroxidation by polyphenolic antioxidants derived from tea . Our objective was to determine whether regular ingestion of tea could inhibit in vivo lipid peroxidation . Two controlled intervention studies assessed the effects of regular ingestion of tea on lipid peroxidation determined by measurement of urinary F(2)-isoprostane excretion . Study 1 : The effects of 1000 mL/d of green tea and black tea were compared with hot water containing caffeine in 13 subjects with elevated blood pressure using a r and omized 3-period ( 7 d each ) crossover design . Study 2 : The effects of 1250 mL/d of black tea were compared with hot water in 22 subjects with mildly raised serum total cholesterol concentrations using a r and omized 2-period ( 4 wk each ) crossover design . F(2)-isoprostane excretion was not altered after regular ingestion of green tea ( 273 + /- 48 pmol/mmol creatinine ) or black tea ( 274 + /- 39 pmol/mmol creatinine ) in comparison with hot water ( 263 + /- 47 pmol/mmol creatinine ; Study 1 ) , or by regular ingestion of black tea ( 334 + /- 71 pmol/mmol creatinine ) in comparison with hot water ( 355 + /- 75 pmol/mmol creatinine ; Study 2 ) . These results do not support the suggestion that polyphenolic antioxidants derived from tea inhibit in vivo lipid peroxidation BACKGROUND Polyphenols can act as acceptors of methyl groups during the metabolism of methionine to homocysteine . This may result in elevations in plasma total homocysteine ( tHcy ) concentrations after ingestion of polyphenol-rich beverages such as tea . OBJECTIVES Our major objective was to determine whether regular , moderate-to-high intakes of black tea alter tHcy concentrations . We also assessed the relation between the degree of O-methylation of tea-derived polyphenols and the change in tHcy with regular ingestion of tea . DESIGN Twenty-two subjects completed a r and omized , controlled crossover study . Subjects consumed 1250 mL black tea/d ( 5 cups each containing 2 g tea leaves in 250 mL boiled water ) and 1250 mL hot water/d for 4 wk each . Fasting tHcy concentrations and 24-h urinary excretion of 4-O-methylgallic acid ( 4OMGA , the major O-methylated metabolite of gallic acid ) were measured at the end of each period . 4OMGA was used as a marker of overall O-methylation of tea-derived polyphenols . RESULTS Black tea did not significantly alter mean ( + /- SEM ) tHcy concentrations ( 9.9 + /- 0.5 and 10.0 + /- 0.5 micro mol/L for the hot water and black tea periods , respectively ) . However , the increased excretion of 4OMGA as a consequence of black tea consumption was positively associated with the change in tHcy from the hot water period to the black tea period ( r = 0.55 , P = 0.008 ) . Subjects in the bottom quartile of increase in 4OMGA excretion had a significant decrease in tHcy ( -0.28 + /- 0.10 micro mol/L ; P = 0.046 ) , and those in the top quartile had a significant increase in tHcy ( 0.78 + /- 0.16 micro mol/L ; P = 0.005 ) . CONCLUSIONS Overall , regular ingestion of black tea did not alter mean tHcy concentrations . However , individual differences in O-methylation of polyphenolic compounds may influence the ultimate effects of black tea on tHcy Despite epidemiological evidence that tea consumption is associated with the reduced risk of coronary heart disease , experimental studies design ed to show that tea affects oxidative stress or blood cholesterol concentration have been unsuccessful . We assessed the effects of black tea consumption on lipid and lipoprotein concentrations in mildly hypercholesterolemic adults .  Tea and other beverages were included in a carefully controlled weight-maintaining diet 
    Output:
    
There are very few long-term studies to date examining green or black tea for the primary prevention of CVD .