***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 —Endothelial function is impaired in coronary artery disease and may contribute to its clinical manifestations . Increased oxidative stress has been linked to impaired endothelial function in atherosclerosis and may play a role in the pathogenesis of cardiovascular events . This study was design ed to determine whether endothelial dysfunction and vascular oxidative stress have prognostic impact on cardiovascular event rates in patients with coronary artery disease . Methods and Results —Endothelium-dependent and -independent vasodilation was determined in 281 patients with documented coronary artery disease by measuring forearm blood flow responses to acetylcholine and sodium nitroprusside using venous occlusion plethysmography . The effect of the coadministration of vitamin C ( 24 mg/min ) was assessed in a subgroup of 179 patients .  Cardiovascular events , including death from cardiovascular causes , myocardial infa rct ion , ischemic stroke , coronary angioplasty , and coronary or peripheral bypass operation , were studied during a mean follow-up period of 4.5 years . Patients experiencing cardiovascular events ( n=91 ) had lower vasodilator responses to acetylcholine ( P < 0.001 ) and sodium nitroprusside ( P < 0.05 ) , but greater benefit from vitamin C ( P < 0.01 ) . The Cox proportional regression analysis for conventional risk factors demonstrated that blunted acetylcholine-induced vasodilation ( P = 0.001 ) , the effect of vitamin C ( P = 0.001 ) , and age ( P = 0.016 ) remained independent predictors of cardiovascular events . Conclusions —Endothelial dysfunction and increased vascular oxidative stress predict the risk of cardiovascular events in patients with coronary artery disease . These data support the concept that oxidative stress may contribute not only to endothelial dysfunction but also to coronary artery disease activity OBJECTIVES The study was done to determine whether radial artery applanation tonometry can be used as a noninvasive method of assessing global endothelial function . BACKGROUND ; It is known that beta(2)-receptor stimulation results in endothelial release of nitric oxide . Furthermore , for over a century glyceryl trinitrate ( GTN ) has been known to markedly affect the arterial pressure waveform , even in the absence of significant blood pressure ( BP ) changes . Therefore , it was hypothesized that the change in the peripheral pressure waveform , as measured using tonometry and quantified using the augmentation index ( AIx ) and in response to Salbutamol ( Salb ) , would allow assessment of global endothelial function . METHODS The study contained three parts . In the first study , Salb ( 400 microg ) was administered to 11 healthy subjects via inhalation after either intravenous N-omega-nitro-monomethyl-L-arginine ( L-NMMA ) ( 3 mg/kg over 5 min ) or control solution ( normal saline ) in the supine , rested , fasted condition . The BP , heart rate and waveform responses were recorded each 5 min following Salb for 20 min . Next , GTN was given and responses recorded 5 min later . In the second study , both the reproducibility of Salb and the GTN responses were assessed in 9 subjects studied twice on separate days . In the third study , the Salb and GTN responses of 12 subjects with angiographic coronary artery disease ( CAD ) were compared with 10 age-matched control subjects with no atherosclerotic risk factors . RESULTS After control infusion , AIx decreased following Salb , from 50.8 + /- 4.3 % to 44.8 + /- 4.2 % , a change of -11.8 + /- 3.7 % , p < 0.01 . After L-NMMA , AIx did not significantly change following Salb ( 54.2 + /- 5.1 % vs. 52.9 + /- 5.3 % , -2.0 + /- 3.1 % ) . The GTN-induced decreases in AIx were similar after either infusion ( 35.1 + /- 3.3 % vs. 36.5 + /- 3.3 % ) . Reproducibility of Salb-induced changes in AIx between studies performed on separate days was good ( r = 0.80 , p < 0.01 ) . Salb-induced changes in AIx in CAD patients were significantly less compared to control subjects ( -2.4 + /- 1.9 % vs. -13.2 + /- 2.4 % , respectively , p < 0.002 ) . The GTN-induced changes were not significantly different ( -27.6 + /- 4.2 vs. -38.9 + /- 4.4 % , p = 0.07 ) . CONCLUSIONS The peripheral arterial pressure waveform is sensitive to beta(2)-stimulation . Changes are related to nitric oxide release , are reproducible and can distinguish between clinical subject groups . Arterial waveform changes following Salb may thus provide a noninvasive method of measuring " global " arterial endothelial function Epidemiological studies indicate that diets rich in fruits and vegetables ( F&V ) are protective against CVD .  Puréed F&V products retain many beneficial components , including flavonoids , carotenoids , vitamin C and dietary fibres . The present study aim ed to establish the physiological effects of acute ingestion of a F&V purée-based drink ( FVPD ) on vasodilation , antioxidant status , phytochemical bioavailability and other CVD risk factors . A total of twenty-four subjects , aged 30 - 70 years , completed the r and omised , single-blind , controlled , crossover test meal study . Subjects consumed 400 ml of the FVPD , or a fruit-flavoured sugar-matched control , after following a low-flavonoid diet for 5 d. Blood and urine sample s were collected throughout the study day , and vascular reactivity was assessed at 90 min intervals using laser Doppler iontophoresis . The FVPD significantly increased plasma vitamin C ( P= 0·002 ) and total nitrate/nitrite ( P= 0·001 ) concentrations . There was a near significant time by treatment effect on ex vivo LDL oxidation ( P= 0·068 ) , with a longer lag phase after consuming the FVPD . During the 6 h after juice consumption , the antioxidant capacity of plasma increased significantly ( P= 0·003 ) and there was a simultaneous increase in plasma and urinary phenolic metabolites ( P < 0·05 ) . There were significantly lower glucose and insulin peaks after ingestion of the FVPD compared with control ( P= 0·019 and 0·003 ) and a trend towards increased endothelium-dependent vasodilation following FVPD consumption ( P= 0·061 ) . Overall , FVPD consumption significantly increased plasma vitamin C and total nitrate/nitrite concentrations , with a trend towards increased endothelium-dependent vasodilation  . Puréed F&V products are useful vehicles for increasing micronutrient status , plasma antioxidant capacity and in vivo NO generation , which may contribute to CVD risk reduction Background — Observational evidence has consistently linked increased fruit and vegetable consumption with reduced cardiovascular morbidity ; however , there is little direct trial evidence to support the concept that fruit and vegetable consumption improves vascular function . This study assessed the dose-dependent effects of a fruit and vegetable intervention on arterial health in subjects with hypertension . Methods and Results — After a 4-week run-in period during which fruit and vegetable intake was limited to 1 portion per day , participants were r and omized to consume either 1 , 3 , or 6 portions daily for the next 8 weeks . Endothelium-dependent and -independent arterial vasodilator responses were assessed by venous occlusion plethysmography in the brachial circulation before and after intervention . Compliance was monitored with serial contemporaneous 4-day food records and by measuring concentrations of circulating dietary biomarkers . A total of 117 volunteers completed the 12-week study . Participants in the 1- , 3- , and 6-portions/d groups reported consuming on average 1.1 , 3.2 , and 5.6 portions of fruit and vegetables , respectively , and serum concentrations of lutein and & bgr;-cryptoxanthin increased across the groups in a dose-dependent manner . For each 1-portion increase in reported fruit and vegetable consumption , there was a 6.2 % improvement in forearm blood flow responses to intra-arterial administration of the endothelium-dependent vasodilator acetylcholine ( P=0.03 ) . There was no association between increased fruit and vegetable consumption and vasodilator responses to sodium nitroprusside , an endothelium-independent vasodilator . Conclusions — The present study illustrates that among hypertensive volunteers , increased fruit and vegetable consumption produces significant improvements in an established marker of endothelial function and cardiovascular prognosis BACKGROUND Although numerous human studies have shown consistent effects of some polyphenol-rich foods on several intermediate markers for cardiovascular diseases , it is still unknown whether their action could be specifically related to polyphenols . OBJECTIVE We investigated the effect of orange juice and its major flavonoid , hesperidin , on microvascular reactivity , blood pressure , and cardiovascular risk biomarkers through both postpr and ial and chronic intervention studies . DESIGN Twenty-four healthy , overweight men ( age 50 - 65 y ) were included in a r and omized , controlled , crossover study . Throughout the three 4-wk periods , volunteers daily consumed 500 mL orange juice , 500 mL control drink plus hesperidin ( CDH ) , or 500 mL control drink plus placebo ( CDP ) . All measurements and blood collection s were performed in overnight-fasted subjects before and after the 4-wk treatment periods . The postpr and ial study was conducted at the beginning of each experimental period . RESULTS Diastolic blood pressure ( DBP ) was significantly lower after 4 wk consumption of orange juice or CDH than after consumption of CDP ( P = 0.02 ) , whereas microvascular endothelium-related reactivity was not significantly affected when measured after an overnight fast . However , both orange juice and CDH ingestion significantly improved postpr and ial microvascular endothelial reactivity compared with CDP ( P < 0.05 ) when measured at the peak of plasma hesperetin concentration . CONCLUSIONS In healthy , middle-aged , moderately overweight men , orange juice decreases DBP when regularly consumed and postpr and ially increases endothelium-dependent microvascular reactivity . Our study suggests that hesperidin could be causally linked to the beneficial effect of orange juice . This trial is registered at clinical trials.gov as NCT00983086 OBJECTIVES Our objective was to determine if long-term daily administration of phytonutrient supplements can prevent the immediate adverse impact of a high-fat meal and increase the production of nitric oxide . BACKGROUND Ingestion of a high-fat meal impairs flow-mediated vasodilation of the brachial artery for at least 4 h ; however , co-ingestion of vitamin antioxidants or a green salad has been shown to prevent this effect . METHODS Flow-mediated brachial artery reactivity test ( BART ) both before and 3 h after a 900 calorie 50 g fat meal was evaluated in 38 healthy volunteers ( age 36.4 + /- 10.1 years ) . Subjects were r and omized to four weeks of daily supplementation with a powdered fruit vegetable juice concentrate ( Juice Plus [ JP ] ) along with a complex supplement providing nutritional antioxidants and various herbal extracts ( Vineyard [ V ] ) , JP alone , or a matching placebo . At three and four weeks , BART was repeated both before and after the high-fat meal . Serum nitrate/nitrite concentrations were measured at baseline and at four weeks . RESULTS Four weeks of the JP-V combination blunted the detrimental effect of the high-fat meal ( -47.5 + /- 23.4 % at baseline vs. -1.7 + /- 9.7 % at four weeks [ p < 0.05 ] ) . Four weeks of JP alone had a similar beneficial effect ( -45.1 + /- 19.7 % at baseline vs. -16.6 + /- 10.3 % at four weeks [ p < 0.05 ] ) , whereas there was no substantial effect of the placebo . In the subjects treated with supplements , concentrations of serum nitrate/nitrite increased from 78 + /- 39 to 114 + /- 62 microm/l ( p < 0.02 ) . CONCLUSIONS Daily ingestion of modest amounts of a fruit/vegetable juice concentrate with or without adjunctive phytonutrient supplementation can reduce the immediate adverse impact of high-fat meals on flow-mediated vasoactivity and increase nitrate/nitrite blood concentration K-rich fruit and vegetables may lower blood pressure ( BP ) and improve vascular function . A r and omised controlled trial ( IS RCT N50011192 ) with a cross-over design was conducted in free-living participants with early stages of hypertension ( diastolic BP>80 and < 100 mmHg , not receiving BP-lowering medication ) to test this hypothesis . Following a 3-week run-in period on a control di 
    Output:
    
Potassium appears to improve endothelial function with a dose of > 40 mmol/d , however the mechanisms for this effect remain unclear .
Potassium may improve measures of vascular function however this effect may be dependent on the effect of potassium on blood pressure .
The effect of fruit and vegetables on endothelial function independent of confounding variables is less clear .
Increased fruit and vegetable intake may improve vascular function only in high risk population s. CONCLUSION Increasing dietary potassium appears to improve vascular function but the effect of increasing fruit and vegetable intake per se on vascular function is less clear