***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: Insulin resistance , a key component of the metabolic syndrome , is a risk factor for diabetes mellitus and cardiovascular disease .  Acetyl-l-carnitine infusion acutely ameliorated insulin sensitivity in type 2 diabetics with insulin resistance . In this sequential off-on-off pilot study , we prospect ively evaluated the effects of 24-week oral acetyl-l-carnitine ( 1 g twice daily ) therapy on the glucose disposal rate ( GDR ) , assessed by hyperinsulinemic euglycemic clamps , and components of the metabolic syndrome in nondiabetic subjects at increased cardiovascular risk a priori segregated into 2 groups with GDR ≤7.9 ( n=16 ) or > 7.9 ( n=16 ) mg/kg per minute , respectively .  Baseline GDR and systolic blood pressure were negatively correlated ( n=32 ; P=0.001 ; r=−0.545 ) , and patients with GDR ≤7.9 mg/kg per minute had higher systolic/diastolic blood pressure than those with higher GDR . Acetyl-l-carnitine increased GDR from 4.89±1.47 to 6.72±3.12 mg/kg per minute ( P=0.003 , Bonferroni-adjusted ) and improved glucose tolerance in patients with GDR ≤7.9 mg/kg per minute , whereas it had no effects in those with higher GDRs . Changes in GDR were significantly different between groups ( P=0.017 , ANCOVA ) . Systolic blood pressure decreased from 144.0±13.6 to 135.1±8.4 mm Hg and from 130.8±12.4 to 123.8±10.8 mm Hg in the lower and higher GDR groups , respectively ( P<0.05 for both ; P<0.001 overall ) and progressively recovered toward baseline over 8 weeks posttreatment . Total and high molecular weight adiponectin levels followed specular trends . Diastolic blood pressure significantly decreased only in those with higher GDRs . Treatment was well tolerated in all of the patients . Acetyl-l-carnitine safely ameliorated arterial hypertension , insulin resistance , impaired glucose tolerance , and hypoadiponectinemia in subjects at increased cardiovascular risk . Whether these effects may translate into long-term cardioprotection is worth investigating CONTEXT Popular diets , particularly those low in carbohydrates , have challenged current recommendations advising a low-fat , high-carbohydrate diet for weight loss . Potential benefits and risks have not been tested adequately . OBJECTIVE To compare 4 weight-loss diets representing a spectrum of low to high carbohydrate intake for effects on weight loss and related metabolic variables . DESIGN , SETTING , AND PARTICIPANTS Twelve-month r and omized trial conducted in the United States from February 2003 to October 2005 among 311 free-living , overweight/obese ( body mass index , 27 - 40 ) nondiabetic , premenopausal women . INTERVENTION Participants were r and omly assigned to follow the Atkins ( n = 77 ) , Zone ( n = 79 ) , LEARN ( n = 79 ) , or Ornish ( n = 76 ) diets and received weekly instruction for 2 months , then an additional 10-month follow-up . MAIN OUTCOME MEASURES Weight loss at 12 months was the primary outcome . Secondary outcomes included lipid profile ( low-density lipoprotein , high-density lipoprotein , and non-high-density lipoprotein cholesterol , and triglyceride levels ) , percentage of body fat , waist-hip ratio , fasting insulin and glucose levels , and blood pressure . Outcomes were assessed at months 0 , 2 , 6 , and 12 . The Tukey studentized range test was used to adjust for multiple testing . RESULTS Weight loss was greater for women in the Atkins diet group compared with the other diet groups at 12 months , and mean 12-month weight loss was significantly different between the Atkins and Zone diets ( P<.05 ) . Mean 12-month weight loss was as follows : Atkins , -4.7 kg ( 95 % confidence interval [ CI ] , -6.3 to -3.1 kg ) , Zone , -1.6 kg ( 95 % CI , -2.8 to -0.4 kg ) , LEARN , -2.6 kg ( -3.8 to -1.3 kg ) , and Ornish , -2.2 kg ( -3.6 to -0.8 kg ) . Weight loss was not statistically different among the Zone , LEARN , and Ornish groups . At 12 months , secondary outcomes for the Atkins group were comparable with or more favorable than the other diet groups . CONCLUSIONS In this study , premenopausal overweight and obese women assigned to follow the Atkins diet , which had the lowest carbohydrate intake , lost more weight at 12 months than women assigned to follow the Zone diet , and had experienced comparable or more favorable metabolic effects than those assigned to the Zone , Ornish , or LEARN diets [ corrected ] While questions remain about long-term effects and mechanisms , a low-carbohydrate , high-protein , high-fat diet may be considered a feasible alternative recommendation for weight loss . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00079573 Vegetarians have relatively low blood pressure ( BP ) levels and consume less protein than do nonvegetarians , and there have been suggestions that certain proteins may raise BP . To determine whether dietary protein supplements raise the BP of vegetarians , 58 g/per day of a 60:40 mixture of soy and wheat proteins and an isocaloric low protein supplement supplying 7 g/day of rice protein were added for 6-week periods to the diet of 18 vegetarians in a 2-group crossover design . Mean daily protein intake during consumption of the low and high protein supplements was 63 and 119 g , respectively . Mean BP was 109/72 mm Hg after the high protein and 108/71 mm Hg after the low protein diet . Consumption of other major nutrients , mean body weight , and sodium and potassium excretion did not change significantly . Thus , protein supplementation of a vegetarian diet that contained a below average but nutritionally adequate amount of protein did not significantly affect BP over 6 weeks BACKGROUND The purpose of this study was to assess relations to blood pressure ( BP ) in individuals of markers of dietary protein in their 24-hour urine collection s. METHODS AND RESULTS INTERSALT ( INTERnational study of SALT and blood pressure ) was a cross-sectional study of 10020 men and women aged 20 to 59 years in 52 population -based sample s in 32 countries worldwide , with quality -controlled st and ardized procedures and assessment of multiple possible confounders . Three measurements of dietary protein in 24-hour urine of each individual participant were studied : total nitrogen and urea as indexes of total protein intake , and sulfate as an index of sulfur-containing dietary amino acids . Repeat examination was performed in a r and om 8 % of participants to assess reliability and to correct for regression-dilution bias . Significant independent inverse relationships were found between BP ( systolic and diastolic ) and both 24-hour urinary total nitrogen and urea nitrogen , with adjustment for age , sex , alcohol intake , body mass , and 24-hour urinary sodium , potassium , calcium , and magnesium . With adjustment for regression-dilution bias , it was estimated that systolic and diastolic BP were on average 3.0 and 2.5 mm Hg lower , respectively , for persons with dietary total protein intake 30 % above the overall mean than for those whose dietary protein intake was 30 % below the overall mean ( 12.94 versus 6.96 g/d urinary total nitrogen , equivalent to 81 versus 44 g/d dietary protein , respectively ) . For the association of these markers with diastolic BP , results were similar for younger ( 20- to 39-year-old ) and older ( 40- to 59-year-old ) persons and for women and men . For their relation to systolic BP , regression coefficients were larger both for those aged 40 to 59 years than for those aged 20 to 39 years and for women than for men . Nonsignificant inverse relations were recorded for urinary sulfate and BP . CONCLUSIONS These INTERSALT findings lend support to the hypothesis that higher dietary protein intake has favorable influences on BP 1 . A r and omized , controlled trial was carried out to examine whether changes in type and amount of dietary protein were responsible for earlier observations of blood-pressure-lowering effects of lacto-ovo-vegetarian diets . 2 . Sixty-four subjects were pair-matched for sex , age , weight and sitting systolic blood pressure , and were r and omly allocated to receive one of two types of protein supplement : one containing proteins from meat , the other proteins from non-meat sources . The supplements were balanced in terms of other nutrients . Consumption of other meat , poultry or fish was prohibited . 3 . Sitting and st and ing blood pressures , weight , dietary intakes and plasma and urinary electrolytes were measured at regular intervals during the 12 weeks of trial . Urinary 3-methylhistidine was used as a measure of compliance . 4 . Fifty subjects completed the trial . There were no statistically significant blood pressure differences between groups either at baseline or at end-of-trial , neither were there any substantive differences in mean blood pressure changes between baseline and end-of-trial . 3-Methyl-histidine excretion was significantly lower in subjects on the non-meat diet . 5 . The results suggest that the protein components of the lacto-ovo-vegetarian diet are not responsible for the blood-pressure-lowering effects of that diet CONTEXT Reduced intake of saturated fat is widely recommended for prevention of cardiovascular disease . The type of macronutrient that should replace saturated fat remains uncertain . OBJECTIVE To compare the effects of 3 healthful diets , each with reduced saturated fat intake , on blood pressure and serum lipids . DESIGN , SETTING , AND PARTICIPANTS R and omized , 3-period , crossover feeding study ( April 2003 to June 2005 ) conducted in Baltimore , Md , and Boston , Mass. Participants were 164 adults with prehypertension or stage 1 hypertension . Each feeding period lasted 6 weeks and body weight was kept constant . INTERVENTIONS A diet rich in carbohydrates ; a diet rich in protein , about half from plant sources ; and a diet rich in unsaturated fat , predominantly monounsaturated fat . MAIN OUTCOME MEASURES Systolic blood pressure and low-density lipoprotein cholesterol . RESULTS Blood pressure , low-density lipoprotein cholesterol , and estimated coronary heart disease risk were lower on each diet compared with baseline . Compared with the carbohydrate diet , the protein diet further decreased mean systolic blood pressure by 1.4 mm Hg ( P = .002 ) and by 3.5 mm Hg ( P = .006 ) among those with hypertension and decreased low-density lipoprotein cholesterol by 3.3 mg/dL ( 0.09 mmol/L ; P = .01 ) , high-density lipoprotein cholesterol by 1.3 mg/dL ( 0.03 mmol/L ; P = .02 ) , and triglycerides by 15.7 mg/dL ( 0.18 mmol/L ; P<.001 ) . Compared with the carbohydrate diet , the unsaturated fat diet decreased systolic blood pressure by 1.3 mm Hg ( P = .005 ) and by 2.9 mm Hg among those with hypertension ( P = .02 ) , had no significant effect on low-density lipoprotein cholesterol , increased high-density lipoprotein cholesterol by 1.1 mg/dL ( 0.03 mmol/L ; P = .03 ) , and lowered triglycerides by 9.6 mg/dL ( 0.11 mmol/L ; P = .02 ) . Compared with the carbohydrate diet , estimated 10-year coronary heart disease risk was lower and similar on the protein and unsaturated fat diets . CONCLUSION In the setting of a healthful diet , partial substitution of carbohydrate with either protein or monounsaturated fat can further lower blood pressure , improve lipid levels , and reduce estimated cardiovascular risk . Clinical Trials Registration Clinical Trials.gov Identifier : NCT00051350 The urinary excretion of 3-methylhistidine is used as a convenient index of muscle protein catabolism . Histidine is methylated in peptide linkage within muscle protein , and is quantitatively excreted when the protein is catabolized . 3-Methylhistidine would be expected to be present in ingested muscle protein , and unless altered in the digestive process , to be excreted as a function of intake . We studied its excretion at four levels of mixed protein intake , in separate groups of obese subjects , on the 1st day of altered input , with 
    Output:
    
Results of biomarker studies and r and omized controlled trials indicated a beneficial effect of  protein on BP .
This beneficial effect may be mainly driven by plant protein , according to results in observational studies .
There was some evidence that  BP in people with elevated BP and /or older age could be more sensitive to dietary protein .
CONCLUSIONS / SIGNIFICANCE In conclusion , evidence suggests a small beneficial effect of  protein  on BP , especially for plant protein .