Decentralization and Local Governance I. Economic Policy I. Any ANY Methodological Briefs cover the range of options and elements available in conducting sound research and delivering reliable results. They cover impact evaluation, strategies and causal attributions and different data collection and analysis methods. Rogers, Patricia Causal attribution investigates the causal links between an intervention and observed changes and is an essential element of impact evaluation. Comparative case studies are a non-experimental impact evaluation design, which involves the analysis and synthesis of the similarities, differences and patterns across two or more cases that share a common focus, in order to answer causal questions.
Evaluative criteria specify the values that will be used to judge the merit of an intervention. Evaluative reasoning is the process of synthesizing the answers to lower- and mid-level evaluation questions into defensible judgements that directly answer the key evaluation questions. Jane Davidson. Diets including food products rich in inorganic nitrate are associated with lower blood pressure BP.
The evidence for the BP-lowering effects of inorganic nitrate and beetroot in randomized clinical trials has not been systematically assessed. The objective was to conduct a systematic review and meta-analysis of randomized clinical trials that examined the effects of inorganic nitrate and beetroot supplementation on BP. The specific inclusion criteria were: 1 randomized clinical trials; 2 trials reporting effects on systolic or diastolic BP or both; and 3 trials comparing inorganic nitrate or beetroot juice supplementation with placebo control groups. Random-effects models were used to assess the pooled BP effect sizes.
Sixteen trials met the eligibility criteria for the systematic review. All studies had a crossover study design. The duration of each intervention ranged from 2 h to 15 d. Inorganic nitrate and beetroot juice supplementation was associated with a significant reduction in systolic BP. These findings need to be tested in long-term trials and in individuals at greater cardiovascular risk.
Hypertension exceeds smoking as a causal factor in total attributable mortality 1. Therefore, nutritional and lifestyle-based interventions are unanimously recognized as important strategies for the primary prevention of hypertension and as adjuvants in pharmacological therapies to reduce cardiovascular risk 4. The Dietary Approach to Stop Hypertension DASH is one of the most effective nutritional interventions for the prevention and nonpharmacological management of hypertension 5 , 6.
The diet highlights the importance of an increased fruit and vegetable intake 7 , 8 and recent research has suggested that the beneficial effects of the DASH diet on BP are related to the high inorganic nitrate content of some of the food products included in the DASH dietary plan e.
Larsen et al. For example, Webb et al.
The BP-lowering effects of inorganic nitrate may derive from increased generation of nitric oxide NO 13 , 14 , a pleiotropic molecule involved in the vasodilation of large arteries and resistance vessels 13 , The endothelial isoform of the NO synthase uses arginine and molecular oxygen as precursors to tonically release NO in the endothelium, which is important for the control of vascular tone, smooth muscle growth, platelet aggregation, and inflammation 15 , Reduced NO bioavailability has been associated with impairment of endothelial function and increased risk of hypertension and cardiovascular diseases 17 — A nonenzymatic pathway for the generation of NO in humans has been proposed nitrate-nitrite-NO pathway , which may contribute to increased NO bioavailability Dietary and endogenous inorganic nitrate molecules may be reduced by facultative anaerobic bacteria on the dorsal surface of the tongue to nitrite, which can be chemically low pH and enzymatically xanthine oxidoreductase, myoglobin, cytochrome P, complexes of the mitochondrial electron transport chain further reduced to NO This pathway may represent a plausible mechanism to explain the beneficial effects of dietary inorganic nitrate intake on BP The main mechanistic pathways involved in the enzymatic and nonenzymatic generation of NO are described in Supplemental Figure 1.
Here, we conducted a systematic review of the evidence from randomized studies investigating the efficacy of inorganic nitrate and beetroot supplementation on BP in humans. The results will inform whether inorganic nitrate supplementation and nitrate-enriched diets could be considered as effective nutritional strategies for the prevention of hypertension and cardiovascular diseases.
The present systematic review was conducted according to established guidelines and is reported according to PRISMA guidelines Randomized clinical trials in human participants were included and the specific characteristics and designs of the trials type of placebo, parallel or crossover design, blinding of the interventions, and duration were assessed.
Studies reporting data from participants with different BMIs, ethnic backgrounds, and physical activity levels were not excluded.
Randomized clinical trials investigating the effects of inorganic nitrate or beetroot juice supplementation and providing information on the type of nitrate salt potassium or sodium nitrate , volume, formulation, frequency, and route of administration were included. Studies that delivered the nitrate or beetroot supplementation alongside another intervention e. A combined meta-analysis model was derived for inorganic nitrate solutions and beetroot juice on BP.
This approach was based on the evidence that inorganic nitrate is rapidly absorbed from the stomach and proximal small intestine with high bioavailability A crossover study was specifically conducted to determine the oral bioavailability of nitrate from spinach, lettuce, and beetroot If reported, changes in nitrate and nitrite concentrations in biological fluids plasma, urine, saliva were also assessed.
A literature search of the PubMed, Embase, and Scopus databases was undertaken from inception to February The systematic review was restricted to articles published in English. The search was conducted based on predefined search terms dietary, inorganic, nitrate, beetroot, beet root, BP, hypertension, vascular, NO, endothelial and using specific building blocks Boolean terms, truncation to create the algorithms entered in each database.
The full details of the algorithms are reported in the Supplemental Methods Box 1. Two investigators M. The first screening phase was based on the analysis of titles and abstracts. When full agreement had been reached, the article was either discarded or moved to the next phase.
In case of disagreement, the article was moved to the next phase to increase the inclusiveness level.
Reference lists of included papers and relevant reviews were searched for articles potentially missed during the electronic search. In the second phase, the full text of the selected articles was independently assessed by 2 investigators. When full agreement had been reached, the article was either discarded or moved to the next phase for full data extraction.
In case of disagreement, the article was evaluated by a third investigator J. Two investigators extracted the data using a standardized data collection form. A list of the extracted variables is provided in the Supplemental Methods Box 2.
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When BP measurements were incomplete, the corresponding authors were contacted to request the missing data. The quality of each study was assessed using the Cochrane Risk of Bias Tool 25 to assess the following domains: selection bias random sequence generation and allocation concealment , performance bias blinding of participants and personnel to which intervention a participant received , detection bias blinding of outcome assessment , attrition bias completeness of outcome data, including attrition and exclusions from the analysis , and reporting bias selective outcome reporting.
An imputed correlation value of 0. A meta-analysis was conducted using Comprehensive Meta-Analysis software Biostat. A random effect model was used to provide a more conservative estimate of the pooled effect size for diastolic and systolic BP.
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The BP differences were combined across studies using a weighted DerSimonian-Laird random effects model Forest plots were generated for graphical presentations of the BP outcomes. Additional analyses were conducted to evaluate the impact of publication bias on the effect size by removing studies with the largest effects. One study was published in abstract form only and reported a nonsignificant effect of inorganic nitrate on BP This study was not included in the meta-analysis, because full data were not available after request. Then 41 articles were selected for a full-text review and 16 studies 10 , 12 , 29 — 42 were included in the systematic review qualitative analysis after the exclusion of 25 articles.
One study was published as abstracts only However, this study matched the inclusion and exclusion criteria and it was included in the systematic review qualitative analysis but excluded from the meta-analysis quantitative analysis , because the full results on changes in BP were not available. A flow chart of the literature search is shown in Figure 1. All eligible studies used a crossover, double-blind, placebo-controlled, randomized study design.
The trials were conducted between and and included a total of participants, with 7—30 participants per individual study.
The duration of the interventions ranged from 2 h to 15 d and the washout period from 6 to 28 d. One article reported the results of 3 individual trials from which 2 trials were eligible and were entered in the final analysis The main characteristics of the studies included in the analysis are presented in Supplemental Table 1. The majority of the studies recruited young, nonsmoking, healthy participants and 2 studies were conducted in older healthy participants 38 and overweight and obese older individuals with type 2 diabetes The mean BMI of the participants ranged between Seven studies investigated the effects of inorganic nitrate and beetroot juice on exercise performance and recruited primarily young, physically active men 30 — 32 , 34 , 35 , 37 , Nitrate was dissolved either in distilled water or low-nitrate water.
The daily amount of nitrate in the beetroot juice consumed varied between 5. The choice of the placebo varied between studies and included equivalent volumes of water 3 studies 12 , 33 , 41 , isomolar potassium and sodium chloride solutions 5 studies 10 , 29 , 33 , 36 , 42 , blackcurrant juice 3 studies 30 , 31 , 37 , apple juice 1 study 39 , and nitrate-depleted beetroot juice 5 studies 32 , 34 , 35 , 38 , All solutions were given orally.
Participants were asked to refrain from consuming nitrate-enriched foods in 9 studies 10 , 12 , 30 , 31 , 33 , 35 , 36 , 41 — 42 , whereas participants were invited to maintain their prestudy dietary habits and physical activity level in 6 studies 32 , 34 , 37 — The compliance with the dietary prescriptions low-nitrate diet, habitual dietary habits was only evaluated in a few studies using diet diaries 37 of h dietary recall 34 , Resting BP was the primary outcome in 15 trials 10 , 12 , 29 — 38 , 42 and ambulatory h BP was used in 3 studies 39 — Three studies reported that the main aim of the study was concealed 30 , 31 , 37 to the study participants 30 , 31 , All studies were double blind and reported information on the duration of washout periods and dropout rates.
The order of the interventions in each trial was randomized.
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Still, Ms. Nardone said that city and state governments needed to offer more financial incentives to help buildings meet any new environmental regulations. City officials say older people and young children are particularly vulnerable to air pollution, which can irritate the lungs and worsen conditions like asthma and emphysema, as well as increase the risk of heart attack and premature death. Mindful of the health risks, the city is already converting some of its own heavy-oil-burning boilers to natural gas, after identifying city school buildings burning No.
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