Background Dietary nitrate supplementation, usually in the form of beetroot juice, may improve exercise performance and endothelial function. We undertook a systematic review and meta-analysis to establish whether this approach has beneficial effects in people with respiratory disease. Methods A systematic search of records up to March 2021 was performed on PubMed, CINAHL, MEDLINE (Ovid), Cochrane and Embase to retrieve clinical trials that evaluated the efficacy of dietary nitrate supplementation on cardiovascular parameters and exercise capacity in chronic respiratory conditions. Two authors independently screened titles, abstracts and full texts of potential studies and performed the data extraction. Results After full-text review of 67 papers, eleven (two randomised controlled trials and nine crossover trials) involving 282 participants met the inclusion criteria. Three were single dose; seven short term; and one, the largest (n=122), done in the context of pulmonary rehabilitation. Pooled analysis showed that dietary nitrate supplementation reduced systolic blood pressure (BP), diastolic BP and mean arterial pressure (mean difference (95% CI), −3.39 mm Hg (−6.79 to 0.01); p=0.05 and –2.20 mm Hg (−4.36 to −0.03); p=0.05 and −4.40 mm Hg (−7.49 to −1.30); p=0.005, respectively). It was associated with increased walk distance in the context of pulmonary rehabilitation (standardised mean difference (95% CI), 0.47 (0.11 to 0.83), p=0.01), but no effect was identified in short-term studies (0.08 (−0.32 to 0.49). Conclusion Dietary nitrate supplementation may have a beneficial effect on BP and augment the effect of pulmonary rehabilitation on exercise capacity. Short-term studies do not suggest a consistent benefit on exercise capacity. PROSPERO registration number CRD42019130123. All data relevant to the study are included in the article or uploaded as supplementary information.

中文翻译：

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膳食硝酸盐补充剂对慢性呼吸系统疾病运动能力和心血管参数的影响：系统评价和荟萃分析

背景膳食硝酸盐补充剂，通常以甜菜根汁的形式，可以改善运动表现和内皮功能。我们进行了系统评价和荟萃分析，以确定这种方法是否对呼吸系统疾病患者有益。方法 在 PubMed、CINAHL、MEDLINE (Ovid)、Cochrane 和 Embase 上对截至 2021 年 3 月的记录进行系统搜索，以检索评估膳食硝酸盐补充剂对慢性呼吸系统疾病中心血管参数和运动能力功效的临床试验。两位作者独立筛选潜在研究的标题、摘要和全文并进行数据提取。结果 全文审阅 67 篇论文后，11 项（两项随机对照试验和九项交叉试验）涉及 282 名参与者符合纳入标准。三是单次给药；七短期；一个是最大的（n=122），是在肺康复的背景下完成的。汇总分析表明，膳食硝酸盐补充剂可降低收缩压 (BP)、舒张压和平均动脉压（平均差（95% CI），-3.39 mm Hg（-6.79 至 0.01）；p=0.05 和 –2.20 mm Hg（ -4.36 至 -0.03)；p=0.05 和 -4.40 毫米汞柱（分别为 -7.49 至 -1.30；p=0.005）。它与肺康复背景下步行距离的增加有关（标准化平均差（95% CI），0.47（0.11 至 0.83），p=0.01），但在短期研究中没有发现影响（0.08（-0.32到 0.49）。结论 膳食硝酸盐补充剂可能对血压有益，并增强肺康复对运动能力的影响。短期研究并未表明对运动能力的持续益处。PROSPERO 注册号 CRD42019130123。与研究相关的所有数据都包含在文章中或作为补充信息上传。