School of Human Movement and Nutrition Sciences, University of Queensland, St. Lucia, QLD, Australia.
School of Exercise and Nutrition Sciences, Queensland University of Technology, Kelvin Grove, QLD, Australia.
Sports Med. 2017 Apr;47(4):735-756. doi: 10.1007/s40279-016-0617-7.
Recent research into the use of dietary nitrates and their role in vascular function has led to it becoming progressively more popular amongst athletes attempting to enhance performance.
The objective of this review was to perform a systematic review and meta-analysis of the literature to evaluate the effect of dietary nitrate (NO) supplementation on endurance exercise performance. An additional aim was to determine whether the performance outcomes are affected by potential moderator variables.
Relevant databases such as Cochrane Library, Embase, PubMed, Ovid, Scopus and Web of Science were searched for the following search terms 'nitrates OR nitrate OR beetroot OR table beet OR garden beet OR red beet AND exercise AND performance' from inception to October 2015.
Studies were included if a placebo versus dietary nitrate-only supplementation protocol was able to be compared, and if a quantifiable measure of exercise performance was ≥30 s (for a single bout of exercise or the combined total for multiple bouts).
The literature search identified 1038 studies, with 47 (76 trials) meeting the inclusion criteria. Data from the 76 trials were extracted for inclusion in the meta-analysis. A fixed-effects meta-analysis was conducted for time trial (TT) (n = 28), time to exhaustion (TTE) (n = 22) and graded-exercise test (GXT) (n = 8) protocols. Univariate meta-regression was used to assess potential moderator variables (exercise type, dose duration, NO type, study quality, fitness level and percentage nitrite change).
Pooled analysis identified a trivial but non-significant effect in favour of dietary NO supplementation [effect size (ES) = -0.10, 95 % Cl = -0.27 to 0.06, p > 0.05]. TTE trials had a small to moderate statistically significant effect in favour of dietary NO supplementation (ES = 0.33, 95 % Cl = 0.15-0.50, p < 0.01). GXT trials had a small but non-significant effect in favour of dietary NO supplementation in GXT performance measures (ES = 0.25, 95 % Cl = -0.06 to 0.56, p > 0.05). No significant heterogeneity was detected in the meta-analysis. No statistically significant effects were observed from the meta-regression analysis.
Dietary NO supplementation is likely to elicit a positive outcome when testing endurance exercise capacity, whereas dietary NO supplementation is less likely to be effective for time-trial performance. Further work is needed to understand the optimal dosing strategies, which population is most likely to benefit, and under which conditions dietary nitrates are likely to be most effective for performance.
最近对膳食硝酸盐及其在血管功能中的作用的研究越来越受到试图提高运动表现的运动员的欢迎。
本综述的目的是对文献进行系统评价和荟萃分析，以评估膳食硝酸盐（NO）补充对耐力运动表现的影响。另一个目的是确定潜在的调节变量是否会影响结果。
从开始到 2015 年 10 月，检索了 Cochrane 图书馆、Embase、PubMed、Ovid、Scopus 和 Web of Science 等相关数据库，使用以下搜索词“硝酸盐或硝酸盐或甜菜或食用甜菜或花园甜菜或红甜菜和运动和表现”进行搜索。
如果能够比较安慰剂与膳食硝酸盐单独补充方案，并且可以量化运动表现测量值≥30 秒（单次运动或多次运动的总和），则纳入研究。
文献检索确定了 1038 项研究，其中 47 项（76 项试验）符合纳入标准。从 76 项试验中提取数据进行荟萃分析。对时间试验（TT）（n=28）、耐力试验（TTE）（n=22）和分级运动试验（GXT）（n=8）方案进行固定效应荟萃分析。使用单变量荟萃回归评估潜在的调节变量（运动类型、剂量持续时间、NO 类型、研究质量、健康水平和亚硝酸盐变化百分比）。
荟萃分析发现，膳食 NO 补充有轻微但无统计学意义的优势[效应大小（ES）=-0.10，95%置信区间（CI）=-0.27 至 0.06，p>0.05]。TTE 试验中，膳食 NO 补充具有较小到中等的统计学显著优势（ES=0.33，95%CI=0.15-0.50，p<0.01）。GXT 试验中，膳食 NO 补充对 GXT 性能指标有较小但无统计学意义的影响（ES=0.25，95%CI=-0.06 至 0.56，p>0.05）。荟萃分析中未检测到显著的异质性。荟萃回归分析未观察到统计学意义的影响。
膳食 NO 补充可能在测试耐力运动能力时产生积极的结果，而膳食 NO 补充对时间试验性能的效果可能较小。需要进一步研究以了解最佳剂量策略，最有可能受益的人群以及在何种条件下膳食硝酸盐对性能最有效。
