Kroll Juliet L, Werchan Chelsey A, Rosenfield David, Ritz Thomas
Southern Methodist University, Dallas, TX, United States of America.
PLoS One. 2018 Jan 25;13(1):e0191030. doi: 10.1371/journal.pone.0191030. eCollection 2018.
Nitric oxide (NO) plays an important role in the airways' innate immune response, and the fraction of exhaled NO at a flow rate of 50mL per second (FENO50) has been utilized to capture NO. Deficits in NO are linked to loss of bronchoprotective effects in airway challenges and predict symptoms of respiratory infection. While beetroot juice supplements have been proposed to enhance exercise performance by increasing dietary nitrate consumption, few studies have examined the impact of beetroot juice or nitrate supplementation on airway NO in contexts beyond an exercise challenge, which we know influences FENO50.
We therefore examined the influence of a beetroot juice supplement on FENO50 in healthy males and females (n = 38) during periods of rest and in normoxic conditions. FENO50, heart rate, blood pressure, and state affect were measured at baseline, 45 minutes, and 90 minutes following ingestion of 70ml beetroot juice (6.5 mmol nitrate). Identical procedures were followed with ingestion of 70ml of water on a control day.
After beetroot consumption, average values of the natural log of FENO50 (lnFENO50) increased by 21.3% (Cohen's d = 1.54, p < .001) 45 minutes after consumption and by 20.3% (Cohen's d = 1.45, p < .001) 90 min after consumption. On the other hand, only very small increases in FENO50 were observed after consumption of the control liquid (less than 1% increase). A small subset (n = 4) of participants completed an extended protocol lasting over 3 hours, where elevated levels of FENO50 persisted. No significant changes in cardiovascular measures were observed with this small single dose of beetroot juice.
As NO serves a key role in innate immunity, future research is needed to explore the potential clinical utility of beetroot and dietary nitrate to elevate FENO50 and prevent respiratory infection.
一氧化氮（NO）在气道固有免疫反应中发挥重要作用，每秒50毫升流速时的呼出一氧化氮分数（FENO50）已被用于测定NO。NO缺乏与气道激发试验中支气管保护作用丧失有关，并可预测呼吸道感染症状。虽然有人提出甜菜根汁补充剂可通过增加膳食硝酸盐摄入量来提高运动表现，但很少有研究考察甜菜根汁或硝酸盐补充剂在运动激发试验之外的情况下对气道NO的影响，我们知道运动激发试验会影响FENO50。
因此，我们考察了甜菜根汁补充剂对38名健康男性和女性在静息和常氧条件下FENO50的影响。在摄入70毫升甜菜根汁（6.5毫摩尔硝酸盐）后的基线、45分钟和90分钟测量FENO50、心率、血压和状态情绪。在对照日摄入70毫升水时遵循相同程序。
饮用甜菜根汁后，FENO50自然对数（lnFENO50）的平均值在饮用后45分钟增加了21.3%（科恩d值=1.54，p<.001），在饮用后90分钟增加了20.3%（科恩d值=1.45，p<.001）。另一方面，饮用对照液后仅观察到FENO50非常小的增加（增加不到1%）。一小部分参与者（n=4）完成了一项持续超过3小时的扩展方案，其中FENO50水平持续升高。饮用这一小剂量甜菜根汁后，未观察到心血管指标有显著变化。
由于NO在固有免疫中起关键作用，未来需要开展研究以探索甜菜根和膳食硝酸盐提高FENO50及预防呼吸道感染的潜在临床效用。
