Influence of acute dietary nitrate supplementation timing on nitrate metabolism, central and peripheral blood pressure and exercise tolerance in young men,European Journal of Applied Physiology

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Influence of acute dietary nitrate supplementation timing on nitrate metabolism, central and peripheral blood pressure and exercise tolerance in young men
European Journal of Applied Physiology ( IF 2.8 ) Pub Date : 2023-12-02 , DOI: 10.1007/s00421-023-05369-z
Samantha N Rowland ₁ , Lewis J James ₁ , Emma O'Donnell ₁ , Stephen J Bailey _{1,

2}

Affiliation

Purpose

Dietary nitrate (NO₃⁻) supplementation can lower systolic blood pressure (SBP) and improve exercise performance. Salivary flow rate (SFR) and pH are key determinants of oral NO₃⁻ reduction and purported to peak in the afternoon. We tested the hypotheses that NO₃⁻-rich beetroot juice (BR) would increase plasma [nitrite] ([NO₂⁻]), lower SBP and improve exercise performance to a greater extent in the afternoon (AFT) compared to the morning (MORN) and evening (EVE).

Method

Twelve males completed six experimental visits in a repeated-measures, crossover design. NO₃⁻-depleted beetroot juice (PL) or BR (~ 13 mmol NO₃⁻) were ingested in the MORN, AFT and EVE. SFR and pH, salivary and plasma [NO₃⁻] and [NO₂⁻], brachial SBP and central SBP were measured pre and post supplementation. A severe-intensity exercise tolerance test was completed to determine cycling time to exhaustion (TTE).

Results

There were no between-condition differences in mean SFR or salivary pH. The elevation in plasma [NO₂⁻] after BR ingestion was not different between BR-MORN, BR-AFT and BR-EVE. Brachial SBP was unchanged following BR supplementation in all conditions. Central SBP was reduced in BR-MORN (− 3 ± 4 mmHg), BR-AFT (− 4 ± 3 mmHg), and BR-EVE (− 2 ± 3 mmHg), with no differences between timepoints. TTE was not different between BR and PL at any timepoint.

Conclusion

Acute BR supplementation was ineffective at improving TTE and brachial SBP and similarly effective at increasing plasma [NO₂⁻] and lowering central SBP across the day, which may have implications for informing NO₃⁻ supplementation strategies.

中文翻译：

急性膳食硝酸盐补充时机对青年男性硝酸盐代谢、中枢和外周血压及运动耐量的影响

目的

膳食硝酸盐（NO ₃ ^- ）补充剂可以降低收缩压（SBP）并提高运动表现。唾液流量 (SFR) 和 pH 值是口腔 NO ₃ ⁻减少的关键决定因素，据称在下午达到峰值。我们测试了以下假设：与上午相比，富含 NO ₃ ^{− 的}甜菜根汁 (BR) 会在下午 (AFT) 增加血浆 [亚硝酸盐] ([NO ₂ ⁻ ])、降低 SBP 并更大程度地提高运动表现（AFT）早上）和晚上（EVE）。

方法

十二名男性通过重复测量、交叉设计完成了六次实验访问。 MORN、AFT 和 EVE 摄入了 NO ₃ ⁻贫化甜菜根汁 (PL) 或 BR（约 13 mmol NO ₃ ⁻ ）。在补充前和补充后测量SFR和pH、唾液和血浆[NO ₃ ^- ]和[NO ₂ ^- ]、肱动脉SBP和中枢SBP。完成高强度运动耐量测试以确定骑行至力竭时间（TTE）。

结果

平均 SFR 或唾液 pH 值在不同条件下没有差异。 BR摄入后血浆[NO ₂ ^- ]的升高在BR-MORN、BR-AFT和BR-EVE之间没有差异。在所有情况下补充 BR 后，肱动脉 SBP 均未发生变化。 BR-MORN (− 3 ± 4 mmHg)、BR-AFT (− 4 ± 3 mmHg) 和 BR-EVE (− 2 ± 3 mmHg) 的中心收缩压降低，时间点之间没有差异。在任何时间点，BR 和 PL 之间的 TTE 均无差异。