Department of Kinesiology, School of Health and Human Sciences, Indiana University Purdue University Indianapolis.
Department of Internal Medicine, School of Medicine, Indiana University Purdue University Indianapolis.
J Gerontol A Biol Sci Med Sci. 2021 Mar 31;76(4):591-598. doi: 10.1093/gerona/glaa311.
We have recently demonstrated that dietary nitrate, a source of nitric oxide (NO) via the nitrate → nitrite → NO enterosalivary pathway, can improve muscle contractility in healthy older men and women. Nitrate ingestion has also been shown to reduce blood pressure in some, but not all, studies of older individuals. However, the optimal dose for eliciting these beneficial effects is unknown. A pilot randomized, double-blind, placebo-controlled crossover study was therefore performed to determine the effects of ingesting 3.3 mL/kg of concentrated beetroot juice containing 0, 200, or 400 µmol/kg of nitrate in 9 healthy older subjects (mean age 70 ± 1 years). Maximal knee extensor power (Pmax) and speed (Vmax) were measured ~2.5 hours after nitrate ingestion using isokinetic dynamometry. Blood pressure was monitored periodically throughout each study. Pmax (in W/kg) was higher (p < .05) after the lower dose (3.9 ± 0.4) compared to the placebo (3.7 ± 0.4) or higher dose (3.7 ± 0.4). Vmax (in rad/s) also tended to be higher (p = .08) after the lower dose (11.9 ± 0.7) compared to the placebo (10.8 ± 0.8) or higher dose (11.2 ± 0.8). Eight out of 9 subjects achieved a higher Pmax and Vmax after the lower versus the higher dose. These dose-related changes in muscle contractility generally paralleled changes in breath NO levels. No significant changes were found in systolic, diastolic, or mean arterial blood pressure. A lower dose of nitrate increases muscle speed and power in healthy older individuals, but these improvements are lost at a higher dose. Blood pressure, on the other hand, is not reduced even with a higher dose.
我们最近的研究表明，膳食硝酸盐（通过硝酸盐→亚硝酸盐→NO 肠唾液途径产生的一氧化氮（NO）的来源）可以改善健康老年人的肌肉收缩力。在一些但不是所有的老年人研究中，硝酸盐的摄入也已被证明可以降低血压。因此，进行了一项随机、双盲、安慰剂对照交叉研究，以确定在 9 名健康老年人中摄入 3.3 毫升/公斤的浓缩甜菜根汁（含有 0、200 或 400µmol/kg 的硝酸盐）的效果，这些受试者的平均年龄为 70 ± 1 岁。使用等速测力法在硝酸盐摄入后约 2.5 小时测量最大膝关节伸肌功率（Pmax）和速度（Vmax）。在每个研究期间定期监测血压。与安慰剂（3.7 ± 0.4）或更高剂量（3.7 ± 0.4）相比，较低剂量（3.9 ± 0.4）后的 Pmax（以 W/kg 计）更高（p <.05）。Vmax（以 rad/s 计）也倾向于在较低剂量（11.9 ± 0.7）后更高（p =.08）与安慰剂（10.8 ± 0.8）或更高剂量（11.2 ± 0.8）相比。9 名受试者中有 8 名在较低剂量时的 Pmax 和 Vmax 高于较高剂量时。这些与剂量相关的肌肉收缩力变化通常与呼吸 NO 水平的变化平行。收缩压、舒张压或平均动脉血压没有明显变化。较低剂量的硝酸盐可提高健康老年人的肌肉速度和力量，但在较高剂量时这些改善会消失。另一方面，即使使用较高剂量，血压也不会降低。
