Department of Health and Exercise Science, Wake Forest University, Winston-Salem, North Carolina 27109-7868, USA.
Nutr Res. 2012 Mar;32(3):160-8. doi: 10.1016/j.nutres.2012.02.002.
Little is known about the effect of dietary nitrate on the nitrate/nitrite/nitric oxide cycle in older adults. We examined the effect of a 3-day control diet vs high-nitrate diet, with and without a high-nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics and blood pressure using a randomized 4-period crossover controlled design. We hypothesized that the high-nitrate diet would show higher levels of plasma nitrate/nitrite and lower blood pressure compared with the control diet, which would be potentiated by the supplement. Participants were 8 normotensive older men and women (5 female, 3 male, 72.5 ± 4.7 years old) with no overt disease or medications that affect nitric oxide metabolism. Plasma nitrate and nitrite levels and blood pressure were measured before and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet + supplement (P < .001 and P = .017 for nitrate and nitrite, respectively) and high-nitrate diet + supplement (P = .001 and P = .002), but not for control diet (P = .713 and P = .741) or high-nitrate diet (P = .852 and P = .500). Blood pressure decreased from the morning baseline measure to the three 2-hour postmeal follow-up time points for all treatments, but there was no main effect for treatment. In healthy older adults, a high-nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction.
关于饮食硝酸盐对老年人硝酸盐/亚硝酸盐/一氧化氮循环的影响知之甚少。我们使用随机 4 期交叉对照设计，检查了 3 天对照饮食与高硝酸盐饮食（含或不含高硝酸盐补充剂（甜菜根汁））对血浆硝酸盐和亚硝酸盐动力学及血压的影响。我们假设高硝酸盐饮食与对照饮食相比会显示更高水平的血浆硝酸盐/亚硝酸盐和更低的血压，而补充剂会增强这种作用。参与者为 8 名血压正常的老年男女（5 名女性，3 名男性，72.5 ± 4.7 岁），无明显疾病或影响一氧化氮代谢的药物。在每餐前后和每餐后 3 小时每小时测量血浆硝酸盐和亚硝酸盐水平以及血压。与对照饮食 + 补充剂（硝酸盐和亚硝酸盐分别为 P <.001 和 P =.017）和高硝酸盐饮食 + 补充剂（P =.001 和 P =.002）相比，血浆硝酸盐和亚硝酸盐的平均日变化与基线相比差异有统计学意义，但与对照饮食（P =.713 和 P =.741）或高硝酸盐饮食（P =.852 和 P =.500）相比差异无统计学意义。所有治疗组的血压均从早晨基线测量值下降到 3 个 2 小时餐后随访时间点，但治疗组无主要影响。在健康的老年人中，早餐时摄入高硝酸盐补充剂可使血浆硝酸盐和亚硝酸盐水平全天升高。这一观察结果可能对血管功能障碍的老年人在进行体力活动时摄入硝酸盐补充剂的时间安排具有实际应用价值。
