Kennedy Michael D, Galloway Ashley V, Dickau Leanne J, Hudson Megan K
Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, E-488 Van Vliet Centre, Canada T6G 2H9.
Nutr Res. 2008 Sep;28(9):609-14. doi: 10.1016/j.nutres.2008.06.003.
Most North American workers drink coffee throughout their workday, although the cumulative effect of job stress and coffee is not well known. Research has shown that coffee affects the cardiovascular system and mental alertness primarily through the active ingredient caffeine; however, the dose of caffeine used in these studies is greater than a normal cup of coffee. In addition, these changes have been mostly determined in male caffeine-habituated consumers. Therefore, this study examined the effect of a normal cup of coffee on the cardiovascular and mental alertness response both before and after a mental stress task in 10 caffeine-naïve (23 +/- 5.0 years) and 10 caffeine-habituated (25 +/- 6 years) females. Blood pressure, heart rate, and mental alertness were taken at baseline (before coffee), 50 minutes after finishing coffee and immediately after a 9-minute mental stress task. The volume of coffee ingested for a 15-minute period was 350 mL (12 oz), which is equivalent to 140 mg of caffeine. The combined effect of coffee and mental stress significantly decreased diastolic blood pressure (Delta8 mm Hg) and increased heart rate (Delta6 beats per minute) and mental alertness (Delta67.3%) in caffeine-naïve and caffeine-habituated females, whereas systolic blood pressure (Delta10.3 mm Hg) only increased in the caffeine-naïve participants. Our results indicate that a normal cup of coffee can effect changes in blood pressure and mental alertness and that mental stress may alter the magnitude of change; however, the transient increase in systolic blood pressure after drinking coffee in caffeine-naïve participants requires further investigation.
大多数北美上班族在整个工作日都会喝咖啡，尽管工作压力和咖啡的累积影响尚不清楚。研究表明，咖啡主要通过活性成分咖啡因影响心血管系统和精神警觉性；然而，这些研究中使用的咖啡因剂量大于一杯普通咖啡中的含量。此外，这些变化大多是在有咖啡因成瘾习惯的男性消费者中确定的。因此，本研究调查了一杯普通咖啡对10名未饮用过咖啡因（23±5.0岁）和10名有咖啡因成瘾习惯（25±6岁）女性在精神应激任务前后心血管和精神警觉性反应的影响。在基线（喝咖啡前）、喝完咖啡50分钟后以及9分钟精神应激任务结束后立即测量血压、心率和精神警觉性。15分钟内摄入的咖啡量为350毫升（12盎司），相当于140毫克咖啡因。咖啡和精神应激的联合作用显著降低了未饮用过咖啡因和有咖啡因成瘾习惯女性的舒张压（下降8毫米汞柱），增加了心率（每分钟增加6次心跳）和精神警觉性（增加67.3%），而收缩压仅在未饮用过咖啡因的参与者中有所升高（升高10.3毫米汞柱）。我们的结果表明，一杯普通咖啡可以引起血压和精神警觉性的变化，并且精神应激可能会改变变化的幅度；然而，未饮用过咖啡因的参与者喝咖啡后收缩压的短暂升高需要进一步研究。
