Caffeine is a natural stimulant found in various beverages and foods, such as coffee, tea, energy drinks, and chocolate. It works by blocking the action of adenosine, a neurotransmitter that promotes relaxation and sleepiness. By doing so, caffeine increases alertness and reduces fatigue. Caffeine also stimulates the release of adrenaline, which can temporarily increase heart rate and blood pressure. Moderate consumption of caffeine is generally considered safe for most people and may even have some health benefits, such as improved mental alertness and enhanced exercise performance. However, excessive intake can lead to side effects like jitteriness, insomnia, headaches, and increased heart rate.

“caffeine”的英语定义和含义

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