Caffeine

Here’s a practical overview of caffeine:

• Timing: If you use caffeine, have it early in the day. Delaying your first dose about 90–120 minutes after waking may help reduce an afternoon energy crash. Avoid caffeine within roughly 8–12 hours of bedtime, since it can disrupt sleep. 1 2
• Dose: Individual sensitivity varies. A starting range discussed is 1–3 mg per kg of body weight per sitting; check the caffeine content of your drink, since servings can vary widely. Higher intake may contribute to anxiety, jitters, headaches, and irritability. 3 4
• How it works: Caffeine blocks adenosine receptors, temporarily reducing feelings of sleepiness; it doesn’t remove the adenosine that builds up while you’re awake. When caffeine wears off, the accumulated sleepiness can become more noticeable. 5
• Benefits and tradeoffs: Caffeine can improve alertness, reaction time, memory retrieval, and physical performance, but regular users may mainly be returning to their usual functioning rather than gaining a lasting boost. It can also cause anxiety or interfere with sleep for some people. 6 7
• If you’re very sensitive: If even small amounts make you jittery or anxious, abstaining is reasonable; the discussion says there is no need to consume caffeine. 8

In short: use a modest amount early, and let your sleep and how you feel guide whether caffeine suits you.