If general coffee lovers feel sleepy in the morning after staying up late, they will choose to drink coffee to supplement a large amount of caffeine or nap to refresh themselves, but this will not be friendly to some special groups of people. For example, someone with a caffeine intolerance who has a nap and lunch habit may feel sleepy after lunch, but morning coffee may interfere with napping and anxiety.

1. Because the caffeine in coffee and the feeling of drowsiness after eating can affect people's mental state.

  After drinking coffee the effects of caffeine typically reach peak levels in the blood within an hour and can last up to six hours， so caffeine interferes with your sleep when you nap.
  After eating, especially if you are very full, the food will increase the activity of the gastrointestinal system and excite the parasympathetic nerves, resulting in relatively more blood supply to the gastrointestinal tract and a relatively reduced blood supply to the head, leading to drowsiness and fatigue, appear relatively sleepy phenomenon.
  Food can also increase the secretion of insulin, reduce protein breakdown, and stimulate the body to produce melatonin, making people drowsy and sleepy.
  Under the combined effects of caffeine and lack of sleep, you'll be jittery and anxious in the afternoon.

2. How to use coffee and nap to combat sleepiness?

  This suggestion is more suitable for those who are intolerant to caffeine and have naps habit and lunches habit.
Method: coffee nap > coffee or nap
  2.1. Choose to drink a small amount of coffee or decaf coffee in the morning according to your sleepiness and preference， a small amount of caffeine to suppress your morning drowsiness and not affect your nap, skip this if you're not sleepy in the morning and don't want coffee.
  2.2. Drink a small amount of coffee or decaf coffee before a nap, usually at lunchtime.
  2.3. After finding a comfortable place to take a nap for 15-20 minutes, you will reduce sleepiness.

3.How coffee naps work？

Coffee naps work by combining the waking effects of caffeine with the restorative aspects of napping.

3.1.  Waking effects of caffeine:
  Caffeine is a stimulant that can make you energized and alert. Because people's sleepiness is related to adenosine in the body, the amount of adenosine usually increases when awake and decreases during sleep. Adenosine binds to special receptors in the brain to slow down brain activity and prepare for sleep. But caffeine reduces adenosine in the body, so the brain will become excited.

3.2. Restorative aspects of napping:
  Appropriate naps can increase alertness and heightened mental sharpness. Researchers have found that naps can reduce adenosine levels in the body and relieve drowsiness. The ideal nap time is about 20 minutes, and naps longer than 30 minutes can lead to deep sleep and may lead to sleep inertia.

4. Are Coffee Naps Effective?

While there have only been a few studies on this subject with small sample sizes, they all point to the fact that coffee naps are effective.

4.1. Experimen： Previous research has shown that caffeine and a < 15-min nap effectively and separately reduce sleepiness in drivers for 1 hr.

4.2. Experimen： Whether the combination of a short daytime nap with caffeine, bright light, and face washing was effective against mid-afternoon sleepiness.
  Results: Caffeine+Nap was the most effective for subjective sleepiness and performance level; its effects lasted for 1 h after napping. Nap+Bright-light was comparable with Caffeine+Nap, except for performance level. Nap+Face-washing showed mild and transient effects, however, it suppressed subjective sleepiness immediately after napping.

 
This article is for informational purposes and should not replace advice from your doctor or another medical professional.