My personal trainer was the first to suggest I might be dependent on caffeine. Four cups of coffee a day did not sound excessive to me, but I decided to look into it. Caffeine turns up in many products. These are approximate amounts per serving:
- Filtered coffee: 85 mg
- Instant coffee: 60 mg
- Espresso: 65 mg
- Decaf coffee: 3 mg
- Tea: 30 mg
- Cola: 18 mg
- Iced tea: 16 mg
- Energy drink: 80 mg
- Pure chocolate: 14 mg
- Milk chocolate: 6 mg
- Some painkillers: 100 mg
- Some diet pills: 100 mg
Yes, even decaf coffee contains a little caffeine.
I had read that people who consume more than about 100 mg a day may develop a dependence. That is only a little more than one typical cup of coffee, though individual responses vary.
For many people, a morning coffee is a ritual and a way to feel more alert. Caffeine can help because it blocks the effects of adenosine, a chemical involved in building sleep pressure while you are awake. As the day goes on, that pressure rises and you feel sleepier. It falls again while you sleep.
Caffeine blocks receptors for adenosine, making you feel less sleepy. That is useful sometimes, but it can also mask your need for rest.
I would rather get enough sleep than rely on caffeine to push through tiredness. It can also disrupt sleep, because caffeine has a half-life of 5 to 7 hours. A strong cup can therefore still have an effect many hours after you drink it.
A coffee at 7:30 p.m. may leave a substantial amount of caffeine in your system at midnight. That can make it harder to fall asleep or sleep deeply.
The kick may fade after an hour or two, but the caffeine itself can linger much longer.
I stopped consuming caffeine to see whether I would notice any symptoms. I did: headaches, fatigue, low energy, and a low mood. After about ten days, the worst of it had passed.
I then limited myself to three or four cups of good coffee a week, usually when I work in cafés. I no longer drink it every day.
Now each cup tastes better to me, and I notice its effects more. I feel more energetic and creative, less anxious, and I sleep better—perhaps partly because I drink coffee only in the morning.
My own rule is to keep caffeine below about 100 mg on the days I have it, no more than three days a week, and only in the morning.
Of course, I wrote this while enjoying a hot café latte and a slice of chocolate birthday cake. How awkward.