My daily caffeine intake consists of one regular-sized cup of instant coffee (with milk and sugar) in the morning and one regular-sized cup of black tea (with milk and sugar) in the late afternoon. This would not normally be seen as a sign of caffeine addiction except that on the days that, for whatever reason, I cannot get my morning cup of coffee (in the case that I have spent the night at some place where I cannot get one first thing), I feel a little unsettled and will often go to some lengths to find a coffee shop where I can get a cup.
Food writer Michael Pollan says that that feeling first thing in the morning is indeed a sign of caffeine addiction, that my vague need to drink a cup of coffee is because the caffeine withdrawal symptoms are kicking in and I need to suppress them.
The scientists have spelled out, and I had duly noted, the predictable symptoms of caffeine withdrawal: headache, fatigue, lethargy, difficulty concentrating, decreased motivation, irritability, intense distress, loss of confidence and dysphoria.
According to the researchers I’d interviewed, the process of withdrawal had actually begun overnight, while I was sleeping, during the “trough” in the graph of caffeine’s diurnal effects. The day’s first cup of tea or coffee acquires most of its power – its joy! – not so much from its euphoric and stimulating properties than from the fact that it is suppressing the emerging symptoms of withdrawal. This is part of the insidiousness of caffeine. Its mode of action, or “pharmacodynamics”, mesh so perfectly with the rhythms of the human body that the morning cup of coffee arrives just in time to head off the looming mental distress set in motion by yesterday’s cup of coffee. Daily, caffeine proposes itself as the optimal solution to the problem caffeine creates.
He says that researchers have pinpointed some benefits of caffeine when taken in moderation.
I found numerous studies conducted over the years reporting that caffeine improves performance on a range of cognitive measures – of memory, focus, alertness, vigilance, attention and learning.
The current scientific consensus is more than reassuring – in fact, the research suggests that coffee and tea, far from being deleterious to our health, may offer some important benefits, as long as they aren’t consumed to excess. Regular coffee consumption is associated with a decreased risk of several cancers (including breast, prostate, colorectal and endometrial), cardiovascular disease, type 2 diabetes, Parkinson’s disease, dementia and possibly depression and suicide. (Though high doses can produce nervousness and anxiety, and rates of suicide climb among those who drink eight or more cups a day.)
But, as always, there are downsides, and that is the negative impact that caffeine has on sleep.
An English neuroscientist on the faculty at University of California, Berkeley, Walker, author of Why We Sleep, is single-minded in his mission: to alert the world to an invisible public-health crisis, which is that we are not getting nearly enough sleep, the sleep we are getting is of poor quality, and a principal culprit in this crime against body and mind is caffeine. Caffeine itself might not be bad for you, but the sleep it’s stealing from you may have a price. According to Walker, research suggests that insufficient sleep may be a key factor in the development of Alzheimer’s disease, arteriosclerosis, stroke, heart failure, depression, anxiety, suicide and obesity. “The shorter you sleep,” he bluntly concludes, “the shorter your lifespan.”
Walker explained that, for most people, the “quarter life” of caffeine is usually about 12 hours, meaning that 25% of the caffeine in a cup of coffee consumed at noon is still circulating in your brain when you go to bed at midnight. That could well be enough to completely wreck your deep sleep.
I thought of myself as a pretty good sleeper before I met Walker. At lunch he probed me about my sleep habits. I told him I usually get a solid seven hours, fall asleep easily, dream most nights.
“How many times a night do you wake up?” he asked. I’m up three or four times a night (usually to pee), but I almost always fall right back to sleep.
He nodded gravely. “That’s really not good, all those interruptions. Sleep quality is just as important as sleep quantity.” The interruptions were undermining the amount of “deep” or “slow wave” sleep I was getting, something above and beyond the REM sleep I had always thought was the measure of a good night’s rest. But it seems that deep sleep is just as important to our health, and the amount we get tends to decline with age.
Pollan says that all the sleep researchers he spoke to did not take any caffeine.
I myself will likely continue my current practices. As for sleep, I tend to get about nine hours per night, usually getting up just once and falling asleep again fairly easily. I do dream a lot. How much of my sleep is deep sleep and how much is REM sleep, I have no idea. Apparently the iWatch can tell you but I not going to spring for hundreds of dollars for yet another device just to get that information.
Pollan’s article has in interesting extended section on the history of coffee and tea and about the political role that coffee houses played in England, serving as a kind of library and salon for intellectual discussions.