Dear Science,

My husband drinks a couple of mugs of coffee with breakfast. He drinks an energy drink at lunch. In the afternoon, he has a soda. He does this every single weekday. Is he going to explode?


A Concerned Spouse

Science gave up caffeine just before starting his intern year—no coffee, no soda, no tea. The withdrawal was awful—headaches, sweats, fatigue, and a level of lethargy that even 80-hour workweeks and 30-hour continuous shifts could not generate. Aside from giving me some scant credibility with my clinic patients ("Dear sir, please do give up the cocaine. I gave up coffee! It can be done!"), I'm not sure of the wisdom of this move.

Nobody really knows how caffeine works. Sure, sure, caffeine inhibits adenosine receptors. But the effects of adenosine are poorly understood; thus, we really don't know how caffeine does the things it does to the brain and body. In contrast to caffeine, cocaine and methamphetamine work via a rather destructive method, knifing the haunches of increasingly pitiful neurons in the brain to release their goodies. Caffeine seems the gentler stimulant.

This question—is drinking caffeine good for you or bad for you?—is the sort that gives Science conniptions. The studies are notoriously difficult to perform—attempting to randomize people to drinking or not drinking caffeine over a lifetime, just to measure the effect? Not going to happen. So what we're left with is a whole bunch of observational studies in humans and a few randomized controlled trials in animals.

Let's start with the animal studies. Probably the most infamous is a study done on spiders by Dr. David Noever at the Marshall Space Flight Center. Dr. Noever was attempting to find good model organisms for studying the effects of drugs. Making a spiderweb takes a lot of planning and effort, and it's easy to see when things go awry. The high-on-pot webs were beautiful until the spiders became lazy and stopped partway through. Caffeine created completely haphazard webs, with neither organization nor function. Search for the images of the spiderwebs; the effect is pretty impressive.

Moving on to people, most studies have shown a slight health benefit from mild to moderate caffeine consumption—with decreased rates of liver (and more surprisingly) heart disease. Reasonable caffeine consumption is associated with modest decreases in rates of cancer overall. How much is reasonable? No more than four eight-ounce cups of coffee a day (or the equivalent). It's hard to say caffeine causes these effects; perhaps caffeine consumers are doing something that changes these risks.

So far as we can tell, caffeine is probably safe, and maybe even a bit helpful to health, if consumed moderately. In contrast, energy drinks—containing stimulants beyond caffeine—aren't. A few young people a year get a stroke from too much stimulant-containing energy drink.

Stimulatingly yours,


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