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  • Kelly Johnston, FNTP, RWP

Caffeine Fail

Updated: Aug 24, 2018


Oops. I meant to tell the barista to make it decaf. Hmmm. Well…it’s only 3:30. I should be fine. I’ll just have half of it.


Famous last words, and I knew better.


A momentary indulgence on a cool, stormy afternoon. Yes, I said cool. Unheard of in a south Texas summer, and such a rarity that I actually felt like I needed warming up. We were making our usual Trader Joe’s/Whole Foods run before heading home from Austin, and something warm and smooth sounded perfect for the ride home. We were there celebrating our youngest son’s birthday with family over the weekend. It had been a great success. He’d requested his Uncle Dusty’s Famous Korean Ribs for dinner, and they did not disappoint. Lots of laughter, hugs, and games punctuated our time together, but now it was time to leave. That steamy, creamy cup of coffee would ease the transition as we navigated the wet highway and watched the lightening, listened to music, and I disappeared into a book.


That was when I realized I’d neglected to specify “decaf” and decided to throw caution to the wind.


Bad. Idea.


At least this is what I thought as I lay in bed willing myself to doze off in my stimulated state. So strange, I thought to myself. I don’t feel at all buzzed after my morning cup of coffee with breakfast, but if I deviate and have another later in the day (remembering now why I so rarely do this), sleep is not going to be my friend.

I surrendered to the energy and got up to read. No sense in lying there getting more annoyed by the minute, right? Might as well make some more headway in that book.

At least I can get closer to the next one in my waiting-to-be-read stack.


Two hours later I give it another go, and this time, mercifully, I am able to drift off.


Knowing the lack of sleep dealt a blow to my immune system and interfered with the normal humming along of my hunger hormones, but feeling not too much worse for the wear, I was still thinking about the conundrum that is caffeine the next day. What IS the half-life of a caffeine hit, anyway? How long is it that the stuff is merrily coursing through my veins, wiring me for a night of unwanted alertness? Why is it some people can have a cup of coffee at bedtime and pass out the moment their heads hit the pillow and others (uh…me) will be counting sheep til nearly dawn? It’s not fair!



This was my mindset as I sat down to look into it. What I found answered most of my questions.


A cup of coffee contains roughly 200 mg of caffeine, and has a half-life of 5 to 6 hours. This means that after 5 or 6 hours, half the caffeine started with still remains in the blood stream. So, if I’m average, then half of my 3:30 pm cup of joe’s caffeine is still hanging around in my system at 8:30 or 9:30. Apparently, that’s enough to make sleep just a dream for me a couple hours later.


Proponents of health have had a love-hate relationship with coffee and caffeine for decades. Whether it is good or bad for us depends on the research findings of the time. It’s been altogether hazardous for our health, raising the risks of bladder cancer, heart attack, and hypertension, but it’s also been declared preventive for prostate, liver, skin, and a type of uterine lining cancer. A recent meta-analysis of over 100 observational studies and randomized controlled trials showed an association between coffee consumption and a probable decrease in cancers of many kinds, cardiovascular disease, Parkinson’s disease, and type II diabetes, while also showing an association with an increase in high blood pressure and cholesterol. But why is there so much seemingly conflicting evidence about the merits and risks of drinking coffee?

It seems that the answer to this question may be as individual as whether or not coffee disturbs our sleep.


Caffeine is metabolized by an enzyme called CYP1A2, which is controlled by a gene which is also conveniently called CYP1A2. This gene determines how quickly we break down the caffeine in our bodies. One variant of this gene causes the liver to metabolize caffeine quickly – so if a person inherits two copies of this variant (one from each parent), then he is a fast metabolizer and clears caffeine from his body rather quickly. Inheriting one or both of the slow variants means that caffeine takes four times longer to clear from the body than it does in a fast metabolizer. Studies looking at coffee’s association with heart attack first showed that consuming four or more cups per day raised the risk of such events by 36%. But when researchers split the group into categories based on how fast their bodies cleared caffeine, they found that it was only the slow metabolizers whose risk increased. They found the same thing when they studied coffee’s effect on hypertension. Blood pressure risk did in fact increase, but not amongst the fast metabolizers.


Does this mean we should all run out and get our genes tested so we know whether coffee helps or hurts us? I think not. For one thing, other studies have shown that there are actually multiple genetic factors that play into our caffeine metabolism. And besides, if we listen to our bodies, we will have the answer. If we can drink a cup of coffee before bed and still fall asleep with no trouble, then we know, right, that we’ve cleared the caffeine quickly. And those of us who are twiddling our thumbs waiting for elusive sleep to finally come after a cup of coffee in the midafternoon, well, our bodies are telling us that we are still experiencing caffeine’s effect late into the night.


I’m Kelly, and I’m a slow metabolizer of caffeine. I don’t need a genetic test to tell me that. What does this mean for me? That one cup of coffee in the early day is enough for me. That more than that too late in the day will disrupt my sleep. And I can take from this other clues into the way caffeine may effect my body in the long term. Overdoing caffeine may be harmful to my cardiovascular health.


And what about you folks blessed with caffeine metabolism of the fast kind? Yeah, I’m a bit jealous of you. But consider that coffee is a stimulant that can make life harder on our adrenal glands if it is overdone, and consider that it has diuretic properties that mean we should increase our water intake for every cup of coffee we drink in order to function at our hydrated best. So even if you are able to drink coffee all day and right up to bedtime with no ill effect on your sleep, it doesn’t mean that you should. Our bodies are truly asking for water, no matter what our tasters and smellers are clamoring for. This is how I placate my coffee-loving heart when I’m around fast metabolizers. No, it really doesn’t help much, but it pays me back at bedtime for sure.

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