Caffeine Half-Life Calculator | Hacker News Reader

Caffeine Half-Life Calculator

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82 pointsKomoD42 comments

Genetic differences can alter caffeine metabolism significantly, reducing half-life by up to 80% (which has a huge impact since it’s typically 5-6 half-lives to “flush” a drug out of your system).

Basically it may take some individuals 48 hours to metabolize all caffeine while others may do it in 10 hours.

https://jamanetwork.com/journals/jamanetworkopen/fullarticle...

I'm in this camp and it sucks. If I have a full size cup of coffee at 5am, my sleep will suffer. Otherwise fit, healthy dude in my 40s, but have the caffeine tolerance of a toddler.

Working out seems to also affect this. The days I workout I can "tolerate" more than when not.

same. a hard workout beats me up and gets me sleeping like a baby.

i'd imagine the blood pumping, sweat, lots of water intake, and boost to metabolism probably doesn't hurt either.

I've actually been cutting out caffeine after listening to Michael Pollan talk about drugs and society on NPR.

Turns out the half life is typically long enough that using caffeine every day long term will lead to cognitive decline because of sleep deprivation. It's good for an occasional boost, but you're really burning the candle at both ends.

Yes, this calculator doesn't show how you end up a week later when your base level isn't zero. Taking a 2 day break from coffee can help a lot.

Yeah, I have no caffeine on weekends and that just seemed like a good idea to me without any evidence.

I'm off caffeine after many years of daily consumption. Took a few weeks, but my energy level is now about the same as it was before I quit and I no longer feel tired without it. I do quite miss the taste and ritual of tea and coffee, though.

I stopped caffeine for 2 years and never felt the same. Happy for you.

This one?

https://www.npr.org/2020/03/25/821402773/michael-pollan-on-t...

That looks like it, but I heard it in 2022 or 2023, might have been a re-run.

I can't listen to it right now, but I remember in the program he was talking about publishing some of his books describing his experiences with illegal substances and he had his publisher agree to pay all potential legal costs on top of paying his regular salary to his wife in case of incarceration.

I don’t get it. If you only consume caffeine in the morning, every morning, how does it affect your sleep? By bedtime it is all metabolized.

> By bedtime it is all metabolized.

According to Pollan, for most people, there's still enough in your system to disrupt your natural sleep; your brain doesn't shut down enough to get a good rest. IIRC, he was discussing monitoring brain activity during sleep and you can see the difference between people who drank coffee that morning, and people who didn't. Caffeine has just about left your system completely around the time you wake up and start drinking it again, which usually isn't too long before you start getting caffeine withdrawal symptoms.

edit: half life for caffeine is 2-12[1] hours (most sources claim ~5), depending on the person. For a half life of 6 hours (using this because it's close to 5 and divides evenly into 24), you still have >1/8 of what you drank that morning in your system when you go to bed, and 1/16 when you wake up. Over the course of a lifetime, it's not hard to imagine that having a cumulative effect.

1: https://www.sleepfoundation.org/nutrition/how-long-does-it-t...

What is good rest? I get 80 minutes or more a night of deep sleep regardless of my morning caffeine intake. I almost always wake up well rested and still drink ~300mg of caffeine over the course of a day.

I didn't read the book, but from his interviews it sounds like all he did was gather N=1 over sufficient time to show it effects him. This is one case where I am going to have to appeal to authority. I have yet to see evidence your morning coffee is destroying your cognitive function. I have not experienced it either. Given my data is just as valid as his I would like to see actual controlled studies on this. In particular on the absolutely outlandish claim that 1/8th to 1/16th of the dose of caffeine remaining in your body does anything if you're consuming it only in the mornings.

I'm not a sleep researcher, so I'm not really qualified to say. I did poke around and find some papers on caffeine's affects on sleep, but there honestly wasn't (IMO) a huge amount a research, and what I did find mostly focused on caffeine intake less than 6 or 8 hours before sleep. Everything I found did see differences in brain activity or REM, but there seems to be room for interpretation on what those differences actually mean (turns out brains are really complicated).

I did find this though:

"Regular Caffeine Intake Delays REM Sleep Promotion and Attenuates Sleep Quality in Healthy Men"

>Our data indicate that besides acute intake, also regular daytime caffeine intake affects REM sleep regulation in men, such that it delays circadian REM sleep promotion when compared with placebo.

https://pubmed.ncbi.nlm.nih.gov/34024173/

Based purely off of my layman's intuition, changing how you sleep is not optimal for brain health, it disrupts a natural and very important process.

I thought Matt Walker did a lot of research on caffeine + sleep. He runs the sleep lab at UC Berkeley and published "Why We Sleep".

80% of adults have caffeine intake in a given day. So what's more plausible, that 80% of adults have cognitive decline, or the author in question is full of crap?

given the state of society, why do you think everyone is thinking well?

Given the word "cognitive" was used I assume "cognitive decline" refers to some sort of scientific measurement like an IQ test. If 80% of the population is experiencing it that would be pretty easy to measure, I would think?

If we are just discussing whether human beings are awful... humans were being awful far before the popularization of coffee beans, so that seems like a red herring in general.

I stop caffeine intake around noon, and was just disillusioned about it being out of my system by bed time nine hours later.

I'm the same, 1pm is an absolute cut off otherwise it'll be a restless night

I build tolerance to caffeine very quickly for some reason. One night I drank two redbulls so I could finish a project (I had been drinking a lot of coffee and energy drinks during that period) and decided to take a quick nap before going into crunch mode and ended up sleeping the entire night.

I had a redbull yesterday at 17:30 and fell asleep with no problem at 22:30.

If I want the true effects of the energy drinks I have to use them sparingly or else my tolerance ramps up and it doesn’t give me the energy buzz but kinda makes me sleepy...

Caffeine affects sleep quality as well as the ability to fall asleep. So just falling asleep doesn't mean you aren't suffering any negative effects.

Yes, I can sleep even with very high amounts but my sleep quality is horrific. Although sleeping through the night you wake up like you didn't sleep at all.

If anyone's not sure what values to input, it looks like the values provided (67mg and 130mg) are for roughly one 40-50ml serving of espresso followed by 2x that (a double espresso).

I usually have one espresso (or lungo) after breakfast and another after lunch. So this means that this extra shot at ~13:00 means I have over 2.4x the caffeine in my system at 22:00 than if I'd only had the morning coffee (3.6mg vs 8.83mg). Not sure whether I expected any different since twice the coffee works out to roughly twice the caffeine (since I go to bed a little later) :-)

A lot of people don’t realize that caffeine is not the only substance that affects our body when we drink coffee.

There is also paraxanthine, which is a metabolite of caffeine that has a similar half-life and similar effects.

Paraxanthine can increase lipolysis, which means it breaks down fat and releases fatty acids into the bloodstream. It can also enhance alertness, mood, and cognitive performance.

So, even when the caffeine levels in your blood start to drop, the paraxanthine levels are still high and keep you stimulated. That’s why the effects of coffee can last much longer than you think.

I used to be a hardcore caffeine aficionado. I learned that if I took it after lunch, my sleep would be impacted, not noticeably on one day but the effect stacks since it's a daily habit and that long term rejuvenation is worse. Eventually my father listened to some podcast and became opinionated about artificial caffeine and didn't want me to drink energy drinks.

I wonder what different effects tea has? I saw a study once that the boost you feel from coffee is only getting you to where you'd be if you never drank it. It's an illusory stimulation where you're just erasing withdrawal symptoms.

Actual stimulation is much more limited than the half life of the substance would suggest, as it is with most other stimulant drugs.

Even if much of the substance remains unchanged by the liver the stimulation effect is front loaded. After a short time, typically 2-3 hours, physiological stimulation decreases rapidly unless even more stimulant is added.

> "Keep in mind that after the amount becomes very small, it is likely that the body will dispose of it all at once rather than halving the amount forever."

I don't think that's how it works...

Also useful in case you have a pile of polonium-207 lying around.

The graph ends at 22:00, but I go to sleep at around 2:00. :(

Maybe it was just changes but it appears to end at 10:00 am the next day

Smokers have shorter caffeine half-life (wish I knew that when I was quitting smoking) while birth control drugs or liver problems can extend it.

https://sci-hub.se/10.1002/cpt197824140

> Mean caffeine t1/2 in smokers (3.5 hr) was shorter than that in the nonsmokers (6.0 hr).

small study but that's pretty cool

How does this apply to decaf (which is still a non zero amont of coffee, but certainly reduced to actual product)?

How quickly is caffeine absorbed? The chart shows the entire dose taking effect instantly.

Apparently 99% of it is absorbed within 45 minutes [1].

—-

[1]: https://www.ncbi.nlm.nih.gov/books/NBK223808/

Given studies associating positive health outcomes with 2-4 cups a day (no idea what defines a cup), would the implied extrapolation here be that a small amount of caffeine during sleep is helpful (holistically)?

My own assumption is that it's _very_ helpful (for the coffee or other industries that commission or promote such information).

There are plenty of studies showing X is good for your health (in moderation, of course!), usually all funded by companies selling X.

Got milk?

Look up “coffee flavinoids”. There are plenty of health podcasters promoting coffee and green tea consumption who are independent (Rhonda Patrick, Andrew Huberman, Peter Attis)

By the way, decaf coffee appears to have the same flavonoid content as caffeinated.

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