The Impact of Coffee on Sleep and Health (and How Much Should You Have?) | Dr. Matthew Walker

foreign you've changed your mind it seems on coffee in so much as you now advocate for it or at least support the idea of a cup of coffee in the morning and an outstanding question because we were going back and forth on what we should talk about in this conversation that I really don't know the answer to and that is why is coffee associated with so many of the same health benefits asleep it doesn't seem at least at face value to to make immediate sense so so both of those why a cup of coffee in the morning and why is it associated with some of the benefits of sleep and maybe you could also get into some of the pharmacokinetics of of caffeine or I mean I guess coffee could be its own thing just in terms of Half-Life and stuff so people have an idea yes so I've certainly changed my my tune on caffeine and I think just try to change my tune in general I think when I first came out with the book it was just getting my training wheels underneath me Public Communication I think I was probably a bit too absolutist in truth than anyone who speaks in absolute she should always be weary of and I was pretty much guilty of that and I think this that was true for caffeine and sleep in general but let me just come back to the first part of the question which is caffeine what is it how does it work in terms of waking you up how does it work in terms of preventing you from sleeping but also why I despite those things I would still advocate for it all right caffeine is a chemical as I'm sure you and everyone else knows it's a stimulants it's a psychoactive stimulant one of one of the few that we feel readily comfortable giving our children but caffeine Works in a very interesting way within the brain which brings us back to another chemical that sounds very similar called adenosine caffeine adenosine from the moment that you and I and everyone listening I suppose woke up this morning a chemical built up in your brain and that chemical is called adenosine and the more of it that builds up the sleepier that you feel and so we think of adenosine as a signal of sleep pressure it's not a mechanical pressure by the way it doesn't mean that the end at the end of the day your head is nearly going to explode on the basis of your adenosine it's just it's a chemical pressure caffeine Works to keep us awake by way of competing with adenosine so the longer that we're awake the more adenosine is building up and that adenosine is telling your brain okay you're getting sleepier and sleepier and after about 16 hours of being awake you should feel heavily weighed down by that adenosine signal that you can fall asleep easily and then you can stay asleep caffeine works by way of racing into the system and it latches on to those adenosine receptors but what it doesn't do is activate them because you would think well if it's binding on and latching onto those welcome sites of adenosine in the brain then wouldn't that make you more sleepy well the reason it doesn't is because it has the opposite effect well not quite the opposite effect it races in and it just latches itself onto those receptors and inactivates those receptors so it doesn't inhibit The receptors it just blocks them and so it's almost as though caffeine is like the mute button on your remote TV controller it just comes in and it mutes the signal of adenosine of of sleepiness so it's what we call a competitive receptor blocker and it has very sharp elbows it will come in and it will nudge adenosine out of the way latch on and hijack those receptors and block the signal of sleepiness and that's why all of a sudden you think well gosh I was feeling pretty sleepy I've been awake for 14 hours I have an espresso I don't feel sleepy anymore it's not as though you've removed the adenosine the adenosine is still present sleepiness is still present and it will continue to build up the longer that you're awake it's simply that your brain is no longer getting the message of adenosine because caffeine is blocking the signal if that makes some sense so that's the reason that caffeine will then start to disrupt your sleep and it will disrupt your sleep in probably several different ways the first is that it will because it's a stimulant prolong the time it takes you to fall asleep and you you mentioned that too the other aspect of caffeine though is that it's what we call anxiogenic that it increases your anxiety and anxiety including what we think of as physiological anxiety biological anxiety which is essentially having your fight or flight branch of the nervous system switched on into higher gear and aspects of your stress chemistry and things like cortisol those things will be ramped up by way of caffeine and that is the exact opposite of what you need to be able to fall asleep you need to disengage the fight or flight branch of the nervous system and shift over to the more restful branch of the nervous system that we call the parasympathetic nervous system and you can't do that because of the caffeine and so what happens is that psychologically the caffeine is preventing you from falling asleep then you start to get anxious because it's anxiogenic it increases anxiety at that point you start to ruminate this Rolodex of anxiety begins to whirl and you start to then ruminate and when you ruminate you catastrophize because everything seems so much worse in the darkness of night than it does in the light of day and at that point of catastrophizing and ruminating you're sort of dead in the water for the next two hours as it were stir in my life yeah I'm so sorry it's gonna sound pain for me familiar to many people out there so that's one of the issues with caffeine the other is its duration of action you mentioned it's pharmacokinetics it has a half-life of what we call five to six hours which is just a fancy way of saying that after about five to six hours half of the caffeine still in your system which means that caffeine has a quarter life of for the average adult at least 10 to 12 hours and I it's probably again not really a very good analogy but you know if you have a cup of coffee let's say at 1pm or 2 p.m in the afternoon is it similar to then saying well that's the equivalent of tucking myself into bed at midnight before I switch the light out I swing a quarter of a cup of coffee and I I hope for a good night of sleep it's probably not going to happen because a quarter of the caffeine is still in the brain swilling around at midnight so its duration of action is something that people may want to be mindful of and that will impact sleep the other component is that caffeine will destabilize your sleep so it makes your sleep more fragile and as a consequence if you are prone to waking up and we all will wake up across the night even healthy good sleepers will wake up because caffeine will destabilize and make your sleep more fragile it's more likely that you'll wake up and when you do wake up your sleep is less robust and it's harder for you to fall back asleep and so now sleep maintenance insomnia and then the final part of caffeine comes back to deep sleep if we and we've done these studies where we can dose people at different times of the day and into the evening and if you give people a standardized dose of caffeine maybe 150 180 or 200 milligrams which would be suppose the equivalent of probably a very strongly dripped brewed cup of coffee or probably one and a half cups of coffee what we can see is a decrease in the amount of Deep non-rem Sleep particularly in the first two hours of the night it can decimate that that deep sleep in fact there was a reduction if you look at that and we've done some of these Studies by a single cup of coffee in the evening it will drop the amount of deep sleep by about 30 percent 3-0 which to put that in context I would probably have to age you by about 12 to 14 years to get that type of reduction in your deep sleep or you could just do it every night with an espresso if you wanted to and I do think that that's relevant by the way some people will say look I can have a cup of coffee within or even two and I can fall asleep find a nice day of sleep so no harm no foul the problem there is that it discounts the idea that you have no sense of how much deep sleep that you get at night yes you probably remember did you struggle to fall asleep or did you wake up but none of us has a recollection of the quality of our deep slow brainwave activity but yet you may still be suffering from that excising of a significant amount of your deep sleep and so the next morning you don't feel refreshed or restored by your sleep but you don't remember struggling to fall asleep or having a hard time staying asleep and so you discount the idea that it was the coffee the next night but now you start reaching for three cups of coffee the next morning and then so on and so forth the sort of vicious cycle Begins the harder it is the next night to fall asleep the less deep sleep the more coffee you get and then people start falling into the Trap of alcohol or sleeping aids so so let me hop in let me hop in I'm gonna stage the intervention all right so so the cycle the stimulant depressant cycle is is a whole mess I've been a active participant on that field before but if I could just return to some of the questions that kicked us off so why why allow or endorse the idea of a cup of coffee in the morning number one right if if it is after this Litany of of sins and then how could coffee be associated with any of the health benefits of sleep and if so how is that the case you're absolutely right I think you know the time when I was writing the book a few years ago the evidence was starting to emerge there that drinking coffee had health benefits and there's been some great meta-analyzes quite recently and it is striking and you just can't really deny it on the strength of the evidence that drinking coffee is associated with numerous health benefits and the reduction in risk for numerous health conditions and what's striking as you mentioned elegantly is that many of the same health related conditions that drinking coffee is associated with reducing are the very same diseases that sleep will also reduce in terms of your risk so how on Earth does this work they seem completely paradoxical the answer is antioxidants because it turns out that the Coffee Bean itself contains much more than just caffeine it contains a very healthy dose of antioxidants a family called the polyphenols perhaps the principal one is well there's a number of different polyphenols that it contains but chlorogenic acids are probably the the principal kind that we think carry to an ester that carries some of these health benefits so what we realized is that the Coffee Bean because most people in developed nations are still deficient in their whole food dietary intake The Humble Coffee Bean has been asked to carry the Herculean weight of all of our antioxidant needs and that's why drinking coffee has is such a strong statistical Health signal in the data when you do epidemiological studies so it's not the caffeine that's related to the health benefits it's the antioxidants and case in point if you look at decaffeinated coffee you get many of the same I was just going to say I hate to spoil the party with a question if I could jump in for a second just a quick side note so the antioxidants and nutritional value of coffee being in let's just say less industrialized or lower income strata of various countries is true also for Coca in the Peruvian Andes and elsewhere it's actually a source of very important nutrition for for a lot of these communities and Indigenous groups so I just wanted to say that as an aside also chlorogenic acid I think is contained in other quite a few other compounds and and beverages if I'm not mistaken so I I want to say that it's present in yerba mate which they drink all the time in Argentina I may be getting that wrong so somebody can fact check me but is chlorogenic acid found in like Camellia sinensis tea plants or or other types of of beverages or is it particularly prevalent in coffee no you can find it it's certainly nowhere near exclusive to the Coffee Bean itself yeah by the way it doesn't have contain any chloride please don't be worried about it you're drinking in you know bleach or something like that it's got nothing to do with that but yet the chlorogenic acids that's certainly one group it's not to say it's the only group though there are others acromide is another one that we've been very interested in in terms of the Coffee Bean which is another antioxidant so it's a cluster of different antioxidants that provide these benefits any Brewing methods roasts grinds any combination of those variables that if one wanted to maximize for the good stuff and minimize the the the potential damage to sleep and sleep architecture any thoughts on on what that Goldilocks combination might look like it is interesting and by the way I think the Goldilocks combination comes on to the idea that you know when it comes to coffee it's the dose and the timing that make the poison here yeah that you know obviously if you look at the health benefits too once you get past about two and a half three cups of coffee a day the health benefits start to go down in the opposite direction so it's not a linear relationship don't start drinking like seven cups of coffee and be mindful of the timing but to come to your question I suppose if we're talking about caffeine concentration and then maybe antioxidant concentration actually here I am going to do a feature today I'm going to do a two by three because you can think about the rows of the this table being the caffeine and the antioxidants and then the columns three columns would be the roast maybe of the Coffee Bean the grind of the coffee being the granularity the coarseness and then maybe the Brewing method it's not quite as simple as this but certainly what we found is that for the roast of the Coffee Bean and this comes onto the color of the coffee bean a coffee bean is a coffee bean in terms of its when it comes out what changes its color is is how you roast it and what we found is that sort of gram for gram light roast actually has about the same caffeine content as dark roast but the issue is that the dark roast the longer that you roast it the more degraded The Coffee Bean becomes and hence the lighter its density so net net on average a lighter roast will contain more caffeine than a darker roast so it's a it's a little bit complex in terms of the grind I think it's fairly clear that fine grain coffee produces a higher degree of caffeine concentration than a coarse grain now of course we're not talking about Brewing methods yet but that's simply probably on the basis of surface area that the finer the grain the greater the surface area the greater the release of the caffeine Brewing method is it's really interesting if you look at some of the data the longer the Brewing method the greater the caffeine concentration relative to shorter also cold Brews tend to produce a stronger caffeine content than hot Brews I think part of that simply is down to the duration of the Brew itself cold Brews typically take longer and therefore you you get a stronger pound for the punch in terms of caffeine so that's caffeine antioxidants in terms of the chlorogenic acids you're you're probably going to favor lighter rather than darker roasts lighter roasts typically have higher amounts of chlorogenic acid than darker roasts although there is some evidence that dog roasts have higher amounts of some of the other antioxidants like acromide for example you don't need to worry too much in terms of the antioxidants and also by the way thankfully the decaffeinating process still preserves the antioxidants and that's why it's still related to the health benefits you don't lose out on the antioxidants when you switch to decaffeinated finer grains typically produce more antioxidants than also grind in terms of that and then Brewing method it's probably that cold brew seems to produce stronger antioxidant concentrations than probably the next down would be espresso preparation then instantly instant coffee seems to have finally higher concentrations of antioxidants than drip or sort of infusion bag versions so I'm sure that I'll stand corrected by the internet but that's sort of my reading perfect

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Id: pkfmKGEkl7Y

Length: 18min 34sec (1114 seconds)

Published: Fri Jan 20 2023