7 New studies you MUST know about Caffeine

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00:00 Introduction

00:27 Cognition

03:39 Sleep

05:56 Placebo

09:11 Lack of dose-response

11:55 Tolerance – 3 studies

17:26 Conclusion


Caffeine is the most popular drug on the planet. In this video, I’m going to share the results of seven new studies of what caffeine does to your mind and body. By the end of this video, you will accept that everything I’ve told you is true, but you will reject all of it and you will be left with an overwhelming sense of dread and cognitive dissonance resulting in you disliking this video. The first study investigators What caffeine does to your working memory performance. Many people intuitively have the idea that caffeine just makes everything better and makes you smarter and makes you more. However, that’s not true.

Caffeine selectively enhances some aspects of your cognition, how your brain functions, but it deteriorates others. In this study, they extended the findings of short term research to longer term effects. For ten days, they had people take either a placebo three times per day or caffeine 150 milligrams. So that’s 450 milligrams per day, which is a substantial amount. It’s about five cups of coffee for the average guy. And another group also consumed the caffeine. But at the 10th day, they went into withdrawal. They didn’t consume any caffeine, so they compared placebo versus caffeine versus withdrawal. They found that in contrast to short term studies, which find that a single dose of caffeine often improves or does not affect working memory performance. In the longer term, caffeine actually led to reduced working memory performance. They found higher error rates, longer reaction times compared to the placebo condition in the caffeine group. They also found reduced activity in the hippocampus, which is a vital area in the brain that is involved in learning and memory formation. The researchers concluded – Our data suggest that daily moderate dose caffeine intake leads to a compromised working memory function, which may remain reduced during accurately withdrawing from daily intake. These findings suggest that there are certain adaptations in the brain with long term usage of caffeine that change the response to caffeine compared to when you just take a single serving and you are not yet habituated to the higher dose that you are using chronically. This scenario is very similar to what most people do with caffeine. It’s that they consume multiple cups of coffee throughout the day. And this study would suggest that if you do this, you actually suffer from impaired working memory performance. This study reminds me of earlier research on this topic, which looks at the effect of various drugs, including caffeine on chess performance. And they found that while a single serving at least improved attention and it also made them make better moves with the stimulants, including caffeine. But it actually didn’t improve overall chess performance because they also took much longer for each move and therefore lost more games on time. So the overall performance with caffeine and without caffeine was similar.

I found that many things seem to get better with caffeine because you feel better, you have more energy. But when you objectively measure your productivity and your performance, a lot of tasks actually don’t improve with caffeine. Caffeine is mainly effective for very simple task where you otherwise have trouble keeping your attention. Now, I wouldn’t be too freaked out about this study. It’s not the case that they lost 20 IQ points or something, and it is only a single study so far. But it is good to be aware that caffeine use does not simply make you smarter. If you take caffeine before an IQ test, for example. And in the research on chess performance, for example, you generally find that there is no objective improvement. What caffeine does is it selectively enhances some aspects of how your brain functions while deteriorating others. And based on this study, the cost benefit deteriorates with chronic, relatively high daily usage. The second new study is a meta analysis that looked at the effect of caffeine consumption on sleep. It’s generally well known that caffeine is bad for your sleep, but the magnitude of this effect is generally under appreciated. Caffeine deteriorates pretty much every aspect of your sleep and for a much longer time than most people realize. The researchers concluded: to avoid reductions in total sleep time and sleep quality coffee should be consumed at least 8.8 hours prior to bedtime, and a standard serving of pre-workout supplement should be consumed at least 13.2 hours prior to bedtime. They found that on average in the literature, caffeine impaired sleep quality and quantity to what they called a clinically significant degree. Every individual aspect of sleep quality did not deteriorate that much. But when you add it all together and you look at the effects that that reduction in sleep time and quality has on objective tasks, it is actually quite notable. So caffeine made it harder to fall asleep. It reduced sleep efficiency and it reduced the time spent in deep sleep stages while increasing the time in light sleep stages. It also increased the time that people spent awake at night, even if they didn’t remember it afterwards. So overall, caffeine is definitely no bueno for your sleep, and it seems that even a standard single serving of coffee needs to be consumed 9 hours prior to bedtime for the average individual. or as a pre-workout supplement, which typically has about 200 milligrams of caffeine, needs to be consumed a full 13 hours prior to bedtime, which means that you would not be able to train more than, say, 12 hours before bedtime if you don’t want any negative effect on your sleep.

Now, these effects are very individual and you might not have problems falling asleep with caffeine use closer to bedtime, in that case – Great. However, you should be aware that your subjective sleep quality is not necessarily the same as your objective sleep quality, so you might not feel the effects anymore, but there can still be objective effects. In fact, in one of the studies, they found that a single double espresso consumed in the morning still objectively impaired sleep quality at night. So that’s a single double espresso consumed and that still reduced sleep quality at night, even though subjectively nobody feels anything anymore from their caffeine use that long after consumption. The third study shows that most people derive a significant placebo effect from using caffeine, even if they haven’t consumed any caffeine. Let me clarify. The researchers had people consume three different supplements, none of which actually contained anything, they were all placebos. But even though they were all inert capsules containing a placebo, meaning nothing, the people were told that they did contain something. In one condition they were told contains cellulose, which is an inert substance. It’s controlled condition. So it’s a true placebo where people know it’s a placebo. In the other condition, people were told it contains caffeine, which is the true placebo condition, where people consume a placebo, but they think it’s caffeine. And then well, we’ll see what happens. And the other condition, they were told that they consumed lactic acid. And the idea is that many people believe that lactic acid is bad for your muscles. So in the workouts that they were going to perform afterwards, this should have a negative effect. This is actually a myth. Your muscles barely produce any lactic acid and they mainly produce lactate, which is actually a base. And lactate is not responsible for muscle fatigue. It actually buffers against fatigue. That’s simply a complete outdated myth. After consuming the three placebos with different expectation effects, they consumed a workout. Now you can see here what the results are.

Basically, we see very strongly what people call the placebo effect and the nocebo effect. The placebo effect is that positive expectations can manifest into actually positive objective outcomes. So they thought they were consuming caffeine and therefore they actually performed better. Interestingly, not only did they perform better, they performed more repetitions. They also had a lower rating of perceived exertion. So it’s not the case that they simply worked harder and therefore got better performance. No, they actually felt like they were working less hard, but they objectively got better results. But it’s a very strong placebo effect. And then in a nocebo condition where they consumed fake lactic acid, you saw this was not statistically significant, but the trend is clear and it aligns with a lot of other research. You saw a reduction in the number of repetitions they could perform while increasing the rating of perceived exertion. So we also see a discrepancy here between how people feel the workout is and their objective performance where they don’t go hand-in-hand so they can actually move in the opposite directions. So the mental effect is even stronger than the physical effect. And this, I think, is a very good illustration of the placebo and the nocebo effect, the positive and the negative expectation effects. And this builds on previous research showing that caffeine use has more mental placebo effect, more psychological effect than objective physical effect. In fact, there are some previous research in which this kind of placebo effect is stronger than the objective actual physical effects of the caffeine. So people that think they are consuming caffeine, they derive a greater performance enhancement during workouts, for example, than people that actually consume caffeine. But we’re told it’s a placebo. So the mental, thought that you’re consuming caffeine in many ways is more important than the actual physical effect of the caffeine.

That’s how strong the placebo effect of the caffeine is. And this primarily mental psychological effect of caffeine is also illustrated well by the next new study that I would like to share. And it shows that caffeine does not have a dose response effect. So what they did is they had well-trained collegiate sprinters and jumpers perform jumping type workouts with different dosages of caffeine. And they found that there were no significant differences between the different doses of caffeine in jumping performance, 1, 3, and 6 mg per kg dosages were all equally effective. And this is absolutely crazy if you think about it, because there is almost no drug that does not have a dose response effect. Dose response effect means that dose determines the response. So higher dosages result in higher responses. almost every drug you take has this. You take more of the drug, you get more of an effect. Caffeine does not have this effect. It’s now been replicated in multiple studies. This study just reaffirms that again. And the difference is, is massive. We’re not talking about small differences in dosages. This is one mg per kilogram, which for the average guy would be like a Red Bull, which is maybe 80 milligrams or something. And if you’re a very big guy, it would be like one cup of coffee for most women it would be like half, half a cup of coffee or a weak cup of coffee, 3 mg per kg, three times that and six is six times that. So that would be like six red Bulls for the average guy. And even for a small female, it would be three Red Bulls. So it’s a crazy difference in caffeine intake. And as long as people don’t know the difference in caffeine intake, that part’s crucial. They actually don’t respond very differently.

Now, again, this certainly varies per individual, because I remember one time I slept over at one of my friend’s houses and then we went to the cinema the next day and I was walking up the stairs and my hands were shaking, I was sweating and I literally felt like I was going to faint. I was becoming so lightheaded, I thought I was going to fall down the stairs. And I was thinking, What? What happened? What? What? Why do I feel this way? Because I wasn’t ill or anything. And then I suddenly remembered, oh I had my friend’s morning cup of coffee and he was a massive caffeine addict. So his morning cup of coffee was like the equivalent of probably eight normal cups of coffee, which came close to hospitalizing me. So clearly, if you go up dosage to a certain level, then you will notice that something is wrong. You will get side effects, but within certain limits. For most individuals, you can have quite big differences in caffeine dosage. And as long as you’re not aware of that, it actually doesn’t affect your performance and it certainly doesn’t affect your objective physical performance in a gym, for example, or doing things like IQ tests. The last three new studies of what caffeine does to your mind and body looked at the effects of caffeine, habituation. So becoming used to caffeine, regularly consuming caffeine, and how this affects what effect you can still get from caffeine. The first study found that soccer players that were habituated to consuming an average of 360 milligrams caffeine per day. So that’s like three, three and a half cups of coffee no longer derived any positive ergogenic effect in their workouts from 100 or 200 milligrams. And again, there were no differences between the dosages reaffirming a lack of dose response. With one exception, the 200 milligram dosage improved at least one out of the six test measures, which is probably something we can ignore. But it might suggest that a higher dosage was still somewhat effective in this case because they were habituated and compared to a placebo, they needed a higher dosage than otherwise to still get at least some positive effects. But overall, the study found basically no effect anymore of moderate dosages of caffeine, like 1 to 2 cups of coffee or a small to a big energy drink on their workout performance.

The next study again looked at the effect of pre-workout caffeine consumption in people that were habituated to caffeine use, this time in strength trained men. And the researchers concluded the oral intake of three milligrams per kg of caffeine by resistance trained men habituated to caffeine, and they were habituated to an average of 2.2 mg per kg per day, which is actually not much at all, did not enhance the number of repetitions during a medium load full body resistance training session to failure. So they basically concluded that even when you’re used to relatively benign intakes of caffeine, even for a big guy, that would only be two cups of coffee. They no longer got any positive effects for their workouts of a much higher dosage, even of three milligrams per kg, which is like three Red Bulls for the average guy. overall, disappointing findings for people that use caffeine regularly in terms of how much benefit they can still expect to get from their pre workouts. The third study further reaffirmed this. They found that recreational cyclists no longer derive any benefit from caffeine before their workouts unless they abstain from caffeine at least 24 hours before, 8 hours earlier, they still had at least 1.5 mg per kilogram of caffeine, which is like their regular one or two cups of coffee for most people they’d have that in the morning and then later they have a workout in a day and then even six milligram per kg caffeine. So a massive dosage of caffeine no longer objectively improved their cycling performance.

The researchers concluded: these data indicate that pre exercise caffeine only improves recreational cycling performance when compared to bouts preceded by caffeine abstinence, suggesting that habitual users may not benefit from six mg per kg caffeine and that previous work may have overstated the value of caffeine supplementation for habitual users. So if you’re using caffeine regularly throughout the day and then you still want to benefit from it later for your workouts, you’re probably not getting a whole lot of effect anymore. I would note that these are new studies from this year on this topic, but there are also a lot of other studies that still find some benefits, in fact, or including even some meta analyzes. This seems to vary per individual, and the research is a lot less compelling when you look at If you look at people over time, the same individuals consuming caffeine than you typically see that the effect wanes. The researchers, weaker research, which is cross-sectional and looks at different types of people, used a different dosage of caffeine, does still find effects. However, that’s A weaker research. And B, what they often do is they look at the effect of, say, three or six milligrams per kg caffeine. So very high dosages of caffeine like multiple energy drinks worth of caffeine. And then they still find an effect in people that are used to consuming lower dosages because most people, when they consume coffee, for example, that’s like one mg per kilogram of caffeine or a little bit more for most people. So it’s they’re used to the equivalent of one cup of coffee. And then the research just shows, well, if you consume three cups of coffee, you still get a response. Of course, that doesn’t mean that much because the response might be reduced and it might be that you need a higher dosage now. So research on this is not unanimous.

It’s not the case that all research finds that you get zero effects like these new studies find – just absolutely zero effect from even high dosage of caffeine. If you were used to even just moderate caffeine consumption, you might still get an effect. But I would say if you simply anecdotally think about how much you feel the effect of caffeine, I think it’s very hard to argue that there is no tolerance taking place. If you take no caffeine for, say, ten days. Research finds that it takes about nine days to fully re-sensitize your receptors. So that’s the good news. The only good news in this video, 4 to 9 days, you can completely re sensitize your receptors depending on how much caffeine you used before. If you do that and then you consume, say, two red bulls or energy drinks in general, you will have a significant effect. Some people are extremely caffeine insensitive. Maybe they don’t feel it, but the average individual will feel a significant effect from two monsters or red bull’s or whatever. Now, keep drinking those two energy drinks every single day for two months. Can you honestly say you still feel the same amount of effect?

At some point, most people feel very little. In fact, some people are so addicted to caffeine that they can consume caffeine before going to bed and they sleep just fine, or at least they don’t notice they don’t sleep as well anymore. I would certainly be very skeptical of the study’s finding no habituation to caffeine mentally. It’s very clear that there is a habituation in these new studies which suggest that the habituation effect is actually very strong and basically completely negates any benefits you get from caffeine consumption. If we take all of these things together, what does this mean for caffeine use? Well, it’s actually very clear. Caffeine is a popular drug. And what do people do with drugs? They typically abuse them. That’s why most drugs get banned in society, because the societal harm is too great. The only thing called the short term effects. And they don’t consider the long term effects like withdrawal and tolerance habituation. And they just use it whenever they want to feel better. And especially with sleep, that often leads to a self-reinforcing negative spiral where they rely on caffeine to feel normal. They sleep worse, they typically need more caffeine after that to again, feel normal. And you get into the spiral of increasing caffeine usage in an increasingly poor sleep.

More caffeine usage, worse sleep, more caffeine until at some point you’re consuming caffeine just to feel normal and you are no longer deriving any objective benefits compared to if you just have never consumed any caffeine and your sleep was better and now you just rely on the caffeine to make you feel normal so there’s no increase anymore above baseline of your caffeine usage. In that scenario, the prudent thing to do is to go cold turkey and go off all caffeine or at least taper down your dosage. If you don’t want to go cold turkey, then for after 4 to 9 days, reestablish a prudent, rational dosage regimen of caffeine use, which is typically about one cup of coffee or one energy drink per day, especially if you want to use it for your workouts. You don’t want to use caffeine before to workout already earlier in the day because that will probably negates much of the benefit you get during your workouts. It’s also perfectly fine if you don’t want to use any caffeine at all, because most of the effect of caffeine is mental, psychological. It’s not really objective. If you are naturally motivated for your workouts, then caffeine really doesn’t do much. And most long term studies find that it doesn’t announce muscle growth or fat loss or strength development or anything. So it’s also perfectly fine not to consume any caffeine. But if you do want positive benefits, then it is better to moderate your dosage and stick to a low dosage. Because if you just logically put it together, we know that the research – low dosages like one milligram per kilogram, are equally effective as higher dosages, higher dosages result in worse sleep quality, and may also impair working memory function and some other aspects of cognition. And much of the effect is mental anyway. So if you combine those things together, it logically makes sense that you consume low dosages of caffeine, typically one energy drink or basically the minimum you need to feel good.

If you are not tolerant to caffeine and you stick to that low amount of caffeine, you can still drink decaf coffee, decaf tea, herbal teas, those kind of things, if you like that. But to remain very sensitive to caffeine, you need to limit your total daily or weekly intake to roughly 700 milligrams per week or one milligram per kilogram per day. That’s a dose that you can sustain long term without significant habituation and you can reap the full benefits thereof without incurring any withdrawal symptoms if you don’t take it. So you don’t become reliant on it and it actually elevates your mood performance. Everything above baseline rather than just taking you out of withdrawal. Now, the response to caffeine use is very individual and there are a lot of other factors at play, but I hope you can use these findings to use caffeine more optimally in your life and make it suit your lifestyle.

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About the author

Menno Henselmans

Formerly a business consultant, I've traded my company car to follow my passion in strength training. I'm now an online physique coach, scientist and international public speaker with the mission to help serious trainees master their physique.

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