Leah:

Hello and welcome to the Ideal Nutrition Podcast. This is episode 157 and today we are covering questions and misconceptions around caffeine. So this has been inspired by a recent research review that was titled Common Questions and Misconceptions About Caffeine Supplementation. So this is a peer review article from the International Society of Sports Nutrition.

They do really solid reviews like this occasionally where they cover a lot of common questions on certain topics. So we’ve basically chosen questions that they covered and then we’ve mixed it with a combo of the research. So we’re just going to discuss kind of the main points we found relevant for this episode and go through one by one.

Aidan:

The first one we’re covering is whether caffeine dehydrates you. So the logic is simply that caffeine is a diuretic. But an increase in urine production doesn’t necessarily mean that caffeine does dehydrate you. As a very simple example, if you consumed 200 ml of coffee and an increase in urine production by 20 ml, it’s technically a diuretic still, but that would be a net hydrating effect. But even the topic of caffeine being a diuretic is complex by itself. In people who consume caffeine infrequently, it clearly is a diuretic, like that’s a very common thing. But in those who consume it habitually,

Dosages up to around three milligrams per kilo appear not to have an effect in many cases. So that dosage is higher than a standard shot of coffee as well. Having a lot more caffeine than that amount can still have a diuretic effect even those who are consuming it, eventually acknowledging that obviously this is still individual, right? But if it is consumed alongside fluid, for example, in coffee, it’s almost always offset by the amount of fluid. Exceptions to this might be espresso shots with a small amount of fluid or if somebody was like using no-doz or something like that, tablets. But the short version is caffeine typically doesn’t dehydrate you.

Leah:

The second topic we’re going to cover is does caffeine decrease body weight and fat mass? So this review didn’t actually answer this question as well as we would have liked to give like a well -rounded opinion on it, but their findings were as follows. So in people who had not been consuming caffeine regularly, it seemed to help with weight loss a little bit when it was added in, as well as higher dosages were more linked with weight loss than lower dosages. I think we can all kind of understand why that may have been.

Number three, caffeine consistently increased fat oxidation during exercise, but we covered this in our last episode, oxidising fat as a fuel source does not necessarily equate to fat loss in the absence of a caloric deficit. So there’s that. And then number four, the results were inconsistent. So even though obviously that’s not like a primary finding, it’s still one we find relevant because it highlights that there were differences found in the research. And again, it highlights the flaws that are potentially there. They also mentioned that habituation to caffeine intake could reduce the impact on longer-term fat loss.

So for habitual consumers, it doesn’t really seem to be a factor. But if caffeine was to help with weight loss, so playing a little bit of devil’s advocate towards that direction, it would likely be due to three different factors. Suppressed appetite, increased total daily energy expenditure, and improved fat oxidation, which I did just briefly cover as to why that may not be the most appropriate or relevant argument to be making.

But our interpretation of these mechanisms are that the suppressed appetite thing, realistically, this is something that we do see in the short term for people who are starting to take on caffeine, but the more habitual consumers, it is unlikely to have any real impact. So if you’re a daily caffeine have a daily coffee drinker, potentially when you first started, it would have an appetite dwelling effect that was probably quite significant, but the more habitually you have it, the less of an impact this really is. But I’d have to say in my own practice, I definitely find that even habitual caffeine consumers can sometimes get this little bit of an appetite suppressing effect and that can help with like a fat loss phase as part of like general hunger management strategies, but not necessarily going to lead to weight loss in the absence of making other changes.

As far as the total daily energy expenditure increase goes, this is a thing that happens, but it is so, so small and probably pretty irrelevant. So is it really worth having a high dose of caffeine if you’re not going to be doing that for other reasons just to get this slight increase in energy output? Probably not. There’s probably quite a few negative side effects that are going to come along with that that make it not worth it.

And then like I said, the fat oxidation part is largely irrelevant because we know that burning does not equal fat loss in the absence of a deficit of calories. So overall in short-term studies, there is often a small favourable difference when it comes to caffeine and coffee consumption and weight loss, but it is highly unlikely to matter in the long-term.

Aidan:

Adding my two cents on the suppressed appetite thing. Something that shifted my view quite a few years ago is I’ve kind of come to the conclusion that anything that suppresses appetite outside of medication options probably doesn’t have that big of an impact long-term. And this is largely just because let’s say something does suppress your appetite a bit and that helps you create a calorie deficit. We know that the body responds to a calorie deficit by increasing appetite. That is just a standard response.

So it’s almost as if like, that becomes a new baseline after a while. My way of wording is that we probably, like tools like this probably have a lifespan of about 12-ish weeks before, and it probably has diminishing returns, right? And I’m like, is this less to do with the caffeine habituation and more to do that like just over time, if it does lead to a deficit, your body becomes hungrier, et cetera, etc.

And my kind of evidence for that is more along the lines of like, this actually explains a lot about how we see a lot of things that do suppress appetite in research not leading to significant weight loss in the long term. Caffeine is an example of this. Nicotine gum, I personally don’t have any interest in that, but we often see people lose a little bit of weight when they start doing that and then it just doesn’t matter over a six-month period. There’s other tools like that as well. The other example I’d use is if you got someone random off the street and you made them have 10 cups of herbal tea in a single day, they probably eat less calories that day, if you got them doing that for 20 weeks, do we think it would have the same impact?

And just from my personal experience working with people, there have been many people I’ve seen with quite high calorie intakes who have high intakes of those things as well. I do think these things balance out over time to a degree.

Aidan:

Do you see it also as a bit of a dimmer switch in that it may be at some points doesn’t necessarily decrease appetite super substantially, but still has like a minimal impact.

Aidan:

It plays a role. I do think so, yeah, for sure. Next one, does habitual caffeine consumption influence the performance response to acute caffeine supplementation? So we definitely feel a change in caffeine tolerance. That’s super common. Almost everybody will experience that. But whether that impacts performance is complex. The only way we can really know is obviously by measuring it, which fortunately that has been done in research.

It is a complex area and researchers had mixed findings. Like I’ve looked pretty hard to find an answer to this question. The findings are pretty mixed and my simple practical interpretation is simple, even though it’s a complex area. Either caffeine habituation doesn’t have an impact or it does. In the cases where it’s been concluded that it does, it seems like the simple solution is literally just going slightly higher than you normally do.

For example, if somebody is walking around having say four milligrams per kilo of caffeine per day, going up higher could solve that. Some of the researchers suggested like in this particular review actually, they suggested going as high as six to nine milligrams per kilo for situations like that. And I’m just talking numbers out there, so I’m just gonna say what that comes out as. If somebody is 80 kilos, the top end of that range, so nine milligrams per kilo is 720 milligrams. Once again, that’s just numbers, but that’s the equivalent of 4.5 or four and a half 500 ml cans of energy drinks. That’s high.

Leah:

That’s a lot of energy drinks. That would be a rare recommendation. That’s not something I would typically be doing. But if somebody’s daily intake was already super high, you could see why going slightly high and that isn’t actually that hot of a take to do. It’s not that big of a deal. So either it does or it doesn’t, but the simple solution is just going to look a bit higher.

Leah:

The next one is, does caffeine cause heart problems? So this is quite individual. So chronic usage is actually leaning in favour of, no, sorry. Chronic usage is actually leaning in favour of reduced issues. So we also see other evidence in research around coffee and longevity. I think an important thing to note there is like that’s not caffeine, that’s coffee, and there could be other compounds in coffee that could be helpful for longevity. Although if this was a huge issue, potentially we wouldn’t see that.

On the acute side of things, there can be a little bit more room for concern. In those who are not habitual consumers again, caffeine can increase heart rate and blood pressure pretty noticeably. It can also increase what is known as myocardial oxygen demand, which can be a trigger for cardiovascular events. This is why that individualised approach is relevant. It would be a stretch to say caffeine by itself in normal dosages causes long term heart problems.

But there is definitely room for some level of caution that is relevant in specific cases, particularly when there’s already underlying cardiovascular issues or things like really high blood pressure, particularly in those who are not habitual consumers of caffeine and then also in regards to dosages.

Aidan:

The next one is should pregnant women avoid caffeine? Leah and I prefer this stuff in advance and Leah chooses who says what section. I feel like she’s chucked me under the bus. Well, I never talk about pregnancy really or paediatrics. So you get this one. Yeah. So I’m just going to, I’m just going to stick straight to the research. Hey, like the only thing I want to say is that a lot of people talk about there being a cutoff of around 200 milligrams for caffeine while being pregnant. But then just jumping strictly to just what the research says. The actual consensus in the research is that the lower, the better.

Higher amounts of caffeine have always been linked with research, so going above that 200 milligrams, that’s been a long-term thing that everyone’s known for a long time. But even lower amounts, such as like 100 to 200 milligrams, are still linked with issues, such as increased risk of miscarriage, feotal growth restriction, low birth weight, as well as increased risk to offspring, such as cognitive development impairments.

For context, like a one shot of coffee could be like 80 milligrams of caffeine, but it’s pretty variable. Sometimes it will go above 100 milligrams, sometimes it’s significantly below. So those are the types of numbers we’re looking at. Based on the research, like the conclusion solely from looking at the data is that there is quote unquote, I’m just quoting the research at this stage. There’s no safe cutoff and caffeine should be minimised or avoided. I just want to discuss this topic with caution.

It’s a tricky topic, particularly when you factor in that stuff like tea or dark chocolate has small amounts of caffeine. If we came to the conclusion that there is no safe cutoff and caffeine should be minimised or avoided, then it’s like, how far do we go with that? Do we avoid dark chocolate? Do we avoid tea? Obviously, those are significantly below that 100 to 200 milligram kind of mark. The line has to be drawn somewhere. And based on the research, it seems lower than 200 milligrams. But right now, the consensus is simply just that the less, the better.

Leah:

And the final one we’re going to cover today is does waiting 90 minutes to two hours after waking to consume caffeine help you avoid that afternoon crash? We did actually previously do a whole episode on this and thank you to Aidan who put the number in there because I definitely couldn’t have remembered. But it’s episode 120 where we go into this quite deeply. We look through all the mechanisms and then come out with a conclusion.

But the quick version is that the impact on cortisol that is often proposed in this case is not really that relevant. Again, we keep going back to habitual consumers. So because this is really who this stuff is relevant to people that occasionally drink coffee or have caffeine. Probably don’t care about this much. It’s not an issue. But for habitual consumers, the impact of caffeine on morning cortisol is significantly blunted.

So it is much more relevant to people who consume it occasionally. But again, how much do those people care? Probably not. And then the adenosine blocking abilities of caffeine are also less relevant in the morning directly after waking, but that also doesn’t make it bad or a bad thing. There’s no specific evidence that caffeine within one to two hours of waking can actually cause that afternoon crash.

It’s also totally fine to have multiple doses of caffeine across the day to help offset this if you’re finding this is something that does happen. So assuming that you keep it to an appropriate total dosage of caffeine and it’s set up in a way that doesn’t impact your sleep, you can absolutely just time caffeine as you wake up and then caffeine when you expect that afternoon crash, if that’s something that is relevant to you. Honestly, if you want to delay your caffeine intake, also do it. It’s like, there’s just not much merit to it, but do what feels good for you realistically.

Aidan:

Yeah. This review is actually really savage on this topic, just being like, there’s no evidence that it causes a crash. And I was like, okay, let’s just go a little bit beyond that.

Leah:

Yeah. I think there’s just so much room for like, well, what feels good for you? What do you want to do? Do that. Like either way, it’s not going to make or break anything that you’re doing.

Aidan:

Yeah, for sure. Whenever I talk about caffeine, I always like to talk about the impact they can have on sleep and anxiety potentially and all these other things. But we really just wanted to keep this one simple and just focus on questions, misconceptions. Like everyone’s pretty on board with the fact they can impact sleep or I don’t know if you get this, but every time I post about this, I do get comments that like, I can have a coffee right before bed and I’m fine.

Leah:

All the time. People like, yeah, caffeine doesn’t impact my sleep. Well, there might be some impact on quality you just don’t notice.

Aidan:

Like you haven’t measured this.

Leah:

Yeah. When’s the last time you’ve not had caffeine? Like what, 10 years ago? You probably don’t know what it feels like.

Aidan:

But yeah, we’ll wrap up there. So this has been episode 157. As always, if you could please leave a rating and review. It means the absolute world to us and we are super grateful.