Torwen:
My name is Torwen Eerkens and I’m here with my co-host Aidan Muir. And we have done previous episodes on caffeine on this podcast before. Including caffeine for performance, caffeine and sleep. We have also covered general caffeine questions and misconceptions. Today, we’re doing a quick seven things worth knowing about caffeine.
Aidan:
So we’re going to start with caffeine sources and the content of those things. Starting off with coffee, I would typically call a standard shot of coffee around 80 milligrams. We know that this can be hugely variable. I like to put that out there for context. It gives context for everything else that we go through from here.
Energy drinks. In Australia, typically a 500 mL energy drink is around 160 milligrams of caffeine. That’s the standard. Most are around that range. Obviously, a 250 mL one would be around 80.
Pre-workout often ranges from 240 to 300 milligrams of caffeine. There are also many scenarios where it’s higher or lower than that. Another one is NoDoz as well. If somebody wants tablets or capsules, those are 100 milligrams of caffeine.
Torwen:
Soft drinks. A standard can of Coke is about 34 milligrams. Then of course, we look at tea. Black tea is about 40 to 50 milligrams per cup. Green tea is a little bit lower, at around 20 milligrams per cup.
Interestingly, other foods can also contain a bit of caffeine. Dark chocolate, small but real, has about 20 to 60 milligrams per 100 grams. Then, of course, we have supplements. Things like energy gels will typically contain around 100 milligrams of caffeine.
Aidan:
Yeah, some are quite low. Some are super low.
The next one is the half-life of caffeine. This is typically around three to five hours. That can vary hugely between people based on genetics and other factors.
Torwen:
What that means is, if you drink a 200 milligram coffee at around 2 pm, you will still have caffeine circulating. You will still have around 100 milligrams in your system three to five hours later.
Genetic variability is an interesting one when it comes specifically to caffeine. Some people can have a double espresso after dinner and feel completely fine. They sleep fine. Others will be more wired from having caffeine in the afternoon. This largely comes down to genetics.
The primary enzyme responsible for metabolising caffeine is in the liver, CYP1A2. Is that how you would pronounce it, Aidan?
Aidan:
I was going to say C-Y-P-1A2. But yeah, I don’t know. I’ve only read it. I haven’t heard anyone actually say it.
Torwen:
No, nor have I. Genetic variants in this enzyme mean some people are fast metabolisers who clear caffeine quite quickly. Others are slow metabolisers who keep caffeine in their system for much longer.
Another gene that we look at is ADORA2A. It influences how sensitive your adenosine receptors are to caffeine. This means some people feel less dramatic effects. Others will have an anxiety response.
Aidan:
You can test for this in Australia. My understanding is you can do it for around $100 through direct-to-consumer tests. Often, they will test a bunch of other genes alongside this. But this is one of the most clear-cut. It is what it is. You test the genes and get the results. It’s very clear. This is an accurate way of testing it.
But it’s also up to you whether it’s worth testing. You could just use your best judgement. I think there are a lot of people who believe they’re quicker metabolisers. They might not necessarily be. But I think many people, particularly if they believe they’re more sensitive, are probably right. There’s a lot to go with that. It’s up to you whether it’s worth testing.
Torwen:
So, the mechanism. How does caffeine actually work?
When you’re awake, your brain accumulates a molecule called adenosine. It’s a natural byproduct of cellular activity. What it does is bind to receptors in the brain. It progressively signals fatigue. The longer you’re awake, the more adenosine builds up. The sleepier you feel.
Now, caffeine works by blocking adenosine receptors. It doesn’t actually give you energy. It simply prevents adenosine from delivering that fatigue signal. This results in increased alertness and reduced perception of effort. It also reduces fatigue and improves focus.
Aidan:
The next one is training. We’re going to talk about what I’ll call two different dosages here.
One to three milligrams per kilogram of caffeine can help with making you feel more alert. It can make things feel easier. We call this reducing the rate of perceived effort. In some cases, that can indirectly improve performance.
But higher dosages, like three to six milligrams per kilogram, can directly improve performance. Particularly at the top end, so five to six milligrams per kilogram.
The mechanisms related to that are complex, varied and debated a little bit. Some include central nervous system changes. These allow more motor unit recruitment and stronger muscle contractions. There are also potential changes in fat versus carbohydrate utilisation.
As I said, some of those are subject to debate. Whether they matter is debated. Whether they cause this improvement is debated. But the performance improvement is still consistent.
Torwen:
Specifically for training, timing does matter. Peak caffeine levels in the blood normally occur around 30 to 60 minutes after ingestion. Dosing at the right time before exercise makes sense. This is particularly relevant if you’re taking a higher dose for training purposes.
Aidan:
And one reason I mentioned the gels is that some have lower amounts of caffeine. That’s more just for a top-up. You do the numbers on three to six milligrams per kilogram. Then you’re like, why would a really low-dose gel help with this? But research still finds low doses can help. During longer bouts of endurance activity, they can still improve performance too.
Torwen:
For sure. Sleep. Most people do understand that caffeine directly before bed is not the best idea.
Gardener et al. did a 2023 meta-analysis. They specifically examined the effect of caffeine on subsequent sleep. It found that caffeine consumption significantly reduced total sleep time and sleep efficiency. It also increased the time it takes to fall asleep. The effects were more pronounced the closer you had caffeine to bedtime. Overall, caffeine reduced total sleep time by about 45 minutes. It also reduced sleep efficiency by 7%, which is a fair amount.
Aidan:
Yeah, absolutely. It’s huge. Then the last thing we’ll talk through is anxiety. Specifically, the impact caffeine has on it.
We know that caffeine can upregulate anxiety if it’s already present. It can worsen symptoms. L-theanine, which we’re going to talk about very briefly, can sometimes offset some of the upregulation from caffeine. It doesn’t blunt the effects. But it can reduce an elevated heart rate. It can reduce jitteriness and help with focus.
There’s a lot of research on this. From the caffeine perspective, an anecdote I’ll tell is from many years ago. I used to work almost exclusively with veterans. Almost all of them had PTSD and anxiety as part of that. Many were also on medication for anxiety.
Many people had been on medication for 10 to 20 years. Many of those people were also having five cups of coffee a day. And in some cases, definitely not all, going down to zero cups of coffee meant medication was no longer needed.
There are so many factors in that. There are so many multifactorial aspects. It had been 20 years since they had been on the medications. Were they as needed now as they were at the start? Was this masked a little bit by the caffeine? Was it because they’d never tried coming off the medication? Was this the first thing that prompted it?
There are so many things that go on with that. There are also many cases where significantly reducing caffeine wouldn’t have made much difference. But it is something that I think is worth trialling. If not completely cutting down to zero, reducing is worth trying as well.
And another thing I would chuck in there is that going from a high amount of caffeine to zero is grim. It is a grim process in many cases. Something I heard on a podcast once was so simple, but worth tracking. They mentioned that if you’re going to do it, have some Panadol. The headache is the worst symptom if you were to do that.
So I would definitely add Panadol if you’re just doing that. Another way is cutting down very slowly. But some people would prefer to do it all in one go. It’s up to you if you go down that route.
Torwen:
I think, because it’s so highly individual, it’s worth doing some testing to see where your tolerance is. If you notice you’re getting more anxious and jittery, your dose of caffeine might be too high. If your heart is racing too much, your dose might also be too high. So just reduce it and see how you feel instead.
Aidan:
Incredible. Well, we will wrap up. This has been episode 262 of the Ideal Nutrition Podcast. As always, if you haven’t already, please leave a rating and review. That would be massively appreciated.