Measuring caffeine consumption is harder than you think

Caffeine is a well-established performance enhancer; this is no secret, with many athletes using it to improve their performance. Non-athletes know this too, which is why almost 80% of the world’s population consume caffeine on a daily basis. As a result, caffeine is ubiquitous, and we are exposed to it in a number of different ways; primarily through hot drinks (such as tea or coffee), but also through foods (like dark chocolate) and medicines (many extra strength cold and flu or pain medicines contain caffeine).

» Related content: Craig Pickering has looked at several aspects of caffeine in sport, including individualizing pre-competition caffeine use, finding the right caffeine intake for performance, and habituation of caffeine use.

Recently, there has been an increased use of pre-workout supplements, both by the general gym-goer and performance athletes. Pre-workout supplements often contain a multitude of established performance enhancing substances—such as taurine, beta-alanine, and creatine—along with some less well-studied ingredients, like choline and gluconolactone. However, the most common ingredient in pre-workout supplements is caffeine. In part, this is because caffeine, as I’ve already mentioned, does reliably enhance performance. But it also has some very real, acute physiological effects, which supplement manufacturers like to use because it makes users feel like the supplement is effective.

But how much is the right dose? Some new recommendations have come out to help advise athletes, but even that can be difficult to implement due to the surprising difficulty of knowing how much caffeine is actually in what we consume. Below we take a look at how much caffeine we might consume, ideal dosing, and issues in quantification.

The effects of caffeine, habituation, and finding the right dose

Because caffeine is so widespread in our daily lives, many of us consume it on a regular basis, either deliberately—because of its performance or health enhancing effects—or “accidentally”, as an ingredient in something we like, such as soft drinks, or consume socially, such as coffee (although, of course, it’s not accidental that we like these substances, given caffeine’s somewhat addictive nature). Like most drugs, there is the potential that regular intake of caffeine means that we might build up a tolerance, and therefore require an increasing amount to get the same effect. This leads to us requiring more and more of it, just to feel the same; this can be problematic, because at higher doses caffeine can have some negative side effects, and, above intakes of around 9 mg/kg of bodyweight, there doesn’t appear to be any real advantage to consuming higher doses; as such, this represents a ceiling effect.

This process of becoming used to a drug is termed habituation, and it’s a topic I explored with John Kiely in our most recent paper, published in Sports Medicine and titled “What should we do about habitual caffeine use in athletes?” As a very brief summary, I believe that athletes need to consume around twice their habitual dose before a competition in order to maximize its performance benefit, so that if you regularly were to consume 3 mg/kg, pre-competition you’d need around 6 mg/kg. You can read my rationale for this in the paper, which is open access.

How much caffeine do you really consume?

But, there’s a problem to this process; you need to know how much caffeine you consume on a regular basis, and how much caffeine is in your pre-competition caffeine source (be that coffee, caffeine tablets, an energy drink, or pre-workout supplement). And, as it turns out, this is very, very hard to do. The work of Ben Desbrow, a world leading caffeine researcher at Griffith University, has illuminated this problem. For a 2007 study, his group analyzed the caffeine content of 97 espressos from commercial coffee companies. Their results indicated a wide range of caffeine concentrations; whilst the average was 106 mg, the range was 25 – 214 mg.

This means that, whilst you might think the caffeine content of your daily cup of coffee is consistent, it is highly variable depending on where you get your coffee from. In a later study, the same group examined the caffeine content in coffee bought from the same outlet, but at different times, again finding considerable variation; even if you buy your coffee from the same place every day, you’ll be getting different amounts of caffeine. Recently, in unpublished data, they reported significant variation in caffeine concentrations of Nespresso pods, both between flavors, but also within the same flavor at different times.

All of this means that it’s very difficult to accurately quantify your regular caffeine intake. In their most recent paper, Desbrow and colleagues cast their eye on the caffeine concentrations of pre-workout supplements. The first issue for consumers is that few of the pre-workout supplements listed the caffeine content on their label; many just state that it forms part of a proprietary blend. Again, as you might expect, they found large differences in caffeine concentrations between blends. They then purchased an additional two tubs of each pre-workout blend, and tested the caffeine concentrations. Here, they found that, for most brands, there were significant difference in the caffeine concentrations of each batch. As an example, Optimum Nutrition Gold Standard Pre-Workout, which I’ve used in the past, states on the label that it contains 1750 mg of caffeine per 100g (or 175 mg caffeine per serve). In their study, the researchers found that one tub contained 1859 mg, one 2053 mg, and the other 2247 mg.

How much of a problem is this? Well, it demonstrates the inaccuracies involved in accurately monitoring your caffeine intake. If you used Optimum Nutrition Gold Standard as your normal pre-workout supplement, you’d be expecting to get 175 mg per serving, but could be getting considerably more than this – up to 225 mg. If you’re big and heavy, this isn’t a problem, as caffeine is typically considered in mg/kg; for a 100kg person, this difference between servings is 0.5 mg/kg, which doesn’t sound like much. But for a 75kg athlete, this is 0.75mg/kg, which really is substantial. As an example, in my athletics career I settled on a pre-competition dose of 3 mg/kg, and I found that 3.5 mg/kg was too much. Had I been using this particular brand (and, to be clear, others are just as bad), I’d have been closer to 3.5 mg/kg than 3, which could have harmed my performance.

The troubles of quantification

All of this goes to show the issues in quantifying caffeine intake, which makes it hard to understand both your regular caffeine intake, but also your pre-competition and pre-training intakes. And this means that you likely never really know just how much you’re consuming. One solution could be to use caffeine tablets, either by buying them or making your own from powder, although there likely will be variability here too (perhaps Desbrow’s group will explore this next).

For now, it important to be aware that you cannot accurately predict your caffeine intakes, and so it’s important to build in a buffer to your calculations in order to guard against negative side effects. And, as we espouse in our paper, practice and refine your caffeine strategy in training before using it in competition.