The sports supplement market is big business, but the reality is that most of these supplements have little evidence for a benefit. It is not all negative news though as there is a small group of supplements that are backed by science and which can play a performance-enhancing role in some athletes. In this series on sports supplements, I will profile this group of supplements and for this podcast, the spotlight is on caffeine. 

Caffeine is a popular go-to supplement for many athletes. And for good reason. Not only is it the key component of one of the world’s most widely used legal drugs – I’m talking about coffee here people – it is also a sports supplement that is well supported by scientific evidence that it can offer a performance-enhancing benefit in some athletes by providing a small, but worthwhile, enhancement of performance over a range of exercise situations from short-duration events right through to endurance events.

In fact, caffeine was one of the few supplements to get the tick for having good evidence behind it in the 2018 IOC Consensus Statement on dietary supplements for use by high-performance athletes and I’ll link to this document in the show notes https://bjsm.bmj.com/content/52/7/439

So, let’s go over a summary of those benefits. Caffeine use has been seen to improve endurance capacity such as exercise time to fatigue and endurance-based time-trial activities of varying duration. And this endurance benefit is seen across cycling, running, rowing and many other sports.

To put some numbers to those benefits, caffeine consumed during endurance exercise may enhance a cycling time-trial performance by between 3% and 7%. During short-term, maximal effort and repeated sprint tasks, caffeine taken around an hour before exercise results in performance gains of 3 percent for task completion time, mean power output and peak power output during anaerobic activities of 1–2 min in duration. While for repeat sprint performances during intermittent team game activities. a one to eight percentage improvement is typically seen.

So, how does caffeine work its magic? Caffeine is a stimulant that elicits many physiological and psychological effects in the body. While its mechanism of benefit is not fully understood, caffeine may enhance alertness and reduce the perception of fatigue and improved vigilance and alertness and change in the perception of work effort during exercise. It can also increase motor unit recruitment and muscle contractility making the whole musculoskeletal system work more efficiently. There are also neurotransmitter effects and increases in endorphin release which can increase feelings of wellness, and give you the exercise "high" that people often experience after working out

Caffeine may also stimulate fatty acid release during endurance activity and spare the use of glycogen, but these effects are not universal and likely not important in overall performance benefits.

Caffeine is readily absorbed and reaches peak concentration in the blood 1-hour after taking it and is maintained for 3-4 hours. So, it is the window just before exercise that is best to take and then ‘top-up’ with additional dosing during endurance events of several hours in duration.

So how much caffeine do you need to take? Although early research was conducted using high doses of caffeine (6 mg and above of caffeine per kg body weight), more recent research indicates that lower doses can provide similar performance benefits with less negative side effects. Individual responses to caffeine vary but typically doses in the range 1-3 mg caffeine per kg body weight is sufficient to improve performance i.e. for a 70 kg athlete, that’s a range of 70 to 210mg.

So, what does that sort of dosage of caffeine look like? For context, a typical average espresso may contain around 100 mg of caffeine, so two strong cups of coffee could easily get an athlete at or close to the 3 mg per kilogram of body weight figure. Because the caffeine content of coffee can be quite variable and not all beverages may be suitable, the use of caffeine tablets such as NoDoze are popular which give a defined and known dose of caffeine. Then there are the popular energy drinks, energy shots and gels which can contain caffeine, in which case the caffeine dosage should be given on the label. For example, a Red Bull contains 80 mg of caffeine per can, but there are energy drinks that contain even higher doses. Tea, chocolate and cola can also be sources, but the amount of caffeine in them is much lower.

The research field of caffeine has mostly used it in a pure form, with very little research looking at ‘real world’ use by drinking coffee and for good reason as the caffeine content of coffee can be so variable. But there could be other beneficial chemicals in the coffee bean outside of the caffeine. In fact, one study in eight trained male triathletes found that laboratory cycling time-trial performance was 5 percent better and with greater power output when using either coffee or pure caffeine compared to a non-caffeine placebo drink or decaffeinated coffee. So, coffee and caffeine are both able to improve exercise performance, but in this study, the caffeine content of the coffee was measured so it could be compared against pure caffeine. The one point for budding athletes to be aware of is that the amount of caffeine in coffee can be quite variable, meaning it is hard to know exactly what dose a person is having.

Not everybody responds the same to caffeine and there is some evidence that this could be because of genetics where the presence or absence of a genetics variations in a gene called CYP1A2 - can mean a person is either a rapid or slow metaboliser of caffeine and this could explain some of the variation in responses to caffeine seen in clinical trials.

Side effects

The possible sports benefits of using caffeine must be weighed up against its downsides. And that’s a risk of increased heart rate, anxiety and over-arousal, sleep disturbances and gastrointestinal upsets if you take too much of it or are sensitive to it. Caffeine’s effects on hydration though are likely very much over-stated, especially in habitual consumers (that’s you, coffee addicts) with fluid balance studies showing little impact on hydration at the doses that have been shown to enhance performance. And more so, caffeine is normally consumed with fluid, so this adds to the positive side of the fluid balance equation.

Caffeine is one of the few nutritional supplements for which research has consistently shown a sports performance benefit. The use of all supplements and sports foods by athletes though involves a balance between the potential benefits set against potential risks such as health side-effects, anti-doping rule violations from contamination, and redirection of resources from real performance-enhancing factors. So, take this into account when considering taking any sports supplement. And seek out personalised advice from a sports dietitian. You can connect with an Accredited Sports Dietitian as well as access a great range of resources through the website of Sports Dietitians Australia at www.sportsdietitians.com.au

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.