Episode 262 – 7 Things Worth Knowing About Caffeine

7 Things Worth Knowing About Caffeine

Caffeine is one of the most common performance and energy aids. However, the amount people consume can add up quickly, especially when it comes from multiple sources across the day. This episode covers seven key things worth knowing about caffeine, including common caffeine sources, how long it stays in your system, why people respond differently, and how it can affect training, sleep and anxiety.

Common Sources of Caffeine

Coffee is often the first thing people think of when it comes to caffeine. A standard shot of coffee contains around 80 mg of caffeine, although this can vary a lot.

Energy drinks can also contribute a large amount. In Australia, a typical 500 mL energy drink contains around 160 mg of caffeine. A 250 mL energy drink usually contains around 80 mg.

Pre-workout often ranges from 240 to 300 mg of caffeine, although some products contain more or less than this. NoDoz tablets or capsules contain 100 mg of caffeine.

Other sources include soft drinks, tea, dark chocolate and sports supplements. A standard can of Coke contains about 34 mg of caffeine. Black tea contains around 40 to 50 mg per cup, while green tea contains about 20 mg per cup. Dark chocolate also contains caffeine, with around 20 to 60 mg per 100 g. Some energy gels contain around 100 mg, although others are much lower.

Caffeine Half-life

The half-life of caffeine is typically around three to five hours. However, this can vary a lot between people due to genetics and other factors. For example, if you drink a 200 mg coffee at around 2 pm, you may still have around 100 mg of caffeine in your system three to five hours later. Because of this, caffeine can still affect you even when the obvious effects seem to have worn off.

Why Caffeine Affects People Differently

Some people can have caffeine after dinner and still sleep fine. Others feel wired after having caffeine in the afternoon. This largely comes down to genetics.

The main enzyme involved in caffeine metabolism is CYP1A2, which is found in the liver. Genetic differences in this enzyme can affect how quickly someone clears caffeine. Fast metabolisers clear caffeine more quickly, while slow metabolisers keep caffeine in their system for longer.

Another gene, ADORA2A, influences how sensitive adenosine receptors are to caffeine. This can affect how strongly someone feels caffeine’s effects. For some people, caffeine feels subtle. For others, it can contribute to anxiety symptoms.

Genetic testing is available in Australia and may cost around $100 through direct-to-consumer testing. However, it is also possible to use your own judgement based on how caffeine affects you.

How Caffeine Works

Caffeine does not directly give you energy. Instead, it blocks adenosine receptors in the brain. Adenosine builds up while you are awake. It binds to receptors in the brain and gradually signals fatigue. The longer you stay awake, the more adenosine builds up, and the sleepier you feel. Caffeine blocks this fatigue signal. As a result, it can increase alertness, reduce perceived effort, reduce fatigue and improve focus.

Caffeine and Training Performance

Caffeine can support training performance, but the dose matters.

A dose of 1 to 3 mg per kilogram of body weight can increase alertness and make exercise feel easier. This can indirectly improve performance by reducing rate of perceived effort.

Higher doses, such as 3 to 6 mg per kilogram, can have more direct performance benefits. The top end of this range, around 5 to 6 mg per kilogram, is where stronger performance effects may occur.

The exact mechanisms are complex and still debated. However, possible explanations include changes in the central nervous system, greater motor unit recruitment, stronger muscle contractions and potential changes in fat versus carbohydrate utilisation.

Timing also matters. Caffeine levels in the blood usually peak around 30 to 60 minutes after ingestion. Therefore, taking caffeine at the right time before training makes sense, especially at higher doses.

Lower doses during longer endurance sessions may also help. For example, some lower-caffeine gels may act as a useful top-up during extended exercise.

Caffeine and Sleep

Most people know that caffeine right before bed is not ideal. However, caffeine can affect sleep more than many people realise. A 2023 meta-analysis by Gardiner et al. found that caffeine reduced total sleep time and sleep efficiency. It also increased the time it took to fall asleep. These effects were stronger when caffeine was consumed closer to bedtime. Overall, caffeine reduced total sleep time by about 45 minutes and sleep efficiency by around 7%. That is a meaningful difference, especially for people who care about recovery, training and daily energy.

Caffeine and Anxiety

Caffeine can worsen anxiety symptoms when anxiety is already present. It can also contribute to jitteriness, an elevated heart rate and feeling more on edge.

L-theanine may offset some of the upregulation that can come from caffeine. It does not blunt all of caffeine’s effects, but it may reduce jitteriness, help with focus and lower an elevated heart rate.

Because responses vary between people, it is worth paying attention to your own tolerance. If caffeine makes you feel anxious, jittery or like your heart is racing, your total intake may be too high.

Reducing caffeine can be useful, but going from a high intake to zero can feel rough. Some people prefer to cut down slowly, while others prefer to stop all at once. Either way, testing your own response can help you find the dose that works best for you.

Final Thoughts

Caffeine can be useful for alertness, focus and training performance. However, it can also affect sleep and anxiety, especially in people who are more sensitive or consume it later in the day. The best approach depends on the individual. Consider your total caffeine intake, the timing of your caffeine, and how it affects your sleep, mood, training and anxiety levels.