Hey,

It's time for another instalment of the Vitamin––the weekly fitness newsletter that helps you be healthier, stronger, and leaner while navigating fitness bullshit.

Do you really need to delay your morning coffee?

(and other caffeine myths)

I'm sitting here at 3 am writing this newsletter because my daughter decided that, instead of sleeping, she would much rather wake up at this ungodly hour and sing "head, shoulders, knees, and toes." So after 15 mins of touching my head, shoulders, knees, and yep, you guessed it, my fucking toes, my pint-sized overlord finally decided that was enough and went back to sleep.

The only reason I can function is thanks to the cup of coffee I'm sipping on while writing this.

But, according to some people on the internet, consuming caffeine within an hour or two of waking up will cause me to crash by the afternoon.

Is this true, though?

A group of sports nutrition experts came together, like the science Avengers, to address 14 common questions and misconceptions about caffeine. [1]

I'm way too sleep-deprived to go through every single one, so we'll only focus on three in today's Vitamin. The paper is open-access if you want to read the full text.

1-Do you need to wait an hour or two after waking before consuming caffeine to avoid the afternoon 'crash'?

Short answer: No.

Long answer–

This is a myth put forward by a popular 'science' YouTuber. It goes something like this–

Adenosine builds when we're awake and reduces when we sleep. Cortisol – generally known as the stress hormone – also increases in the hours after waking and clears residual adenosine from your system, lowering adenosine further in the hours after waking.

If you consume caffeine immediately after waking, you block the binding of adenosine to its receptor. As adenosine continues to build, your energy levels nose-dive off a cliff by the afternoon, and you 'crash'.

However, if you delay caffeine by a few hours, you give adenosine a chance to bind to its receptor and be cleared, helping you avoid the afternoon crash.

But here's the thing: Adenosine actually increases rapidly after waking (a matter of minutes) and stabilises while you're awake. In the hours before sleep, the opposite happens––there's a rapid decline of adenosine, which then plateaus while you're asleep.

To quote the researchers:

To avoid feeling sluggish in the afternoon, you could simply have caffeine at lunch or early in the afternoon. This seems reasonable, except with some caveats.

Sleep is important for health and recovery, and caffeine intake can reduce how long it takes for you to fall asleep and how long you sleep. Therefore, it's probably a good idea to limit caffeine intake in the later afternoon.

To minimise the effect of caffeine on sleep, it's recommended that coffee (~100mg caffeine) be limited to 8 hours before sleep and pre-workouts (220mg caffeine) be limited to 13 hours before sleep.

2-Does caffeine dehydrate you?

Short answer: Maybe. But not by a meaningful amount.

Long answer–

A 2015 meta-analysis [2]––i.e. a statistical study of studies––found caffeine had a significant effect on diuresis when the average intake was 300mg/day (approximately 2-3 coffees per day).

However, significant doesn't always mean practically relevant, and the difference amounted to ~100ml per day, which the researchers concluded was insufficient to meaningfully influence daily hydration. Additionally, this small effect on diuresis wasn't evident when exercise was added to the mix.

In summary, the authors of the present study conclude that sweat rate, hydration strategy, and genetics influence hydration much more than caffeine intake.

3-Do you need to 'cycle off' caffeine to retain its benefits?

The best evidence for this claim comes from a recent meta-analysis [3] that assessed whether habitual caffeine consumption affected the benefits of caffeine on exercise performance. It concluded that habitual caffeine intake didn't affect the benefits of caffeine on exercise performance.

Overall, the current evidence suggests that we can have our coffee and drink it too (to improve exercise performance).

Here's the TL;DR version of a few other questions the researchers looked at–

• Does caffeine increase fat loss? Recent research doesn't support the use of caffeine as a fat loss aid.
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• Does caffeine affect upper vs lower body strength differently? No, caffeine intake can increase both upper and lower body strength similarly.
  ​
• Can too much caffeine kill you? Yes, but it's extremely rare. For healthy individuals consuming caffeine via tea or coffee, no.
  ​
• Do men and women respond differently to caffeine's effects? While some studies have reported greater performance increases in men, caffeine's ergogenic effects work the same for both men and women.
  ​
• Does caffeine work for everyone? There can be some non-responders to caffeine. But overall, caffeine seems to work for most people.
  ​

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–Aa

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