gum, gel, or coffee: which caffeine source actually works for performance

quick recap if you missed part 1: caffeine blocks the fatigue signal in your brain, it's proven to improve endurance, strength, and power across basically every metric, and your espresso is wildly inconsistent (anywhere from 25mg to 214mg per cup 🤯). gum absorbs fastest, gels are best for race day, and nasal sprays are a waste of money. [read part 1 here]

the golden rule: more caffeine ≠ more performance. It just means more side effects. The sweet spot is 3–6 mg per kilogram of body weight, and starting at the low end is a sure way to train smart.

here's what 3 mg/kg actually looks like in real life:

If you weigh 55kg / 121lb, your starting dose is about 165mg, that's roughly a strong double espresso, or one and a half caffeinated gum pieces.

If you weigh 65kg / 143lb, you're looking at about 195mg, roughly two caffeinated gum pieces, or two standard cups of coffee (though after reading the barista section, you know that's a gamble).

If you weigh 75kg / 165lb, your starting dose is about 225mg, that's roughly two and a bit gum pieces, or two coffees.

If you weigh 85kg / 187lb, your starting dose is about 255mg, that's two and a half gum pieces, or roughly two and a half cups of coffee.

To put it in everyday terms: 165–255mg is roughly equivalent to one to two large flat whites on a good day. But as we covered in part 1, coffee is the least reliable way to hit a specific number, so if precision matters, gum or gels are the safer bet.

the dose stays the same, but the timing changes.

For shorter runs (under an hour), taking your caffeine 30-60 minutes before you start is enough, because it peaks in your bloodstream around the 60 minute mark and stays active for about five hours.

For longer efforts like a half marathon, some athletes find it helps to split the dose, taking some before and topping up with a caffeinated gel halfway through when fatigue starts to kick in.

For really long events (3+ hours), you can spread smaller doses across the whole effort rather than loading it all up front. Research also shows caffeine hits harder when you're already tired, which is why that late-race gel feels like it brings you back to life.

And if you're just starting out, caffeine can still help, but the performance gains tend to be more noticeable once you've built a fitness base, so don't stress if you're not feeling a huge difference in your first few weeks of running.

fyi, the limit does indeed exist

More than 6 mg/kg doesn't unlock some secret gear. It just makes you jittery, nauseous, and turns your run into a frantic porta-potty search. If you've pooped yourself mid long-run, you'll know to never make that mistake again.

the hidden caffeine trap: caffeine isn't just in your coffee and your pre-workout. It's in chocolate, certain medications, soft drinks, energy bars, even some ice creams. If you're doing the mg/kg calculation (which you should be), you need to account for everything you're consuming throughout the day and not just the intentional stuff before a run.

the pre-workout red flag: a lot of pre-workout supplements hide their caffeine content behind "proprietary blends", which is a fancy way of saying the label says "energy matrix" but won't tell you whether that's 50mg or 300mg. If you're stacking a pre-workout + a coffee + a gel, you could be way over your target without realising it. If the label won't give you the exact number, that's a red flag.

Ever wondered why your friend can sleep fine after a 6pm espresso and you're lying there at midnight like 👁️👁️? It's actually genetics, not tolerance.

There's an enzyme in your liver called CYP1A2 (don't worry about the name, just know it exists) and it decides how fast you process caffeine.

fast metabolisers (AA genotype): you clear it quickly, get the buzz, smash the workout, flush it out, and sleep fine. Honestly? Lucky.

slow metabolisers (AC or CC genotype): caffeine lingers in your system, and a morning cup could still be blocking adenosine at bedtime, quietly destroying your deep sleep and recovery without you even connecting the dots.

the real talk: if coffee makes you feel heavy and panicky instead of fast and light, that's not a mindset issue, it's probably your genotype telling you something. Stick to the lower end of the dose or consider skipping it entirely.

Genetic testing for CYP1A2 is becoming way more accessible now, you can get it through most at-home DNA kits, and it honestly might be one of the most useful things you find out about yourself this year.

Caffeine is one of the only supplements that's actually legit. Safe, effective, and finally being proven to work for female physiology specifically, not just assumed to because it worked on men.

your protocol:

now go caffeine-math yourself into a new PR 💅

— xx, athlete girl

the research behind this article:

Guest N. S. et al. (2021). Journal of the International Society of Sports Nutrition. · Nieto-Acevedo, R. et al. (2025). Nutrients. · Crozier T. W. M. et al. (2012). Food & Function. · Desbrow B. et al. (2007). Food and Chemical Toxicology. · Al-Shaar L. et al. (2017). Front Public Health. · WHO sugar consumption recommendation. · De Pauw K. et al. (2017). International Journal of Sports Physiology and Performance. · Morris C. et al. (2019). Food & Function. · Sadek P. et al. (2017). J Caffeine Research. · Wickham K. A., Spriet L. L. (2018). Sports Medicine.