Caffeine: Facts vs Fiction for Australian Coffee Drinkers

Caffeine is one of the most researched and most misunderstood compounds in the human diet. Australians consume it in enormous quantities — mostly through coffee — yet most of what circulates as "common knowledge" about caffeine is either oversimplified, out of date, or flat-out wrong.

At Jaques Coffee, we grow 100% Arabica in Mareeba, Far North Queensland. Arabica naturally contains less caffeine than Robusta — one of the reasons it tends to produce a cleaner, less harsh cup. Here's a grounded look at caffeine: what it actually does, and what the evidence says about some of the claims you've probably heard.

What Caffeine Actually Does

Caffeine is a naturally occurring alkaloid produced by coffee plants (and tea, cacao, guarana, and others) as a defence mechanism against insects. In humans, it works primarily by blocking adenosine receptors in the brain.

Adenosine is a neurotransmitter that builds up throughout the day and, when it binds to its receptors, makes you feel sleepy and reduces neural activity. Caffeine is structurally similar enough to adenosine that it binds to the same receptors without activating them — effectively blocking the sleepiness signal. With adenosine blocked, dopamine and norepinephrine become more active, which is why caffeine produces alertness, improved mood, and enhanced concentration.

It doesn't create energy — it temporarily masks fatigue. When the caffeine clears your system, adenosine (which has continued accumulating) floods back to its receptors, often producing the familiar post-caffeine tiredness dip.

Fiction: Dark Roast Has More Caffeine

Fact: Light roast typically has marginally more caffeine than dark roast.

This is one of the most persistent myths in coffee. The logic seems intuitive — dark roast tastes stronger, so it must have more caffeine. But caffeine is actually degraded by heat over time. The longer and hotter the roast, the more caffeine is lost. The difference is small (usually less than 10%), and it's largely swamped by other variables like dose and extraction — but the direction of the effect is the opposite of what most people assume.

Fiction: Espresso Has More Caffeine Than Filter Coffee

Fact: A standard cup of filter coffee typically contains more caffeine than a single espresso shot.

A single espresso shot (30ml) contains roughly 60–80mg of caffeine. A standard 250ml cup of filter or plunger coffee typically contains 100–150mg. Espresso is more concentrated — more caffeine per ml — but there's simply less liquid in a single shot than in a full cup of filter coffee.

The caveat: a double espresso or a large milk-based drink built on a double shot (which is standard in most Australian cafés) gets closer to or above a cup of filter coffee in total caffeine content.

Fiction: Caffeine Is Dehydrating

Fact: At moderate doses, caffeine has a negligible effect on hydration.

The idea that coffee dehydrates you is based on the fact that caffeine has a mild diuretic effect — it slightly increases urine production. But studies consistently show that the fluid you consume in coffee more than compensates for the mild diuretic effect, particularly at the doses most people consume (1–3 cups per day).

A 2014 study in PLOS ONE found that moderate coffee consumption produced the same hydration outcomes as equivalent amounts of water in regular coffee drinkers. So while very high caffeine doses can affect fluid balance, your morning flat white is not making you dehydrated.

Fiction: You Should Avoid Coffee After Midday

Fact: The right cutoff depends on your individual caffeine metabolism, which varies significantly between people.

Caffeine has a half-life of roughly 5–6 hours in most people — meaning half the caffeine from a 3pm coffee is still in your system at 9pm. For most people, this is enough to affect sleep quality, which is why an early afternoon cutoff is sensible. But caffeine metabolism varies considerably based on genetics (specifically variants in the CYP1A2 enzyme), other medications, and individual tolerance.

Some people metabolise caffeine quickly and can drink coffee in the evening with no sleep impact. Others are slow metabolisers who feel the effects from a mid-morning cup at midnight. If you're sensitive to caffeine and sleep disruption, an earlier cutoff (noon to 2pm) is prudent. If you're not, you have more flexibility.

Fiction: Caffeine Tolerance Means It Stops Working

Fact: Tolerance affects the stimulant effect more than the cognitive benefits.

Regular coffee drinkers develop tolerance to some of caffeine's effects over time — particularly the cardiovascular effects (elevated heart rate, blood pressure spike) and the jittery, anxious feeling that sensitive people experience with high doses. The adenosine-blocking mechanism that drives alertness and concentration is somewhat more resistant to tolerance development.

What regular coffee drinkers often experience is that caffeine brings them back to their baseline level of alertness more than producing the pronounced lift that occasional users feel. This is partly why habitual coffee drinkers often say they need coffee just to "feel normal" in the morning — the adenosine rebound from the previous day's caffeine is part of what they're clearing.

How Much Is Too Much?

Food Standards Australia New Zealand (FSANZ) considers up to 400mg of caffeine per day safe for healthy adults — roughly equivalent to 4–5 standard espresso-based drinks or 3–4 cups of plunger coffee. Pregnant women are advised to limit intake to 200mg per day.

Individual sensitivity varies widely. If caffeine causes anxiety, heart palpitations, or significant sleep disruption at normal doses, it's worth reducing intake — regardless of what the general guidelines say.

Arabica vs Robusta: The Caffeine Difference

As a grower of 100% Arabica, this is worth noting: Arabica contains roughly half the caffeine of Robusta — 1.2–1.5% compared to 2.2–2.7% by dry weight. This is one reason Arabica tends to taste less harsh and bitter than Robusta (caffeine is itself a bitter compound), and why people who find high-caffeine commercial coffee too jittery or harsh often do better with quality Arabica.

Our Jaques Medium Roast and Espresso Roast are both 100% Queensland-grown Arabica — naturally lower in caffeine, naturally higher in flavour complexity. Grown in Mareeba. Roasted on-site. Sent directly to your door.

Explore our full range at jaquescoffee.com.au.