Coffee lovers, gym-goers, and productivity hackers, this one's for you.

Caffeine is the most widely consumed psychoactive substance in the world, yet myths and misunderstandings still swirl around our favourite stimulant. Does it dehydrate you? Make you lose fat? Give you heart problems? Help with exercise? Or all of the above?

To answer these questions once and for all, a team of leading researchers recently published an exceptional paper titled:
 
“Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show?”

This review pulled together decades of scientific research, including meta-analyses and clinical trials, to give evidence-based answers to the 15 most common caffeine questions. And the results might surprise you.

Here’s what the science actually says, no hype or guesswork.

1. Does caffeine dehydrate you?

Not unless you're drinking excessive doses.
Habitual coffee drinkers can rest easy. Moderate caffeine intake (think 2 to 4 cups of coffee) doesn’t increase urine output or lead to dehydration, even during exercise.

2. Will it dehydrate you during workouts?

Still no.
Studies show caffeine doesn’t negatively impact hydration status when you’re properly replacing fluids. Just sip water like you normally would.

3. Does it help you lose weight or burn fat?

Kind of, but don’t rely on it.
Caffeine can boost fat oxidation during exercise, especially in untrained individuals. But its effect on long-term weight loss is small and inconsistent.

4. Is caffeine better for upper body or lower body strength?

It helps with both, but not equally for everyone.
Some research suggests it may benefit upper-body exercises like bench press more than squats. But overall, the effects depend more on dose, activity type, and the individual.

5. Does caffeine affect your mood or risk of depression?

It can go both ways.
Moderate caffeine intake may protect against depression, but too much can trigger anxiety, poor sleep, and low mood, especially in sensitive individuals.

6. Can you overdose on caffeine?

Yes, but you’d have to try really hard.
Fatal caffeine overdoses are extremely rare and usually involve pure caffeine powders or supplements. Your morning cup of coffee is safe.

7. Do men and women respond differently to caffeine?

Sometimes.
Women may metabolise caffeine more slowly, especially when using oral contraceptives. But overall, caffeine works as an effective performance aid for both sexes.

8. If I drink coffee every day, will a pre-workout still work?

Yes, but you might need a slightly bigger dose.
Regular caffeine consumers can still benefit from acute supplementation, though 6 to 9 mg per kg of body mass may be more effective.

9. Does caffeine work for everyone?

Almost.
While some people don’t feel much, true non-responders are very rare. Most of us get at least some performance boost, although it can vary day to day.

10. Is it bad for your heart?

Not in moderate amounts.
Caffeine can temporarily raise blood pressure and heart rate, but moderate consumption is not linked to increased cardiovascular risk. In fact, it may be protective in some cases.

11. Can caffeine weaken your bones?

Possibly, if you're drinking 9 or more cups of coffee a day.
Doses above 400 mg per day might impact bone mineral density, particularly in women, but more research is needed. Stick to 4 cups or fewer and you’re likely in the clear.

12. Is caffeine safe during pregnancy?

Lower is better.
Most guidelines recommend keeping intake below 200 mg per day while pregnant, roughly two small cups of coffee. Even small amounts may carry some risk, so caution is wise.

13. Is caffeine addictive?

Not really, but withdrawal is a thing.
Caffeine can cause dependence and withdrawal symptoms like headaches and fatigue, but it doesn’t meet the full criteria for a true addiction.

14. Should you delay caffeine for 90 minutes after waking to avoid a crash?

That trend has no real scientific backing.
There’s no evidence that delaying your morning coffee prevents an energy dip later. If you’re tired in the afternoon, it's probably more about sleep than coffee timing.

15. What’s the bottom line on caffeine?

Caffeine is safe, effective, and wildly popular for a reason.
Used wisely, it can boost performance, enhance mood, and sharpen mental focus. Just don’t go overboard, and remember that individual responses vary.

What you add to your caffeine matters

Caffeine on its own is safe and, for many people, beneficial. But the way it’s delivered can make a big difference. A strong black coffee or plain tea is a world apart from a venti cappuccino loaded with syrup and cream.

Those sweetened drinks might feel like a harmless treat, but over time they can contribute to excess calories, unstable energy levels, and weight gain. The caffeine may sharpen your focus, but the sugar could be quietly undermining your health goals.

If you're drinking caffeine for performance, energy or mental clarity, keep it simple. A splash of milk? Fine. But if your coffee looks and tastes like dessert, it might be time to rethink the habit.

Too much, too late? How caffeine affects your sleep

For all its benefits, caffeine's biggest drawback is its impact on sleep. Even if you fall asleep easily, a late-afternoon coffee can reduce your total sleep time and disrupt the quality of your deep, restorative sleep stages.

Caffeine has a half-life of around 5 hours, but in some people, it can linger in the system for much longer. That means a 3pm pick-me-up could still be affecting your brain at 10pm. Not only does poor sleep make you tired the next day, it increases cravings, disrupts blood sugar, and reduces motivation to exercise.

The fix is simple: know your cut-off time. For most people, keeping caffeine intake to the morning or early afternoon and limiting the total dose to under 400 mg per day (about four cups of coffee) is enough to stay out of sleep trouble. If you’re sensitive, you might need even less.

Final word

This new review cuts through the noise and confirms what many of us suspected: caffeine isn’t the villain it’s often made out to be. Used wisely, it’s a helpful tool for energy, mood and performance.

So enjoy your brew—just be mindful of what comes with it.