Caffeine appears in all manner of places, from your morning cup (or three) of coffee, to the pills you pop when you’ve got the flu, or the bar of chocolate you chomp down on of an afternoon. In fact, caffeine is the most widely used psychoactive substance in the world.

It’s also no stranger to being in the news for its possible impacts on health – recent weeks have seen its advocates promoting its apparent benefits, whilst others slam it for its alleged risks. But who’s right? Both and neither, it turns out.

Heart health

Some research suggests caffeine might actually be beneficial for our hearts. In an analysis of three large heart disease studies, researchers found that higher coffee intake was associated with a lower risk of heart failure. Sipping on decaf didn’t have the same effect, indicating that the effect could be down to caffeine, though further research is required to fully validate this theory.

That being said, researchers have identified some short-term cardiovascular impacts when it comes to the consumption of highly caffeinated drinks. High levels of consumption – considered to be about one liter (34 ounces) of fluid containing 320 milligrams of caffeine, which is the same as four 250-milliliter (8.5-ounce) cans of Red Bull – has been found to cause temporary incidences of increased blood pressure and heart palpitations.

It's an effect seen particularly keenly when energy drinks are combined with alcohol – so maybe go easy on the Jägerbombs.

Metabolic health

A study published last year found that people with higher blood caffeine levels might have a lower risk of obesity and type 2 diabetes. These individuals had variants in two genes associated with caffeine metabolism, meaning their bodies were slower to break the molecule down and thus it remained at a high level in their blood. 

However, this research does have limitations: half of caffeine’s effect was thought to have been mediated through weight loss, for example. Another important factor to note is that the study primarily included people of European ancestry, meaning the findings might not apply to everybody. Further research would need to be done to determine whether upping caffeine intake might play a role in reducing the risk of these two conditions.

Mental health

Caffeine is a stimulant – a lot of people have a coffee or an energy drink for an early morning or mid-afternoon boost, not just to our energy levels, but our moods. How does it do this? As part of the American Medical Association’s What Doctors Wish Patients Knew™ series, neurologist Dr Nicole Clark explained that caffeine “stimulates dopamine, which is a chemical in your brain that plays a role in pleasure motivation and learning.”

On the flip side, if you already have experiences with conditions like panic disorder and anxiety, recent research suggests caffeine might make things worse for your mood. A 2022 meta-analysis found that consuming roughly five cups of coffee worth of caffeine induced anxiety in both people with panic disorder (PD) and in healthy individuals, but those with PD were at higher risk of having a panic attack.

Fetal health

Caffeine is capable of crossing the placenta, meaning it can end up in a growing fetus’s bloodstream. Research in this area has indicated that daily consumption of more than 300 milligrams can be associated with an increased risk of low birth weight, whilst more than 350 milligrams can be linked to pregnancy loss. 

As such, whilst many healthcare organization guidelines state that pregnant people can still have some caffeine if they want to, they advise no more than 200 milligrams a day. However, a 2020 study concluded that a growing body of research suggests there is no safe level of caffeine consumption during pregnancy.  

Sports performance

Caffeine supplementation is a well-established trend in fitness and sports performance, with the substance often added to pre-workout powders in varying amounts. Research has generally suggested that it can improve athletic performance; although much of that work is based on data from male athletes, sports nutrition bodies have applied it in their guidelines generally.

In a meta-analysis of studies in female team sports athletes, researchers found that caffeine supplementation was indeed effective at increasing some aspects of performance, like handgrip strength and countermovement jump, but not in others (agility, squat jumps, repeated sprint ability). It concluded that more research was needed before current ideas about caffeine could be applied to all. 

There’s also been some suggestion that coffee in particular can improve performance across a range of different activities, but how much, if any, of that effect is down to the specific action of caffeine is unclear.

The overall picture

All this being said, what makes caffeine “good” or “bad” likely depends on the person: how well your body metabolizes it, medications you might be taking that could interact with it, or how much you consume. 

However, it’s worth remembering that caffeine is a drug and caffeine toxicity or overdose is very much a thing – a rare thing, but it can be fatal. Best to be cautious with it then, particularly when it comes to caffeine supplements.

The Food and Drug Administration (FDA) has advice on what to look out for when figuring out how much caffeine is too much for you. Symptoms might include:

• Insomnia
• Nausea/upset stomach
• Headache
• Jitters and/or anxiousness
• Feeling unhappy

If you are looking to cut back on caffeine, it’s generally recommended to do so gradually. Though going cold turkey might not be dangerous like it is with other drugs, it can still have some fairly unpleasant side effects, like headache and fatigue, so it’s best not to immediately throw all your coffee beans in the bin.

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.