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Energy

Is caffeine bad for you?

16/05/20243 min read

Written byLaura Harcourt

Reviewed byEmma Kinrade

glass mug of milky coffee, with ground coffee, sugar and butter in pots, with a metal coffee pot

Whatever form it comes in, caffeine is a go-to for many of us seeking an energy boost. Find out how caffeine works and whether or not it’s good for you.

Summary

1The effects of caffeine

Research shows that the levels of adenosine – the hormone that controls feelings of tiredness – can build up in your central nervous system...

Jump to details below

2The possible benefits of caffeine

We know, so far, that caffeine can give your energy levels a much-needed boost, but what else can it do for you? Some of the possible benefits...

Jump to details below

3The potential side effects of caffeine

Dependency - Caffeine is a drug, so you can become dependent on it. If you don’t give in to your body's caffeine cravings, research highlights...

Jump to details below

Jump to section

What is caffeine?
The effects of caffeine
The possible benefits of caffeine
The potential side effects of caffeine
What’s the acceptable daily limit of caffeine?
Who should avoid caffeine?
The final say
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Explore related topics

Energy

A morning cup of Joe, an afternoon cuppa, a night shift energy drink… all these things have one thing in common – caffeine!

Caffeine features pretty heavily in most of our everyday lives, but how much do you know about what it is, how it affects you and how much is safe to have?

We’re taking a deep dive into the world of caffeine to look at whether it’s good for you, bad for you or a little bit of both.

Sideways young woman of African American ethnicity wear t-shirt drink coffee read book close eyes sits in armchair stay at home flat rest relax spend free spare time in living room indoor grey wall

What is caffeine?

Caffeine is the world’s most popular drug. Yep, you read that right.¹

It’s a naturally occurring chemical compound found in the fruit, leaves and beans of coffee, cacao and guarana plants. When extracted in its pure form, it’s a white, bitter-tasting powder.¹

In our day-to-day lives, it can be found in all sorts of drinks and food items, including coffee, tea, fizzy drinks, energy drinks and chocolate. It can also be found in energy supplements and some medications, such as cold and flu remedies.¹

The effects of caffeine

Research shows that the levels of adenosine – the hormone that controls feelings of tiredness – can build up in your central nervous system throughout the day, helping you to fall into a deep sleep at night.²

When you consume something that has caffeine in it, your liver breaks it down to release stimulating chemicals which are quickly absorbed into your bloodstream.^2,3

It’s thought that caffeine blocks the effects of adenosine by binding to adenosine receptors in the brain. According to some studies, this not only lowers adenosine levels but it can also affect the levels of other important hormones that help control sleep. In addition to this, caffeine may also increase the activity of your central nervous system and stimulate your brain, thus increasing your energy levels and alertness.^2,3

These stimulatory effects may begin 15 to 30 minutes after consuming caffeine, and can last several hours.³

How long it takes for a caffeine buzz to wear off may depend on a few factors such as your age, body weight and if you smoke cigarettes. Generally, it takes around four hours for just half of a dose of caffeine to be metabolised (processed) by the body.³

The possible benefits of caffeine

We know, so far, that caffeine can give your energy levels a much-needed boost, but what else can it do for you? Here are some of the possible benefits caffeine may have.

These benefits aren’t yet backed by robust scientific evidence as research into all these potential effects is in its infancy. Much more carefully designed studies with larger human clinical trials are needed to conclude these findings.

1. May improve athletic performance

A research review has shown that caffeine can have a positive effect on physical performance in both regular people and professional athletes.⁴ So, a hit of caffeine before a workout might just help you reach your personal best in the gym or on the tarmac.

There’s also evidence showing that caffeine can have a pain-blocking effect, which may aid recovery from delayed-onset muscle soreness (DOMS).^5,6

2. May support your mental function

According to a meta-analysis of the effects of coffee on depression and depressive symptoms, those who consumed higher levels of caffeine were at a lower risk of depression than people who consumed less or no caffeine.⁷

More research is needed, but a recent study also suggests that caffeine may have a significant positive effect on short- and long-term memory, and may help with learning too.⁸

3. May protect against disease

Some studies in rats and humans found that ingesting coffee every day may be linked to a slower decline in cognitive function and attention, and could also lower your chance of developing Alzheimer’s disease.⁹

More studies are needed to know for sure, but another study showed that caffeine could slightly reduce the risk of developing dementia too, but in women only. However, results are mixed at the moment and further high-quality research is required.¹⁰

4. May support liver health

Emerging research has found that coffee may reduce your risk of liver damage, including scarring and cirrhosis, and may also lower your chance of developing a type of liver cancer called hepatocellular carcinoma.^11,12,13

There’s also some evidence that suggests that coffee can also slow the progression of liver disease and even reduce the chance of premature death.¹¹

5. May lower your risk of gout

One recent UK-based study found that drinking six cups of tea or three cups of coffee a day could reduce your risk of developing gout by as much as 23% and 40%, respectively.¹⁴ However, more research is needed to confirm this.

Find out more about foods that are linked to gout and living with gout.

6. May support gut health

Research has found that coffee can positively impact your gut microbiome due to its prebiotic properties, fostering the growth and activity of good gut bacteria. Drinking coffee regularly may also lower harmful species of microbes in the gut.^14,15

Home Espresso Machine Pouring Fresh Coffee Dual espresso shot being poured into clear mugs on a modern home espresso machine, with scattered coffee beans and houseplants in the background

The potential side effects of caffeine

Despite the many benefits of caffeine, it can have some downsides.

1. More anxiety

A meta-analysis from this year revealed levels of cortisol, commonly known as the stress hormone, may be significantly increased by caffeine, especially if the dosage is greater than 400mg. So, while caffeine can boost energy levels, it may also make you feel jittery and elevate feelings of anxiety.¹⁶

Consuming too much caffeine can also disrupt your sleep and speed up your heartbeat, which can make you feel more anxious.¹⁷

Want to learn more? Visit our article, ‘Does caffeine cause anxiety?’.

2. Dependency

When all is said and done, caffeine is a drug, so you can become dependent on it.

If you don’t give in to your body's caffeine cravings, recent research highlights that it can potentially cause withdrawal symptoms, such as fatigue, low mood, headaches, brain fog, irritability and difficulty concentrating.¹⁸

3. Digestive issues

Due to its laxative effect, many people rely on their morning coffee to keep things regular.

But you need to be careful not to drink too much, as some research reveals that coffee can increase your risk of digestive issues, including poor digestion, nausea, heartburn, burping and wind.¹⁹

4. Increased blood pressure

Drinking more than four cups of coffee a day might increase your blood pressure.

If you’re worried, cutting down or choosing decaf alternatives can keep your blood pressure in check.^20,21

What’s the acceptable daily limit of caffeine?

Healthy adults should limit their caffeine intake to 400mg per day. It’s important to know that some people are more sensitive to the effects of caffeine than others, so you may need to limit your intake to less than this.²²

Keep in mind that although ‘decaffeinated’ versions of most drinks are available, most still contain small amounts of caffeine.²²

Use this guide to help you keep track of your caffeine intake:²³

mug of instant coffee – 100mg
mug of filter coffee – 140mg
mug of tea – 75mg
can of cola – 40mg
250mL can of energy drink – 80mg
50g of plain dark chocolate – less than 25mg
50g of plain milk chocolate – less than 10mg

worker holding coffee beans in his hands checks the quality of coffee after it has been roasted in coffee machine

Who should avoid caffeine?

Caffeine is safe for most adults to have in moderation.

If you’re pregnant or breastfeeding, it’s advised by the NHS that you limit your caffeine intake to no more than 200mg a day maximum, as regularly drinking more than this may increase your risk of pregnancy complications. However, it’s still generally advised to avoid caffeine completely during pregnancy.^24,25

If you’re worried about how caffeine may interact with any medications or affect a medical condition, we recommend speaking to your GP for personalised advice.

The final say

Whether you’re just getting into having a coffee in the morning before work or relying on energy drinks to get you through a night shift, remember that moderation is key.

Aim to have no more than 400mg a day and we’re sure you’ll be able to keep your caffeine habit a healthy one.²⁶

Disclaimer

The advice in this article is for information only and shouldn’t replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

Sources

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Muljadi JA, et al. Effect of caffeine on delayed-onset muscle soreness: A meta-analysis of RCT. Bull Natl Res Cent. 2021;45(1):197. DOI: https://doi.org/10.1186/s42269-021- 00660-5
Hurley CF, et al. The effect of caffeine ingestion on delayed onset muscle soreness. The J Strength Cond Res. 2021;27(11):3101–09. DOI: https://doi.org/10.1519/JSC.0b013e3182a99477.
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Huangda Guo, et al. Dose–response relationships of tea and coffee consumption with gout: a prospective cohort study in the UK Biobank. Rheumatology. 2023;62(9):3043–3050. DOI: https://doi.org/10.1093/rheumatology/kead019.
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