How much caffeine is really in your drink? The best and worst options

Many of us don’t even realise how much we rely on caffeine until we try to cut down. Photo / 123rf

Filter coffee, black tea, Diet Coke – some drinks contain a lot more than you think. Here’s how to drink it safely.

Many of us can’t get through the day without our favourite pick-me-up, whether it’s a frothy coffee, a cup of builders' or ice-cold Diet Coke, but often we have no idea of the amount of caffeine in any of the drinks we’re consuming – and the effect on our bodies.

According to Nichola Ludlam-Raine, a dietitian and the author of are, for most healthy adults, consuming up to 400mg of caffeine a day is considered safe.

“Roughly, that’s equivalent to four cups of brewed coffee, eight cups of tea or five cans of energy drink, though amounts vary widely between different drinks,” she warns.

But with the highs come the lows, as many of us don’t even realise how much we rely on caffeine until we try to cut down.

“Caffeine is an addictive psychostimulant,” warns Professor Tim Spector, the co-founder of nutrition company Zoe, “and anyone who has tried to give it up will be familiar with the effects of withdrawal, including tiredness, headaches and bad mood.

Caffeine is an addictive psychostimulant. Photo / 123rf

“Importantly, we all respond to caffeine differently; some people can have a weak coffee and feel highly anxious for the next eight hours. For these people, it’s best to avoid caffeine as the health benefits won’t outweigh the negatives.”

If you want to make sure you’re drinking caffeine safely, here’s how much there is in a variety of the most popular brews from coffee to fizzy drinks (and some surprising foods that can also give you a caffeine kick).

Double espresso

The good news, says Ludlam-Raine, is that a couple of shots of the hard stuff (usually the highest in caffeine of most drinks at 1.3mg per 100ml) is rich in polyphenols, a group of compounds found in plants that have anti-inflammatory and antioxidant properties. It can also enhance cognitive function and increase alertness, and may reduce the risk of neurodegenerative diseases and Type 2 diabetes.

But, she warns, such a highly concentrated caffeine intake “can lead to jitteriness, anxiety, digestive discomfort and poor sleep”. Also, black coffee is acidic and may irritate sensitive stomachs.

Filter coffee

In terms of pros and cons, the health benefits of filter coffee are on a par with espresso, but the slightly lower caffeine concentration per serving means it’s less intense. Like espresso, it contains antioxidants such as chlorogenic acids, which have anti-inflammatory properties and studies show it may help regulate blood sugar. Because you’re more likely to pour a bigger mug than you would drink espresso in, “it can be dehydrating in excess, may raise blood pressure temporarily and could impact sleep quality if consumed too late in the day”, warns Ludlam-Raine.

If you enjoy the taste, but are keen to cut down, try lower caffeinated coffee, suggests Lucy Kerrison, a consultant gastrointestinal dietitian. “Some varieties are naturally lower in caffeine; for example, some arabica beans are only 40-60% of the strength of most traditional coffee beans,” she says.

“These options are naturally lower in caffeine (compared to many decaf or ‘half-caff’ varieties, where there are additional processes and chemicals used to remove or reduce the caffeine content.” Robusta beans (also known as canephora) pack the biggest caffeine punch, so avoid those if you’re trying to limit your intake.

Kerrison says lower-caff coffee is worth switching to for “those who want the benefits of coffee without too many jitters, those who are looking to slowly reduce their caffeine intake, or those who experience gastrointestinal upset with coffee but do not want to go cold turkey”.

A cup of decaf coffee might still give those sensitive to caffeine a psychological boost. Photo / 123rf

Decaffeinated coffee

Even coffee billed as decaf does contain trace amounts of caffeine, says Spector, “but not enough to produce an energy boost”.

For those who don’t tolerate caffeine well, or have been advised to cut down for health reasons, making (and smelling) a cup of decaf coffee might still give you a psychological boost if it’s part of your morning routine.

And Spector is a fan. “Decaf coffee still contains all the health-promoting polyphenols of caffeinated coffee, making it a great option for anyone who likes the taste of coffee but doesn’t like the buzz.” Surprisingly perhaps, Spector also adds that coffee also contains fibre, “a nutrient that the majority of us don’t get enough of”.

“Fibre helps protect against heart disease, metabolic conditions and cancer. So, whether caffeinated or not, coffee can help move you towards your recommended daily amount. And [a] recently published study found that drinking coffee (caffeinated or decaffeinated) was linked to specific, positive changes in the gut microbiome.”

Energy drinks

Huel powder was first introduced in 2017, then the ready-to-drink bottles became popular with medics who were too busy to eat meals during the pandemic. Those 500ml bottles had flavours, including iced coffee caramel, which contained around 65mg of caffeine, but the purpose was more as a meal replacement to fill you up.

In 2023, the British company launched a new, lighter variation in the form of an energy-boosting fizzy drink. Each tin boasts the same amount of caffeine as coffee which it says is “naturally sourced from coffee beans”.

In Ludlam-Raine’s opinion, these are “a healthier type of energy drink”. She says that each can provides 26 vitamins and minerals as well as the 100mg caffeine. “So it’s a good, fruit-based option for those who want a natural caffeine boost but dislike the taste of coffee,” she says. “It’s less ultra-processed than other energy drinks and although it contains one sweetener, sucralose, but that’s just one, so there are fewer additives overall.”

Black tea

A cup of regular black tea with milk contains around 47mg of caffeine [0.24mg of caffeine per ml].

“Black tea tends to have less caffeine per cup than coffee, but it can vary wildly depending on how long you steep the bag,” explains Spector.

Other factors to take into account are that loose tea has a higher concentration of caffeine than what you’d find in a bag, and the water temperature also makes a difference (the hotter it is, the more caffeine is released).

“Drinking black tea may protect against heart disease and stroke,” says Spector. “The health benefits from tea are likely a result of plant chemicals called polyphenols in the tea leaves.”

“The healthiest way to enjoy black tea is without sugar and milk,” adds Spector. “Added sugars are always best avoided where possible, and milk reduces the amount of polyphenols your body absorbs.”

The caffeine level remains mostly unchanged regardless of adding milk. However, the milk proteins may potentially slow down the absorption of caffeine, making the “hit” feel less intense.

Research shows drinking green tea regularly may be associated with lower heart disease and mortality risk. Photo / 123rf

Green tea

A cup of green tea typically contains 30-50 mg of caffeine [0.2mg of caffeine per ml].

“Compared with coffee and black tea, green tea has less caffeine,” says Spector. But it’s worth swapping out the odd cup of regular tea or coffee for green tea because of the other health benefits it brings."

Research suggests drinking it regularly may be associated with lower heart disease and mortality risk, but Spector believes this is probably because of the plant compounds in tea, rather than the caffeine. “For instance, early evidence suggests that green tea’s catechins [a substance found in tea that helps protect cells from damage caused by free radicals] may support healthy weight loss and protect brain health.”

If you want more “boost” than green tea, matcha is a powder made from the leaves of green tea, suggests Kerrison. “It comes with a higher caffeine concentration [around 40-170mg per cup], as well as a high concentration of phytochemicals [natural plant chemicals].”

Fizzy drinks

A can (330ml) of regular Coca‑Cola and Coke Zero both have 34mg of caffeine [0.1mg of caffeine per ml], while Diet Coke has 46mg [0.13mg of caffeine per ml].

According to Kerrison, the general rule of thumb when it comes to cans of pop and caffeine, is that “the darker coloured fizzy drinks, such as Coke, Pepsi and Dr Pepper, are the ones that contain caffeine, or have caffeine added to them, whilst the lighter fizzy drinks usually don’t”.

Caffeine-free options are available and these are slightly preferred by Ludlam-Raine as “they won’t affect sleep or cause caffeine-related side-effects”. But she wouldn’t recommend we frequently drink them, either. “They still contain sugar or artificial sweeteners, which can negatively impact metabolic health if consumed in excess, at the expense of a healthy whole food diet. Acidity may contribute to dental erosion too, and no one wants rotting teeth!”

Spector says any fizzy drink is best enjoyed just once in a while because they tend to be packed with artificial additives and sugar.

“Of all the ultra-processed foods that scientists have studied, fizzy drinks have one of the strongest links to poor health outcomes, including Type 2 diabetes and obesity.”

Hot chocolate

A Grande cup (480ml) of Starbucks hot chocolate contains 25mg of caffeine, though some sachets you’d make with water at home contain around 5mg per mug.

Most of us think of hot chocolate, generally made with milk, as a soothing night-time drink. But like anything containing chocolate, it contains some caffeine. How much really depends on the different brands, how it’s made, how strong you like it and your preferred mug size.

It might be just enough to lift your mid-afternoon slump, without affecting your sleep in the way coffee drunk later on can affect you, suggests Ludlam-Raine. “The cocoa in hot chocolate provides flavonoids that may support heart and brain health,” she says.

But it’s not all good news. “The drink is often high in sugar, which may contribute to weight gain and blood sugar spikes, plus some brands contain added emulsifiers and thickeners, meaning they are technically classed as ultra-processed.”

Ovaltine, she suggests, might be a better bedtime option for children who like a milky drink. The malt-based drink is caffeine-free and contains added vitamins and minerals, such as iron and B vitamins, which may be beneficial, particularly for children. If mixed with milk instead of water, you will be getting more calcium too.

Yerba maté is a herbal product with a strong flavour somewhere between traditional tea and coffee. Photo / 123rf

Yerba maté

Derived from the Ilex paraguariensis tree, which is native to South America, this is a herbal product with a strong flavour somewhere between traditional tea and coffee. “It’s generally consumed as a tea and is rich in the same polyphenol chlorogenic acid that coffee is, as well as various flavonoids, vitamin C and contains some B vitamins, for energy,” says Kerrison.

The reason caffeine is found in plants is thanks to its ability to act as a natural pesticide, protecting them from insects that attempt to eat their leaves.

Yerba maté is sold online, in health stores and larger supermarkets either in powder form, loose tea, or teabags.

“The caffeine content can vary widely depending on the types of leaves used and how the tea is prepared,” she adds. “There are some preliminary trials to show yerba mate may reduce LDL (bad cholesterol), although larger trials are required.”

Energy drinks

Red Bull was the best-selling energy drink in the UK last year, generating around £410 million ($926.5m) in sales, yet, as widely reported, “energy drinks are bad news”, says Spector. “Aside from the caffeine content, which can be very high, they often include high levels of added sugars and a raft of additives, which coffee doesn’t.”

The second-biggest-selling energy drink in the UK was Monster (£357m in sales), which has the same amount of caffeine and also contains additives such as guarana, taurine and L-carnitine.

While British-created Lucozade has been around since the 1920s and was seen as a beverage to give more “pep” to the unwell, it has seemingly been rebranded as an energy drink and has various flavours. It contains 60mg of caffeine per 500ml.

“Research shows that regularly consuming these drinks is linked to many side effects, including insomnia, depressive symptoms and gastrointestinal upset,” warns Spector. “If anyone needs a caffeine boost, they should opt for something else.”

Foods that contain caffeine

Caffeine isn’t just in drinks, Ludlam-Raine reminds us.

“It’s found in chocolate and some medications, including pain relief tablets. So being mindful of your total intake from all sources is important, particularly for those sensitive to caffeine,” she says.

Dark chocolate (containing at least 50% cocoa) has around 12mg per 1oz chunk: “The flavonoids support heart and brain health, but some varieties are high in sugar,” says Ludlam-Raine.

Milk chocolate has around 6mg per 1oz chunk: “It’s lower in caffeine but often high in sugar and fat, making it more of an occasional treat,” she says. White chocolate contains no caffeine.

Some chewing gums have added caffeine marketed to give you a “boost”, says Kerrison. These are best avoided as the release of caffeine is rapid and they also include artificial sweeteners (not good for a sensitive gut and some sweeteners can negatively impact the microbiome).

For caffeine-sensitive individuals, Kerrison often recommends pairing their caffeinated drink with food to slow the absorption of caffeine, reducing its irritating effect on the gut, or sipping slowly.