The athletic upside of caffeine

Can we all calm down about coffee? It’s one of the most commonly consumed drinks in the world, yet it’s often perceived as a potentially dangerous habit that needs to be kicked. But why? Research shows caffeine can serve up plenty of perks – particularly when it comes to athletic performance.

Coffee drinkers in California – and around the world – could be forgiven for spluttering over their morning cup. A Californian court recently ruled that coffee sellers must now display signs warning customers their drink of choice contains acrylamide, a potentially dangerous chemical created when coffee beans are roasted. But, while acrylamide is a possible carcinogen, health experts say it’s far from clear whether it increases cancer risks in humans. The American Cancer Society says we should be cautious, but notes “most of the studies done [on acrylamide] so far have not found an increased risk of cancer in humans”. More research is needed, they say

Coffee is never far from a headline. It’s the fuel that runs many of us. It’s something we enjoy. It’s part of many cultures. But we’re never sure whether it’s good or bad for us. Maybe because coffee and caffeine have been so widely studied, the question of whether they are good or bad seems to be, well, both.


Caffeine has been shown to reduce sleepiness and increase alertness, as anyone who’s ever used an espresso to power up after a sleepless night knows. Caffeine from coffee can also, it seems, improve athletic performance and endurance. In a review published in 2015 researchers found that between 3 and 7 milligrams of caffeine per kilo of body weight increased endurance performance by around 24 per cent – not insignificant. It’s thought that because caffeine stimulates and boosts alertness, it allows athletes to train harder, for longer.

Caffeine has been on the list of banned substances for athletes in the past, although not currently, despite being an acknowledged performance enhancer. It’s being “monitored” by the World Anti-Doping Agency (WADA) but as yet hasn’t been re-listed.

So for non-athletes, can coffee enhance a workout? It’s possible, based on the current research, that we may experience the same endurance-enhancing effects as athletes do. Caffeine’s benefits peak about an hour after ingestion, so having a coffee an hour or so before a workout would be the best way to see if it works for you. Going easy on the milk and sugar means you won’t cancel out your workout’s benefits with extra calories.

It is possible caffeine helps muscles burn more fat, but the evidence is conflicting so far.

There’s much hype online about the potential of caffeine as a “fat burner”, and it’s included in supplements to supply this reputed benefit. It is possible caffeine helps muscles burn more fat, but the evidence is conflicting so far. There is some research associating caffeine with weight loss. But it’s not a magic solution.


A 2020 study has shown that compounds in coffee may have anti-obesity properties, and women who drink two to three cups of coffee a day are likely to have lower total body fat than those who don't. In men, the relationship was also apparent, but much less significant. Interestingly, the anti-obesity properties can’t be pinned on caffeine – the findings were consistent whether it was caffeinated or decaffeinated coffee that was consumed!

Coffee may also have some other benefits in disease prevention: it’s linked with reduced risk for type 2 diabetes, Alzheimer’s, Parkinson’s disease and liver cancer. Coffee, like tea, also contains antioxidants which are beneficial to health.


The main thing to note is that caffeine has a long half-life: about six hours, depending on the individual. That means that six hours after your espresso drink, half of its caffeine is still in your system, and could stay there for even longer. Not a problem at 2pm; potentially an issue at 10pm, because caffeine interferes with the duration and quality of your sleep. You might fall asleep, but have less of the deep, restorative sleep you need to wake up feeling rested.

If you’re worried … lay off the coffee in the late afternoon and evening, and if you’re finding sleep a problem, try cutting back.

Too much caffeine – which is classed by the FDA as both a drug and a food additive – can also have other side-effects, including nervousness, heartburn, constipation and diarrhoea. Longer-term effects include impaired judgement, emotional fatigue, mood swings, depression and anxiety.

If you’re worried you might be overdoing it, lay off the coffee in the late afternoon and evening, and if you’re finding sleep a problem, try cutting back.

There are few official guidelines on how much coffee is okay. It’s partly because we all tend to process caffeine at different rates; one person’s mellow buzz turns another into a jittery wreck. I’m a two-coffee-a-week person; I know someone who happily drinks five or six coffees a day. Pregnant women are advised to limit coffee to about one a day.

What’s more, the caffeine in a cup of coffee can vary widely – from 80mg to 150mg, depending on the variety and how it’s roasted and brewed. Espresso has more caffeine than instant coffee, and cold-brew coffee can pack an even heftier punch. Large coffee drinks, of course, have more caffeine. It can be tricky to know how much you’re getting in a specific cup.

So where does that leave us with our morning double-shot? As with everything, moderation is a good idea. And as always, it pays to look at the big picture. In a plant-based diet full of colorful, whole foods, a little coffee can be enjoyed without worry.


Relying on a morning coffee to kickstart your day is not the only option. Recent research shows that a short cardio session can stimulate the same effect as caffeine – plus you get the added bonus of all the other health benefits exercise serves up. The scientists also found that coffee withdrawal in the morning doesn't actually affect working memory – and a brisk 20-minute walk was able to reduce other caffeine withdrawal symptoms, particularly fatigue and a depressed mood.


Coffee and its impact on human health have been the subject of hundreds of studies as well as meta-analyses – that is, studies of other people’s studies. Mostly, at least in the last couple of decades, those studies have failed to show any evidence that coffee does harm and, in fact, some evidence that it could offer some health benefits.

It could, for instance, protect against heart disease. A large study of 25,000 adults from South Korea published in 2015 found that people who drink between three and five cups of coffee per day were less likely to have calcium deposits in their coronary arteries, which is an early indicator of cardiovascular disease.

A paper published the year before, in which researchers combined the results of 36 studies involving more than 1,270,000 people, showed that moderate coffee consumption was inversely associated with cardiovascular risk1; those who drank about three to five cups a day were at the lowest risk for coronary problems, and those who consumed five or more cups a day had no higher risk than those who didn’t drink it at all.

The news gets even better. A meta-analysis published in 2011, which included 59 studies suggests that coffee is associated with a reduced risk of pancreatic, liver, breast and prostate cancer. Another published in 2015, which looked at three big groups of health professionals, showed that drinking five cups a day was associated with a reduced chance of death of all causes, compared to people who didn't drink coffee at all.

Anyway, in 2015, the U.S.D.A. dietary guidelines (which for the first time assessed the impact of coffee on human health) concluded that three to five cups of coffee wouldn’t be bad for us, that there’s good evidence that coffee-drinking was associated with reduced risk of type 2 diabetes and cardiovascular disease, and moderate evidence of a protective association between coffee and Parkinson’s disease.

And this year the World Health Organization (WHO), which had classified coffee as “possibly carcinogenic to humans” in 1991, reviewed 500 relevant and more recent epidemiological studies, and cleared it of that classification.

A cautionary note; WHO still says there seems to be an association between drinking coffee that is too hot (more than 65C or 149F) and cancer of the oesophagus. (This is based largely on evidence of a link between cancer and maté drinking in South America, as well as animal studies.)

Of course, an “association” does not establish cause and effect, and many of the studies have limitations. There are over 1000 chemicals in coffee, some of which have credible health benefits, including substances that have been shown to reduce resistance to insulin and calm inflammation. But what compounds could be involved and how they might work has yet to be understood.

Niki Bezzant is a New Zealand-based food writer, editor and commentator. She is the founding editor (now editor-at-large) of Healthy Food Guide magazine, and is currently president of Food Writers New Zealand and a proud ambassador for the Garden to Table program which helps children learn how to grow, cook and share food. She is a member of the Council of Directors for the True Health Initiative, a global coalition of health professionals dedicated to sharing a science-based message of what we know for sure about lifestyle and health.