Recent news raised questions – again – about the health risks of coffee. How seriously should you take the warnings, and what about the athletic up-side of a little caffeine?

Coffee drinkers in California – and around the world when the news broke – could have been forgiven for spluttering over their morning cup. A court had 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.

While acrylamide is a possible carcinogen, health experts say it’s far from clear whether or not consuming it in food 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.

First, the good.

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.

Most of the studies done on acrylamide so far have not found an increased risk of cancer in humans.

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.

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.

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.

So what about coffee’s downside?

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.

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.

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.