Ask an expert: Is it bad to drink coffee on an empty stomach? (2025)

Coffee is the backbone of many people’s morning routine – the UK drinks an estimated 98 million cups of coffee a day,with 87 per cent of drinkers enjoying their cup in the morning. But rumours swirl around whether this habit – especially when consumed on an empty stomach – can have negative consequences for our health.

To start with the bad news, upper GI surgeon Myutan Kulendran at King Edward VII’s Hospital says that “coffee itself is acidic, and the increase in acid in the stomach can also cause reflux”.

Avoid if you have heartburn or acid reflux

Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London (KCL), elaborates, saying that “coffee, particularly black coffee, is a well-known gastric irritant. It stimulates gastrin secretion which increases acid secretion. People with acid reflux problems are generally advised to avoid drinking it on an empty stomach.”

Some studies have shown that coffee can relax the sphincter connecting the stomach to the oesophagus, meaning stomach acid could be more likely to easily reach the oesophagus and cause heartburn. It’s thought that this is due to the caffeine content or something in the coffee itself, as the same effect has been observed when drinking decaf coffee.

Add milk to ease negative effects

If you are susceptible to heartburn or acid reflux, adding a splash of milk might help – milk proteins are thought to potentially bond to the components within coffee that cause the problems. But for most people, there is good news.

“There really is no evidence that I’m aware of in the literature that says [coffee first thing] is in any way, shape or form, bad for you,” Kim Elaine Barrett, vice dean for research and distinguished professor of physiology and membrane biology at the UC Davis School of Medicine says decisively.

“I think it’s fair to say that if you’re caffeine sensitive, coffee first thing is not a good idea. But millions of people do have a cup of coffee first thing without having eaten anything, and it has no adverse effect on them. The most common thing that people say is that it gives them some heartburn or gastric comfort. But even that is addressable.”

Coffee can induce bowel movements

While the acidity of coffee can be a worry (particularly because of how it seems to increase the stomach’s acidity), fears that coffee can damage the stomach lining or cause major digestive issues, Kim adds, have not been reflected in evidence.

“Any time you put anything in your stomach, it’s going to initiate a reflex to secrete more acid into the stomach. So if you don’t have any other food there to buffer it, you are at risk for heartburn. But it’s not really going to do anything negative to the stomach itself, because the stomach secretes a lot of mucus that’s a protective blanket over the surface of the stomach.” Unlike the oesophagus, the stomach has built in tools to protect itself from acid.

The only impact coffee does seem to have on digestion is that it can speed up the colon, helping to induce bowel movements. However, this is less a result of coffee than it is of timing.

“Putting anything in your stomach can have a laxative effect,” Kim explains. This is because when we rise, we have a reflex that signals our colon to wake up when we change from lying to standing up. There’s also the gastrocolic reflex, which means that if you put something in your stomach, it also sends a signal to the colon to get things moving because other stuff is on its way.

In any case, whether that is a negative or positive is a matter of perspective. “I’ve seen anecdotal evidence in the literature that people say that’s why they have a cup of coffee in the morning, because it helps them go to the bathroom,” Kim adds.

Keep an eye if you are sensitive to caffeine

The other suggested impacts of a coffee first thing are that it can affect your heart and increase your stress levels. But according to Dr Jonathan Behar, consultant cardiologist at King Edward VII’s Hospital, says that he only advises patients to watch their caffeine intake in specific circumstances.

“As a heart rhythm specialist, I see a lot of patients with palpitations and dizziness, things like that. And one of the things that I’ll talk to them about is caffeine and the effect of caffeine on those palpitations. Sometimes reducing caffeine has a positive impact and reduces the incidences. But that’s the only element where we get involved.”

The fact that coffee is a stimulant is also seen as a risk. Our cortisol levels are at their highest when we wake (in order to wake us up and get us going) and drinking coffee also stimulates cortisol production, which is thought to be worrisome.

But studies have found that if you drink coffee regularly, the production of cortisol rises much less than it does in occasional drinkers – and in some cases doesn’t rise at all. Whether you have a full or empty stomach doesn’t appear to change this conclusion. And just as our stomachs are built to handle acid, our bodies are built to handle elevated levels of cortisol over short periods of time, as is the case when caused by caffeine.

Ultimately, the negative impacts of coffee are not shaped by when you drink it necessarily – but simply by the fact of drinking it at all.