Coffee on an empty stomach: is it bad for you? What the research says

For many people, coffee on an empty stomach is the first ritual of the day: you get up, switch on the machine and only think about breakfast after the first cup. Online you will easily find warnings that coffee before food ruins your stomach, upsets your hormones and spikes your blood sugar. We checked what the research actually supports, who should be careful and how to drink your morning coffee without irritating your stomach.

Is coffee on an empty stomach bad for you?

The short answer: for most healthy adults, no. There is no convincing evidence that coffee before food damages a healthy stomach or causes peptic ulcers on its own. The main causes of ulcers are Helicobacter pylori infection and non-steroidal anti-inflammatory drugs. Coffee can, however, make heartburn and reflux worse in people who are prone to them. So what matters most is not when you drink coffee, but how your stomach reacts to it.

What happens in your stomach after coffee on an empty stomach?

Coffee stimulates the secretion of stomach acid. Interestingly, decaf does this too, so it is not only caffeine but also other compounds in the brew. In a classic study by Cohen and Booth, published in the New England Journal of Medicine in 1975, both regular and decaffeinated coffee stimulated acid secretion in healthy volunteers, while caffeine alone had only a small effect. The study was small, with 8 people, but it is still widely quoted.

A healthy stomach usually copes with this without trouble. With reflux, peptic ulcers or gastritis, however, coffee may make symptoms worse. If you notice such a link, cut down and talk to your doctor. If you have a sensitive stomach, you will find more practical tips in our guide to coffee and a sensitive stomach.

Coffee on an empty stomach and blood sugar

The study quoted most often comes from the University of Bath and was published in 2020 in the British Journal of Nutrition. It involved 29 healthy adults. After a night in which they were woken every hour, they drank strong black coffee with about 300 mg of caffeine and, 30 minutes later, a sugary drink. Their total blood glucose response was about 50 percent larger than without coffee. That does not mean blood sugar rose by half: peak glucose was only a few percent higher.

It is an interesting signal, but with limits. The study was small and measured a single response to a large dose of caffeine, not long-term effects. It suggests that strong coffee before the first meal may temporarily impair glucose tolerance. It does not prove that moving coffee after breakfast improves blood sugar control in the long run. Still, the researchers suggested eating breakfast first after a bad night and having coffee afterwards, a sensible precaution for people who watch their blood sugar.

Coffee on an empty stomach and cortisol

A popular tip says: don’t drink coffee right after waking up, because cortisol is at its highest then, wait 90 minutes. Caffeine can temporarily raise cortisol, but in regular coffee drinkers the response weakens. In a 2005 study by Lovallo, after a few days of daily intake the morning dose of caffeine no longer raised cortisol, although some people still responded to later doses in the day. There is no convincing evidence that a healthy person needs to wait 90 minutes after waking before having coffee. If you like coffee straight after getting up and feel fine, there is no need to change the habit.

Coffee on an empty stomach, medicines and supplements

This gets less attention but really matters. Coffee can reduce the absorption of some medicines. The best-known example is levothyroxine tablets, the thyroid medicine taken in the morning on an empty stomach. It is taken with water, and the usual advice is to wait at least 60 minutes before coffee. Don’t wash medicines down with coffee. Compounds in coffee can also reduce the absorption of non-haem iron, the kind found in plant foods and some supplements. If you take medicines or iron in the morning, check the leaflet or ask your doctor or pharmacist how long to wait.

Who should be careful with coffee on an empty stomach?

• People with reflux and heartburn: coffee before food may make symptoms worse.
• People with peptic ulcers or gastritis: it is best to discuss coffee with your doctor.
• People with irritable bowel syndrome: coffee stimulates the large bowel, which makes symptoms worse in some people.
• People taking medicines in the morning, especially levothyroxine tablets: keep the recommended gap between the medicine and coffee.
• Pregnant women: according to the European Food Safety Authority (EFSA), up to 200 mg of caffeine a day from all sources raises no safety concerns for the baby.

For healthy adults, except pregnant women, EFSA considers up to 400 mg of caffeine a day from all sources safe, and single doses of up to 200 mg. Not everyone tolerates these amounts well, though. How many cups that is depends on the brewing method. We explain it in how much coffee per day is safe, and you can read more about caffeine itself in caffeine in coffee: facts and myths.

How to drink coffee in the morning without irritating your stomach

1. Eat something small before or with your coffee: a sandwich, yoghurt or porridge. For some people this helps limit discomfort.
2. Choose a coffee that tastes gentle: low in acidity, usually medium or darker roasted. A gentle taste does not guarantee fewer symptoms, though.
3. Try coffee with milk if black espresso before food doesn’t agree with you. Some people prefer it, but reactions differ.
4. Make it smaller: if strong coffee before food doesn’t agree with you, try a smaller cup or a brew with less caffeine.
5. Brew it well: under-extracted coffee can taste overly sour, while a well-brewed cup is more balanced. That is about taste, not about protecting your stomach.
6. Listen to your body: if coffee before food gives you heartburn, move it after breakfast. If not, there is no need to change anything.

Coffee before or after breakfast? A comparison

Which coffee for an empty stomach?

If you prefer a gentle-tasting coffee in the morning, look for low-acid beans, usually medium or darker roasted, with chocolate and nut notes. For the morning we recommend Peru Chanchamayo with notes of sweet chocolate and almonds, Mexico El Jaguar and Brazil Santos Guaxupe. For a bean-to-cup machine, Captain’s Blend works well. All our low-acid coffees are collected in the low-acidity coffee category, and our picks are described in the ranking of the best low-acid coffee beans.

These are suggestions for people who like a chocolatey, nutty profile, not a guarantee of better tolerance. Acidity you taste in coffee is not the same as acid in your stomach. A fruity, light-roasted coffee does not necessarily cause more symptoms than a darker one. If you notice that a particular coffee triggers symptoms, choose the one you tolerate better. We cover this in our article on acidity in coffee.

If caffeine doesn’t agree with you, reach for decaf in the morning: Colombia Excelso Decaf Swiss Water or Mexico El Tucan Decaf. Just remember that decaf also stimulates stomach acid, so it won’t always solve reflux.