For millions of people around the globe, the day doesn’t truly begin until that first cup of coffee — often consumed within minutes of waking and frequently on an empty stomach.
But what actually happens inside the body when coffee is the very first thing one takes in, before food, water, or any other nourishment?
Dr. Shannon Lavery, a dietitian and health coach with close to 20 years of experience, has broken down the science behind this morning habit, examining its effects on gut health, cortisol response, and overall metabolic function.
While social media warnings often paint a dramatic picture, the reality is more nuanced and grounded in physiology rather than fear-based claims.
A closer look at the effects of drinking coffee first thing in the morning
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Claims that drinking coffee on an empty stomach causes adrenal fatigue — characterized by reliance on caffeine to function, poor stress tolerance, and sleep issues — are among the most widely discussed concerns online.
Other frequently circulated claims suggest that drinking coffee without eating can “burn a hole in the stomach lining” or cause “stomach ulcers.”
Dr. Shannon Lavery wrote in a June 7 article for taste.com.au that these claims are highly exaggerated.
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She noted that all that drinking coffee on an empty stomach does is trigger the release of stomach acid, with the amount varying depending on whether the coffee is caffeinated or decaffeinated.
At most, it relaxes the valve between the esophagus and stomach, which can allow acid to move upwards and potentially trigger reflux symptoms.
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Speaking about stomach ulcers specifically, Dr. Lavery said they are more commonly linked to H. pylori bacterial infections or the overuse of anti-inflammatory pain-relief medications.
Though coffee does not cause stomach ulcers on its own, she said it can exacerbate existing ulcers by stimulating acid production, so those suffering from the condition should avoid it.
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Coffee is also not very good for people with anxiety, as it blocks adenosine, a neurotransmitter that promotes relaxation.
Dr. Lavery also challenged the notion that coffee is responsible for morning alertness, pointing instead to a hormone that plays a much larger role
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If delaying the morning coffee worries one, they should rest assured, as cortisol is already taking care of waking the body.
The hormone has a bad reputation because it is linked to stress, weight gain, and other health issues when levels are chronically elevated, but the hormone is not that bad at all.
It plays an important role in regulating the body’s circadian rhythm (biological functions in response to the day-night cycle), helping one feel energized in the morning, per Dr. Lavery.
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Cortisol levels naturally rise shortly after waking up and peak within the first 30 to 45 minutes of being awake.
They then gradually decline throughout the day, reaching their lowest point at night.
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Drinking coffee immediately upon waking, therefore, may not provide a noticeable energy boost because the body is already naturally alert due to cortisol.
Coffee lovers are recommended to wait at least an hour or two before having their first cup.
The question of when to consume your last cup of coffee was previously addressed by another doctor
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Coffee should have a cut-off time of 2 pm — one hour before the dreaded 3 pm slump — according to Dr. Nighat Arif, a resident doctor for BBC Breakfast and ITV’s This Morning.
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During a February 2026 appearance on the latter show, Dr. Arif said the cutoff time was reached after a study of 2,000 participants who reported sleeping better on days when they did not consume caffeine in the late afternoon.
She explained that the effect is directly linked to coffee interfering with the production of adenosine, which, with its relaxation-promoting effects, helps facilitate sleep.
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She added that the cut-off time does not apply to those whose work schedules fall outside the traditional nine-to-five, as they may need coffee to keep them awake late at night.
“I will drink coffee as soon as my one eye is open,” a netizen said
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