Drinking coffee first thing in the morning may seem like a great way to wake up, but it can actually trigger digestive issues, raise stress hormones, and cause jitteriness or a racing heartbeat.
Digestive Problems
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Coffee contains several types of acids—such as chlorogenic acid and N-alkyl-5-hydroxytryptamine—that stimulate the production of stomach acid. Stomach acid helps break down food, move it through the intestines, and absorb nutrients. But when you drink coffee on an empty stomach, the extra acid can worsen acid reflux or gastroesophageal reflux disease (GERD).
Coffee’s natural bitterness also encourages more stomach acid production. Without food to buffer it, this acid can irritate the stomach lining, leading to heartburn, nausea, indigestion, or symptoms of irritable bowel syndrome (IBS). If you notice these problems only when drinking coffee without eating first, consider adjusting the timing or amount of coffee you drink.
Elevated Stress Hormones
Cortisol, the body’s main stress hormone produced by the adrenal glands, helps regulate metabolism, blood pressure, and blood sugar. Normally, cortisol peaks naturally when you wake up, then declines through the day and rises again early in your nighttime sleep cycle.
Coffee stimulates additional cortisol production. For some people, drinking coffee while fasting can push cortisol levels even higher. Chronic elevation of cortisol can lead to inflammation, increased risk of type 2 diabetes, Alzheimer’s disease, heart disease, and even uncontrolled weight gain.
Other Potential Side Effects
Coffee on an empty stomach may alter brain chemistry and cause anxiety, restlessness, palpitations, or even panic attacks. Many people also report headaches, migraines, or elevated blood pressure when drinking coffee without eating first.
Expert Recommendations
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Limit total coffee intake to about 400 ml (roughly 2–3 cups) per day.
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Eat a balanced breakfast before drinking coffee to protect your stomach and reduce hormone spikes.
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Good pairings include yogurt, scrambled eggs, breakfast sandwiches, banana bread, or other light baked goods.