For most people, drinking a cup of coffee on an empty stomach is unlikely to cause problems, but one cup of coffee can worsen symptoms for people with sensitive stomachs, those predisposed to certain gastrointestinal problems, such as gastroesophageal reflux, or those who have already damaged the stomach lining, such as those with ulcers.
Kim Barrett, professor of physiology and biology, says that cortisol, the stress hormone, is usually higher in the morning and, for some people, a dose of caffeine can increase the effect.
Cortisol can also raise blood sugar levels, and those with diabetes who drink coffee on an empty stomach may have problems with blood sugar levels.
Studies show that coffee can be acidic and stimulate the production of stomach acid, but this is not likely to be a problem for most people. A study of 8,000 healthy individuals found no significant association between coffee consumption and four major upper gastrointestinal disorders, including ulcers and reflux problems.
"As for the stomach, it's extremely well equipped to protect itself," Barrett said, adding that coffee "isn't likely to damage the lining of the stomach unless there's some underlying disease.
Depending on how the coffee is brewed and served, you may be able to partially bypass the acidity issue.
Experts suggest that you try black coffee as it tends to stimulate less acid secretion in the stomach.
Drinking iced coffee. The cold drink was found to have lower concentrations of acidic compounds than the hot drink.
Add milk or cream to your coffee. Milk can help soften stomach acid.
In the end, experts agree that for most people, drinking a cup of coffee on an empty stomach won't cause any harm. Even those with sensitive stomachs may be able to reduce the risk of an upset stomach by preparing their coffee with milk.