According to experts, your gut is adaptive, but there are a few facts to bear in mind.

I’ve heard that consuming coffee on an empty stomach in the morning can cause harm to the stomach lining. Is that correct?

For many individuals, starting the day without a freshly prepared cup of coffee is inconceivable. Some social media users, however, have asserted that drinking a sip without food could be harmful to your gut or lead to other ailments such as bloating, acne, hair loss, anxiety, thyroid problems, or uncomfortable periods.

Kim Barrett, a professor of physiology and membrane biology at the University of California, Davis School of Medicine and a member of the governing board of the American Gastroenterological Association, stated that researchers have been studying the benefits and risks of drinking coffee, particularly as they relate to the gut, since the 1970s. The stomach is resistant to all types of irritants, including coffee.

“The stomach has numerous defence mechanisms,” stated Dr. Barrett. For instance, it secretes a thick layer of mucus that acts as a formidable barrier between the stomach lining and whatever is ingested. She noted that this shield also shields the stomach from its own natural acidic environment, which is required for food digestion.

“For the stomach’s defences to be breached, you’d have to swallow a really abrasive material, as it’s continually exposed to a very harmful environment,” she explained. This is how the stomach does its function.

How does coffee influence the digestive tract?
Alcohol, cigarette smoke, and nonsteroidal anti-inflammatory drugs like ibuprofen (Advil, Motrin) and naproxen (Aleve) are known to alter the stomach’s natural defence mechanisms and damage the lining, according to Dr. Byron Cryer, chief of internal medicine at Baylor University Medical Center in Dallas.

His research laboratory focuses on determining how various drugs and substances can affect the stomach and small intestine. While certain irritants can increase the stomach’s susceptibility to acid and ulcer formation, this is not the case with coffee, according to many large-scale studies. Even among those who drank three or more cups of coffee per day, a 2013 study of almost 8,000 Japanese participants found no significant relationship between coffee consumption and ulcer formation in the stomach or intestine.

Even in its most concentrated form, coffee is unlikely to cause objective damage to the stomach, according to Dr. Cryer. And significantly less at the typical dosages found in common beverages.

Nevertheless, coffee has an effect on the gastrointestinal tract; it can stimulate the colon and cause a bowel movement, and it promotes the formation of stomach acid.

Outside of the gut, the caffeine from coffee is well known to increase heart rate and blood pressure. And if you drink it too close to bedtime, it can disrupt your sleep. But these changes are temporary, Dr. Cryer said.

Will increased stomach acid cause any issues?

Drinking coffee on an empty stomach is unlikely to cause any damage to your stomach, but it could theoretically provoke heartburn, Dr. Barrett said.

We know that coffee sets off stomach acid production, but if you have food in your stomach, or if you drink your coffee with milk or creamer, that will aid in creating a buffer that helps to neutralize that acid. So drinking coffee, especially if it’s black, without a meal can reduce the stomach’s pH more than it would if you drank it with milk or with a meal, Dr. Barrett said.

Although a slightly lower pH is no problem for your stomach lining, it could pose an issue for the lining of your esophagus because it is far more vulnerable to damage from acid. Furthermore, a few studies have shown that coffee can relax and open the sphincter that connects the esophagus to the stomach, which hypothetically could allow acid from the stomach to more easily splash upward into the esophagus and cause unpleasant heartburn symptoms.

But even there, the data is mixed. A 2014 review of 15 studies across Europe, Asia and the United States found no link between coffee consumption and heartburn symptoms, while, in contrast, a 2020 study using data from more than 48,000 female nurses found a higher risk of heartburn symptoms among coffee drinkers.

To understand how coffee might affect the esophagus, scientists also study a condition called Barrett’s esophagus, which occurs when the esophagus is damaged from chronic exposure to stomach acid, such as in people with longstanding acid reflux issues. With this condition, the cells lining the esophagus morph into hardier, stomach-like cells to protect themselves from the acid. These changes can increase the risk of esophageal cancer, especially if you have a family history of the condition or if you smoke. But reassuringly, a 2016 study of veterans in the United States found no similar relationship with coffee consumption. The authors concluded that for Barrett’s esophagus, avoiding coffee would probably not be helpful.

So what should I do?

Practically speaking, as a gastroenterologist, I usually tell my patients to take note of their symptoms. If they consistently notice a burning pain in their chest or a sour taste in their mouth after drinking coffee, they may want to cut down — or consider an antacid. Adding a splash of milk or cream or a small bite of food with your morning cup can also help. But if you aren’t noticing any symptoms, you’re probably someone who doesn’t experience significant reflux after coffee and can keep drinking it in peace.

Dr. Cryer regularly enjoys his coffee as a latte or cappuccino — the steamed milk cuts down the bitterness, he said. And, in general, he added, coffee drinking has many health benefits, including links to longevity, a lower risk of cardiovascular disease and protection against many cancers, including liver, prostate, breast and colorectal cancer.

“There’s far more evidence for coffee’s benefits than harms,” Dr. Cryer said — which is something worth keeping in mind, he added, while you scroll through social media stories that profess the brew’s detriments.