How Coffee Affects the GI Tract

Coffee has a whole host of benefits for a person’s health. But coffee drinkers can also be prone to heartburn and other gastrointestinal problems. The fact is that there are quite a few gi effects of drinking coffee, both positive and negative. That being the case, we present a short summary of how coffee affects the GI tract. Our article relies heavily on information from a review of the literature article published in Nutrients in 2022. Our treatment of this issue starts at the top of the gi tract.

Coffee and Salivary Enzyme Production

The first effect of coffee on the digestive system happens in the mouth with increased secretion of an enzyme that helps digest starches (polysaccharides). Studies have shown that drinking coffee can increase secretion of the salivary enzyme alpha-amylase and/or not affect it. Interestingly, the effect is more pronounced with cold as opposed to hot or warm coffee. The level of salivary enzyme increase appears to be unrelated to any gastrointestinal symptoms or complaints.

Coffee and Secretions in the Stomach

When we eat something and it arrives in the stomach, the stomach responds by secreting hydrochloric acid as well as digestive enzymes like lipase, pepsin, and chymosin. When we drink coffee it increases the secretion of hydrochloric acid. Caffeinated coffee does this more robustly than decaffeinated coffee. While coffee increases the amount of acid secreted it does not affect how quickly the stomach empties. Thus, food and excessive acid may remain in the stomach for the normal length of time.

How Coffee Affects the GI Tract

Coffee and Problems of the Esophagus and Stomach

Most folks who are interested in how coffee affects the gi tract also have gi problems after drinking coffee. They get heartburn, upset stomach, gas, nausea, etc. A major issue for gastro-esophageal reflux is incompetence of or relaxation of the lower esophageal sphincter, the band of muscles that normally keeps stomach contents and acid from going back up the esophagus. Coffee appears to decrease the effectiveness of the lower esophageal sphincter with, in turn, can allow stomach acid reflux into the esophagus. This can be a problem because, unlike the stomach which tolerates a high level of acid, the esophagus does not. The acid causes irritation, inflammation, ulceration, scaring, and even Barrett’s esophagus, which can lead to esophageal cancer.

It should be noted that many other dietary factors as well as obesity typically contribute to gastro-esophageal reflux.

Coffee and the Gallbladder and Pancreas

When partially digested food passes out of the stomach it goes to the duodenum where gallbladder and pancreatic enzymes are added. Coffee is known to increase both bile production from the gallbladder and contractility of the gallbladder via the hormone cholecystokinin. This effect happens with both caffeinated and decaffeinated coffee. Cholecystokinin also stimulates the pancreas to secrete other enzymes that help digest starches, proteins, and fats. Another effect of coffee is that it appears to reduce the incidence of gallstones at the rate of about a 5% decrease per cup of coffee per day.

Coffee and Bacterial Populations in the Intestinal Tract

There is a lot of research showing that coffee consumption can affect the relative levels of three most common types of bacteria in the lower intestinal tract, Bacteroides, Prevotella, and Ruminococcus. There do not appear to be all that many significant effects on health due to how coffee affects these bacterial levels.

Coffee and Cancer of the GI Tract

Numerous studies have shown that drinking coffee slightly reduces the risk of cancers of the mouth, esophagus, stomach, liver, and gallbladder. There does not appear to be an association be risk of cancer of the large intestine and coffee consumption.

Common Sense and Coffee Consumption

All of the research into coffee and gi tract issues involves large groups of people and statistical significance. For the individual it is a different issue. If you find that drinking too much coffee regularly results in heartburn, cut back on you consumption. If you can drink coffee without problems by drinking only with a meal, do that. If you blood pressure is high and reliably goes up with three or four cups of coffee a day, cut back on your consumption. In the end, common sense will be your best guide if you think coffee is causing problems in your gastrointestinal tract.

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