Coffee drinkers already intuitively know that their favorite beverage has a stimulating effect on the gut. For many, this happens first thing in the morning, and is usually seen as a positive boost to get the day started. This blog post sets to outline some of the common effects that coffee may have on the human gut and digestion.
For more context, a 2020 survey conducted by the National Coffee Data Trends (NCDT) reports that 7 in 10 Americans drink coffee every week, and 62% drink coffee every day [1]. The same survey found that the average American coffee drinker consumes about 3 cups per day. That’s a lot of coffee, so it’s important to understand any impacts on the digestive system.
Coffee Relaxes the Intestines
Coffee stimulates the release of gastric juices in the stomach and provokes “peristalsis” of the intestines [2]. This is due to the caffeine, polyphenols, and acidic compounds in coffee. These properties are why it may feel like your gut literally moves after drinking coffee. This phenomenon is peristalsis: the involuntary constriction and relaxation of smooth muscles, such as the intestines. These contractions move the contents of the gut down the digestive tract. In many people, this leads to a trip to the bathroom. There’s nothing wrong with a little encouragement from coffee!
Since coffee stimulates the release of gastric juices in the stomach, it may aggravate pre-existing “GERD” symptoms (Gastro-esophageal reflux disease; heartburn), but there is no evidence to hint that coffee drinking causes GERD [3]. Coffee, and more notably caffeine, can cause the sphincter between the stomach and esophagus to relax, which can lead to heartburn-like symptoms if stomach acid goes into the esophagus [4]. In some sensitive individuals, this feels like “heartburn.” Thankfully, there are many techniques to deal with coffee acid and its impact on the stomach. For more information on acid in coffee, heartburn, and ways we deal with these considerations, please check out this blog post: https://aeroastery.com/coffee-acid-friend-or-foe/ .
Coffee Improves Gut Microbiome
Moving lower in the digestive system, it is clear that coffee impacts the microbial communities that live inside our intestines. Most of the research on coffee’s effects on the gut microbiome have been conducted on animals in laboratory settings. Those studies can provide great insights into what could happen in a human body. For now, let’s ignore the animal studies and focus on exciting human science.
A team of researchers in 2019 looked at “the association between caffeine consumption and the composition and structure of the colonic-gut microbiota.” [5]. The researchers took small biopsies of mucus from the intestines of 34 healthy participants and sampled the microbial composition. The participants were then asked about their coffee consumption, which correlated with caffeine intake. The results from this study show that higher caffeine consumption from coffee was associated with increased “richness and evenness of the mucosa-associated gut microbiota.” The concepts of “richness” and “evenness” in the gut microbiome are up for debate, but the researchers also found a higher relative abundance of anti-inflammatory bacteria, such as Faecalibacterium and Roseburia and lower levels of potentially harmful Erysipelatoclostridium.
The study is unique and important for microbiome research and the science behind coffee. Past studies have focused on the microbial composition of stool samples, while this current study focused on mucus biopsies from the intestines. Direct biopsies of the gut may more-accurately reflect the composition of the microbial communities that line the human digestive tract. These communities create the “human microbiome,” which has health ramifications related to mental health, liver health, and metabolic status like obesity and cholesterol levels [6]. Much more research is needed on the effects that coffee has on the microbiome.
Positive Gut Health from Drinking Coffee
In short, coffee stimulates movement in the gut, which can often result in a trip to the bathroom. Millions of Americans start their day with the reality that coffee has powerful effects on the gut. For most people, this stimulation is a beneficial boost in their morning. Other people may want to try decaf or low-acid coffees, which may slow down the stimulatory effect that coffee has on the gut, or ease any heartburn-like feelings. Coffee can be quite acidic and may affect people with a predisposition for heartburn and GERD, but it does not seem to cause this condition. Amazingly, ongoing research is showing that coffee may create more-favorable conditions in the intestines for beneficial microbial communities to flourish. These communities of gut microbes are associated with positive health outcomes, so, you can enjoy some daily coffee with the knowledge that you might be helping out some bacteria that help you in return. Credible evidence of humans drinking coffee goes back to at least the 15th century [7], so it is not very surprising, but still exciting, to see positive gut-health effects from drinking our favorite beverage.
References:
1] https://www.ncausa.org/Newsroom/NCA-releases-Atlas-of-American-Coffee
2] https://www.britannica.com/video/186989/effects-coffee
3] https://www.jstage.jst.go.jp/article/fstr/19/1/19_1/_pdf/-char/en
5] https://journals.lww.com/ajg/Abstract/2019/10001/196_Caffeine_Consumption_and_the_Colonic.196.aspx
6] https://www.frontiersin.org/articles/10.3389/fmicb.2021.761836/full