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Whether it be enjoyed as a quick energy boost or a comforting warm drink during slow mornings, coffee is a popular beverage choice for most. The effect of caffeine goes beyond its ability to increase energy and alertness – it has also been associated with lowering the risks of cardiovascular diseases, type 2 diabetes, Parkinson’s disease, and newer research even suggests that heavy coffee drinkers may have a healthier gut microbiome than non-coffee drinkers.

Microbial Diversity

Drinking coffee may help increase beneficial microbial species in the gut. In one clinical trial with 34 adults aged 50-75 years, researchers evaluated the effects of caffeine intake on microbial diversity and composition. They discovered that heavy coffee consumption, about 2 cups daily, was associated with a higher diversity of Alistipes and Faecalibacterium counts, and lowered Erysipelatoclostridium counts compared to those who drank less coffee (less than 1 cup daily). These findings are notable because Faecalibacterium is anti-inflammatory, while Erysipelatoclostridium has been shown to be harmful in excessive amounts. Therefore, the composition changes appear to be beneficial. Another finding worth highlighting is that individuals with high caffeine and coffee intake consumed significantly more riboflavin (vitamin B2) than those consuming less caffeine. Riboflavin is an essential vitamin for gut bacteria, as it helps shape the diversity and richness of gut microbiota. Some studies suggest that this B vitamin promotes butyrate production, which helps maintain a healthy gut barrier. Thus, the researchers predict that this prebiotic may partially explain the microbial differences in those consuming more caffeine. Another study reveals that these effects may also be attributed to the polyphenols found in coffee as well.

Polyphenols

Coffee contains several chemical components, including caffeine, polyphenols, polysaccharides, and minerals. A 2020 study reveals that changes in gut microbial composition may in fact be attributed to polyphenol content in coffee, as well as caffeine. In this study, researchers observed an increase of the Bacterioides-Prevotella-Poprhyromonas group among those drinking up to 2 cups of coffee per day. Out of these microbial groups, Bactereroides are the most beneficial, helping with nutrient digestion, vitamin production and immune modulation. Therefore, they play a key role in shaping a healthy gut microbiome. The researchers explain that Bacterioides bacteria can also metabolize polyphenols better than other bacterial groups. Like riboflavin, polyphenols act as prebiotics, feeding good bacteria and limiting the growth of harmful bacteria. They differ from riboflavin in the sense that polyphenols are not created in the gut, rather they are only present in the gut upon intake. This is worth noting because 20% of the polyphenols that the participants consumed came from coffee. Thus, the team predicts that polyphenols from coffee were able to interact with intestinal bacteria in two ways: 1) by modifying the gut environment, or 2) by being metabolized by intestinal bacteria and being converted into compounds with antioxidant activity.

Energy Drinks and Tea

While these studies suggest that caffeine consumption may have positive effects on the gut microbiome, it is important to note that not all caffeine sources will behave the same way. For example, energy drinks, often having more caffeine than coffee, have been shown to reduce bacterial diversity in the gut. These effects may be attributed to the sugar content rather than the caffeine content in energy drinks. High doses of sugar from energy drinks may create unfavorable shifts in microbial diversity and contribute to poorer metabolic health. Other than energy drinks, tea is another popular source of caffeine that has been found to affect the gut microbiome in several ways. Many studies reveal that drinking green tea can increase Bifidobacteria species, although the effects are mainly related to the polyphenol content found in teas, rather than the caffeine. Therefore, polyphenols from coffee and tea can act as a prebiotic, which can help increase beneficial bacteria and create a healthier gut microbial composition.

Overall, quality human research on this topic is limited. While some studies reveal that people who drink more coffee have higher microbial diversity, higher anti-inflammatory (like Faecalibacterium) and beneficial bacteria, further research is warranted to better understand how many cups of coffee can elicit these beneficial outcomes without it affecting other factors such as sleep and anxiety.