In a recent study published in the Nutrients journal, researchers in the United States investigated the association between caffeine, coffee consumption, and the colonic microbiome.
Study: The Association between Caffeine Intake and the Colonic Mucosa-Associated Gut Microbiota in Humans—A Preliminary Investigation. Image Credit:Rawpixel.com/Shutterstock.com
Background
Caffeine has been extensively consumed in drinks and food items for decades, increasing alertness and energy. Caffeine has often been associated with lowering the risks of cardiovascular diseases, type 2 diabetes, and Parkinson's disease.
Caffeine consumption has also been associated with lowering the probability of acute and ulcerative colitis, reduced fibrosis among mild-advanced liver fibrosis patients, and lowered the risk of colorectal cancer development.
Coffee reportedly alters intestinal microbiome composition, especially Prevotella abundance. Elevated counts of an anti-inflammatory microbe, Bifidobacterium, have been observed in the feces of individuals with high daily coffee intake. However, data on the relationship between caffeine intake and the colonic microbiome are limited.
About the study
In the present study, researchers assessed caffeine- and coffee-induced alterations in community structure and composition of the human colonic mucosal microbiome, using 16S ribosomal ribonucleic acid (rRNA) sequencing of individuals with healthy colonic tissues, as determined endoscopically.
Individuals residing in Texas, aged 50 to 75 years, were recruited from July 2013 to April 2017 and underwent endoscopy at the Michael E. DeBakey VA medical center (MEDVAMC), to provide polyp-free colonic mucosal biopsy specimens.
The team sequenced microbial deoxyribonucleic acid (DNA) for the polymerase chain reaction (PCR)-amplified 16S ribosomal RNA gene hypervariable region 4.
Coffee (and caffeine) consumption in the previous year was evaluated using food frequency questionnaires (FFQ), and diet quality was assessed using the 2015 healthy eating index (HEI).
The abundance of microbes was compared by low versus high (<83 versus ≥83 mg) intake of caffeine and by none or less than two coffee cups versus two cup intake versus ≥3.0 coffee cups intake.
Multivariate negative binomial-type regression modeling was performed, and the incidence rate ratios (IRRs) were calculated, adjusting for age, ethnicity, body mass index, smoking habits, alcohol intake, HEI scores, and colonic segments.
Microbes were classified based on the amplicon sequence variants (ASVs), and alpha diversity was assessed using the Shannon index. The team excluded individuals having inherited polyposis, inflammatory bowel disease, invasive cancers excluding non-melanoma cancer of the skin, and those with polyps in colorectal tissues in the prior 3.0 years.
In addition, individuals with advanced kidney disorders and dialysis requirements, severe mental disorders, hospital admissions in the previous year, systemic or oral antibiotic use in the previous 3.0 months, and a history of hepatitis B virus (HBV) or hepatitis C virus (HCV) infection were excluded.
Further, individuals with a history of methicillin-resistant Staphylococcus aureus (MRSA) infections, human immunodeficiency virus (HIV) infections, and those contraindicated from undergoing mucosal biopsy were excluded.
Results
Initially, 612 individuals were recruited for the study, and from 174 individuals with healthy colons, 134 were willing to undergo colonic biopsies. Specimens from 69 healthy individuals underwent microbiome profiling, among whom 40 responded.
Five individuals consuming <800.0 or >5000.0 kcal daily were excluded, and thus, data from 99 colonic mucosal specimens obtained from 35 individuals were analyzed.
The exclusion of poor sequencing data from two colonic biopsies, including one biopsy from an individual, reduced the sample size to 97 biopsy specimens from 34 adults. The mean caffeine intake among individuals with low and high caffeine consumption was 39 mg and 139 mg, respectively.
Regular riboflavin intake was significantly greater among individuals with high caffeine and coffee intake. Greater caffeine and coffee consumption was related to greater alpha diversity, elevated Alistipes, and Faecalibacterium counts, and lowered Erysipelatoclostridium counts.
On a family scale, compared to low caffeine intake, a high caffeine intake was associated with increased Ruminococcaceae and decreased Erysipelotrichaceae abundance.
Genus-level differences included a greater abundance of Alistipes, Faecalibacterium, Prevotella, and Subdoligranulum, and a lower abundance of Lachnospiraceae (ASV0006) and Erysipelatoclostridium among individuals consuming caffeine in high amounts.
The incidence rate ratio (IRR) values of non-zero counts of Alistipes and Faecalibacterium were 3.1 and 5.3, respectively, greater than those for having non-zero Erysipelatoclostridium count (IRR 0.1) among high caffeine consumers than low caffeine consumers.
High coffee consumption was related to elevated Alistipes and Faecalibacterium counts and lower Erysipelatoclostridium counts, with IRR values of 2.8, 2.4, and 0.2, respectively, compared to low coffee consumption.
Adjusting for riboflavin levels, caloric intake, and BMI yielded similar IRRs; however, attenuated values for the relationships between Alistipes and Faecalibacterium abundance and coffee and caffeine intake were observed. Erysipelatoclostridium counts were significantly and inversely related to caffeine consumption (IRR 0.02).
Conclusions
Overall, the study findings highlighted significant differences in colonic mucosal bacterial colonies concerning the structure and composition based on regular caffeine and coffee intake among adults.
Greater caffeine and coffee intake was associated with greater evenness and richness of the colonic microbiome, with increased Alistipes and Faecalibacterium abundance and lowered Erysipelatoclostridium abundance.
The health benefits of coffee consumption may partially be explained by prebiotic riboflavin. Further metabolomic and nutrigenomic research is required to identify individuals likely to gain maximal benefit from coffee. Improving our understanding of the associations between phytochemicals, nutrients, and intestinal microbiome could unravel novel mechanisms for preventing disease.