A recently published scientific report supports a long-existing theory that the antioxidant capacity of beer polyphenols may induce positive shifts in gut microbiota composition. The report titled “Effect of Moderate Consumption of Different Phenolic-Content Beers on the Human Gut Microbiota Composition: A Randomized Crossover Trial” was published in ‘Antioxidants.’
Moderate alcohol use has been linked to some positive impacts on metabolic and cardiovascular health. Malt and hop polyphenols in beer may, among other things, help to protect the cardiovascular and endocrine systems.
How the Study Was Conducted?
A randomized open-label crossover trial was done for this investigation at the Virgen de la Victoria University Hospital in Malaga, Spain. This study comprised adults between the ages of 30 and 60. Exclusion criteria included morbid obesity (body mass index 40 kg/m2), drinking more than 30 g or 20 g of alcohol per day, and taking antibiotics, prebiotics, probiotics, vitamin supplements, or other medications that might affect the composition of the gut microbiota.
Participants were not allowed to consume alcohol besides what was provided, vitamin supplements, probiotics, prebiotics, antibiotics, or other medications that might impact the microbiota during the study intervention. Subjects with metabolic syndrome and healthy volunteers (all of whom had BMIs under 30 kg/m2) made up the two groups of volunteers. A total of 20 participants (10 healthy volunteers and 10 subjects with metabolic syndrome) aged 30–60 years old were included in this study.
Participants were randomly assigned in a crossover design to determine which of the three therapies they would receive after a 2-week washout period: Three types of beer were tested for polyphenol concentration using the public database Phenol-Explorer: (1) Alcohol-free beer (low polyphenol content—12.2 mg/100 mL); (2) Lager beer (mid polyphenol content—27.83 mg/100 mL; 4.2 percent ABV); and (3) Dark beer (high polyphenol content—41.6 mg/100 mL; 4.5 percent ABV).
For each trial, a 33-centiliter bottle of the right beer was consumed daily for two weeks. Blood samples were obtained following a 10-hour fast. The biochemical parameters were measured using conventional enzymatic methods. A measure of glycosylated hemoglobin and C-Reactive protein was taken.
What Are the Key Findings of This Study?
It is interesting to note that only the group with metabolic syndrome showed the primary alterations in the study population following the various therapies. As a result, after the three therapies in this group, glycosylated hemoglobin (HbA1c, percent) somewhat decreased, but uric acid levels dramatically increased (within normal serum levels). On the other hand, healthy volunteers’ HDL cholesterol levels slightly rose after consuming dark or lager beer.
Alterations in each beer intervention with regard to the washout period were evaluated in order to better understand the changes seen with each type of beer. The microbial population at baseline and dark beer were found to be significantly different. Significant alterations were also discovered in the Streptococcaceae family and the species Streptococcus. There were no variations in the intake of beer without alcohol.
In healthy volunteers, there were no discernible differences between the baseline and the dark beer/lager beer/alcohol-free beer interventions. However, persons with metabolic syndrome tended to have higher relative abundances of Streptococcaceae and Streptococcus and lower relative abundances of Actinobacteria and Christensenellaceae after beer consumption, while Akkermansia generally reduced its relative abundance with beer consumption.
What Is the Importance of This Study?
In this randomized study, it was demonstrated that prolonged moderate beer consumption causes numerous alterations in gut microbial composition. Additionally, these modifications are influenced by the type of beer ingested because they become more noticeable after drinking dark beer (high polyphenol content). Furthermore, some of the changes in the relative abundance of various gut bacteria that have been noticed after drinking beer seem to be connected to the host’s metabolic state.
References
Martínez-Montoro, J. I., Quesada-Molina, M., Gutiérrez-Repiso, C., Ruiz-Limón, P., Subiri-Verdugo, A., Tinahones, F. J., & Moreno-Indias, I. (2022). Effect of Moderate Consumption of Different Phenolic-Content Beers on the Human Gut Microbiota Composition: A Randomized Crossover Trial. Antioxidants (Basel, Switzerland), 11(4), 696. https://doi.org/10.3390/antiox11040696
