Impact of beer and non alcoholic consumption on the gut microbiota
By Pr. Bernd Schnabl
Division of Gastroenterology, San Diego Digestive Diseases Research Center (SDDRC), UC San Diego, USA
About this article
Alcohol is known to affect the gut microbiota. Larger amounts of alcohol (e.g., more than 2 drinks per day for men and 1 drink per day for women) have negative effects on the gut microbiota, which is accompanied by a decrease in bacterial diversity and an increase of potentially harmful microbes. However, the effect of moderate alcohol consumption on the gut microbiota is less known.
What is your opinion regarding the fact that nonalcoholic & alcoholic beer increased gut microbiota diversity, which has been associated with positive health outcomes?
Does that mean you could recommend your patients to drink 330 mL of beer every day? A recent randomized clinical trial investigated the effect of one daily beer (330 mL) with alcohol (5.2%) or without alcohol (0.0%) during a 4-week period . Twenty-two healthy men were enrolled and the fecal microbiota was assessed. Bacterial diversity increased when baseline stool was compared with samples collected 4 weeks after the intervention in each group. However, diversity was not different between subjects consuming alcoholic or non-alcoholic beer. As the only difference between the two groups was alcohol, other substances present in both beverages might explain these differences. Bioactive compounds such as polyphenols and phenolic acids, which are present in alcoholic and non-alcoholic beer, might have a positive health effect possibly mediated via an increase in bacterial diversity. Some of these bioactive compounds develop during the brewing process and can originate from hops or malt. Bacteria in our gut are known to metabolize dietary compounds and might utilize them for their own metabolism. More experimental evidence is required to determine the effects of these bioactive compounds on gut bacteria. Ideally, such a trial should be done in a larger cohort of subjects who do not consume alcohol at baseline.
More studies are required before a recommendation for daily consumption of one beer can be made. This should be preferably non-alcoholic beer as alcohol, even in small amounts, has been associated with worse health outcomes.
How do you explain that drinking nonalcoholic or alcoholic beer daily during 4 weeks did not increase body weight and body fat mass and did not significantly change serum cardiometabolic biomarkers?
Comparison of the nine subjects in the non-alcoholic beer group versus ten subjects in the alcohol containing beer group finishing the aforementioned study showed largely no differences on liver function, inflammatory or metabolic markers. There are several possibilities why increased bacterial diversity did not translate into improvement of these markers. The study duration might have been too short and the number of participants in each group might have been too small. Although subjects in both groups were overweight, most other markers were within normal range. It would therefore be interesting to assess the effects in patients with metabolic syndrome, whether there is an improvement in intestinal dysbiosis, increase in bacterial diversity and a concomitant improvement in metabolic parameters.